c-/u
Tf-XE ~~87 /SE"86
P~TIO
CONTIt-m!~hL
It~ OCEAf.\lIC AND
BASALTS jU~D THE
or.J:GI~~ 0'2 IGtmOUS ROCKS
by
GtJN1rER FAURE
B.Se., Unive~sity of Westezn Ontario
(1957)
)
LI ..~~~
, .1NDGll£N
SUBl'-D:TTED IN PA1:tTIAL fMJI2ILL!i1ENT
OF THE REQUIlRE.I'f~~""TS FOR THE
DEGREE OF OOCCrOR OF
PHILOSOPHY
at. tha
MASSAChVUSEftS ImSTITUTE OP
TECHNOLOGY •
June, 1961
Certified by
~
,
-
Thesis Supervisor
-
t
.
Accepted
by
----------------Chairmal1, Departmental
Committee
of G~aduata Students.
THE Sx-81jsx-86
RATIO IN OCEAtilIC Al~D CO~~!~m~""X'AL
!3ilS}~LTS 1\~'"D ~'HE ORIGlt~ 01'1 IGNEOUS
by
ROCI(S
Guni:er Fat!X"e
Submit~ed ~o the Depa~~~en~ of ~~ology snd Geophysics
on May 15# 1961, in paztial fulfillment of the requi~e~
ments fo~ ~he aegree of Doctor of Philosophy.
Abst~
The isotopic
eqmpositions
of strontium
in 2S basal~s
and related volcanic rocks f~~~ oceanic and continental
localities
have been detG!!~linedtl
the abundance of srS7 in basal'ts.
ratio, is constant Wi~li~ n~rzow
of the sr87/sr86 ratios of eleven
teen cQiil'tinental basalts
0.0003c respectively.
'Arne &"esults indicate
'\.':ha't
67
e~tpg'es:;edas the SX ;S'IC86
11mi~s. The average values
oceanic basalts and ~our-
arc O.7072:t 0.0003 and O.70B2.:t
The diffe~ence in ~he abundance of
Sr87 is not consis~ent and is not believed ~o be signif1can~o
The overall average sx8ils~86 ra~10 xor all 2S basalts is
o. 707a~g:gg~.
1\ reproducibility
of:t 0.001 (.14%) fox- t'he
87
sr /sr66 ratio was acbieved by making an 1nst~uw~ntal isotope fractionation correc~ion. The accuracy of the ir~asure~
manta W&S monitored by periodic analyses of a srco3 standard.
The concentxa~!onB of rUbidiam and strontium in a rep~~~
sentative number of basalts were dete~~ned by isotope dilu~
tio~.
Five olivine basalts avezaged: Rb =17 t. 6 ppm,
Sr
390.t 55 ppm, RbISr :: Oe044:t 0..018 whereas six t.hcleeitic
basalts were found ~o contain 30~ 7 ppm Rbi 504% 167 ppm S~~
Rb/sr = 0.060% 0.024.
The ~epzoducibi11ty
of the rubidium
=
and atgon~ium analyses is~ 2%e
The small, but statistically significant, diffe~ences in
the abundance of sr87 in basalts from different locali~ies
are in~erpreted as evidence of small latexal and/or ve~tical
variations in ~hs Rb/Sr ratios of the source material of
basalt magma. Numazical values of the Rb/Sr ratio w~~e cal~
culated with the assumption that the initial Sr87/Sr86 ~atio
was O.7004Z 0.002 and that the age of the source material i6
4.5 x 109 years. The average value and its limdts of varia-
= O.039~8:8i~.
tion was found to be Rb/Sr
The relative
abundance of rubidium in the souzce regions of basalt magma
is therefore approximately iden~ical to ~hat of olivine
basalt, eclogite or ul~rabas1c 19naous rocks. The low value
of ~he Rb/Sr ratio
as "Jell as other geophysical
and geochemi.-
cal evidence suggest that basalt magma is ganerated
upper mantle.
in the
The abundance of sr87 in the sialic CZU6~ waa estimated
by making reasonable assumptions about 1~B Rb/Sr ratio, its
age and its initial sz87/sr86 ~atio.On the basis of the mos~
reliable rUbidium ana stz~ntium analyses available in ~he
geochemical literatuze and using PoldervaaztOe crustal model,
~he Rb/sr ratio of ~he sialic crust was estimated to be Oe25.
If its age is 2 billion years and its initial sr87;srB6 ratio
was 0.704, the pzesent value would be 0.725. This es~1mate
~aB substantiated by ~e results obtained for two composites
of Paleo2oic shale which averaged sr87/sr86::
0 7215 Z 0.001.
'I'his value is measu&"ablyhighsr than that. in oceanic and
continGn~al basalts.
CI
On the basis of ~h1s evidence the hypothesis is advanced
'that the value of tIle sr87/S'1:86 X'atio of .igneous rocks, at.
the time of crystalli~ation, can be used as a crite~ion fo~
the origin of the ma~erial. The initial sr87/sr86 ra~io o~
an igneous rock formed by ~e-msl~ing or gzanitization of
sialic mategial is expected to be measurably higher ~1an
that: of an igneous rock dGlrived frem the souX'es regions of
basalt magma.
~e initial sr87/sr86 ratio of.a complex of intrusive
igneous ~oc:ks or of .a series of lava flows of different.
compositions is best dete~ned
from the coordina~es of the
point of convergence of the wholG-gOCk st:ontium development
lines. The convergence of the strontium developmen~ lines
is a teet for possible co~agm&t!c relat.ionships of associated igneous rocks. This teat is particularly applicable ~o
the study of alkaline rocks, pegmat1tes, lamprophyres and
cl1roonatites.
A pre11mdnary investigation of ~ha 1n~ruBiva igneous
roclts of 'the Monteregian hills, Quebec, indicated ~hat the
different: rock t.ypes were derived from f:he sa..~ source about
11Sr 2S million years ago which.at that time had a Sr87/sr86
ratio of 0.7047%0.001.
This unusually low value indicates
tha~ these rocks originated in ~he source regions of basalt
magma, perhaps well belo"J the base of the crust.
Thesis Supervisora
Titles
l?atrick M. Hurley
Professor of Geology
page
2
12
LIST OF TABLES
16
18
ACKNOWLEDGIl/lEil'STS
Part I
TPu~ BE'87/S;g:86 RATIO It" OCEIUnC ,At'ID COI~Ii:-mm'AL
BASAI.,TS ~JD '.rHE ORIGIN OF IGNEOUS PDCKS.
Abstract
20
Iratroductlon
21
E~~erimental Errors and Accuracy
2S
Analytical Data
30
The Isotopic Composition of Strontium in
the Source Regions of Basalt Magma
36
The Isotopic Composition of Strontium in
the Con~inental C~ust
41
Geological Applications
49
Evidence of Sub-crustal Origin of the
Intrusive
Hills,
Igneous Rocks ~.n the Mont.ereg1an
Quebec
Discussion of E)~er1mental Results
54
56
Conclusions
61
Acknowledgments
64
References
6S
Page
1?a~t
II
Chaoter
1
V~RiAT!ONS OF THE sr87/sr86 RATIO IN ROCKS AND
THEIR GEOLOGICAL SIG1:1!~IChl~CE.
70
Introduction
Derivation
Equation
of the strontiwn
Development
73
The Primordial sr87/SrB6 Ratio
78
C~ol09ic&1
83
Applications
The Origin
of Granitic. Igneous
84
Magma
90
of the Upper Man~le
93
The Differen~1ation
The Composition
Rocks
of Basalt
ChapteE' 2
THE COUCENTRATIONS OF RUBIDIUM AND STRONTIUM IN
IGNEOUS AtID SEDIMENTARY ROCKS AND IN THE CRUST
OF THE EARTH.
Introduction
95
~le Concentrations
of Rubiaium
in Igneous and Sedimentary
and strontium
Rocl~s
96
Summary
107
Summary and Conclusions
113
-.
The Concen~rationB of RUbidium
in the Crust of ~le Earth
and Strontium
11($
Introduction
POldervaart's
Model of the Crust
Introduci:ion
118
119
Continental
~~ield Region
121
Young Woldea Eelts
122
SUb-oce~nic
124
Regions
Volcanic Islands
126
The Crust ol the Ea~th
127
Summary and Conclusions
130
Chapter 3
THE ISOTOPIC
COz.mOSITI01,J OF STROmZU~1 IN TIE
CRUST OF fl'EEEnRTH.
133
Int.zoduction
The Isotopic Composi~ion of St~ontitffil in
Chemical Reagents and in Ocean ~;ateZ'
134
Estimate of the sx87jsz86 Ratio in the
Crust
139
Egpezimental
142
Evidence
Summary and Conclusions
144
Chapter 4
RUBIDIUM
AND STJaONTXUf.l ]\l~t,YSES.
145
Intzooduction
Experimantal
pzocedures
Preparation of Br8S Radioactive Trace~
Calibration
147
of the "Spiltec,a Solutions
Introduction
RubidiQ~
145
Bnd Strontium Shelf Solutions
149
151
152
P~eparation of Dilute Rubid! lLtU Spilt8
Calibration
of sra6 Spik~ Solution
Calibration
of
Precision
S1:84
of Rubidium
Sp1Jte.
154
155
158
and Strontium
Analyses
Introduction
Rubidium
Chapter
160
and Strontium
Blanks
160
Results of Triplicate Rubidium and
Strontium Analyses
162
TiltonOs
164
Rubidium
Shelf Solution
5
MEASURENEN'T OF THE ISOTOPIC
OF STRONTIUM.
COMPOSITION
Introduction
166
Chemical Procedures
166
Mass Spectrometric Techniques
170
Discussion of Er~ors
174
Introduction
Reproducibility
175
1\ccuracy
180
Conclusions
183
Chap'te&' 6
TEfE ISO~'OP!C
CC~~OSITIOt;j
AtiJDCONT!NEN~AL
OF STROt~~rXnz-! IN CCEIHG!C
BASArmS~
185
Analytical
187
Resul\.:s
lee
Oceanic Basal'ts
loSS
193
t?1sCOrt'3sion Isl~nd,
and iGhe l1z0~es
!!'.doeuAtlantic
Ridge ~
1.94
195
197
Continen~al Basalts
197
Daccan Plateau~ India
201
Columbia Rive~ Plateau, Oregon
202
Triassic Diabases of New Jezsey
and Connectic\}.t.
203
!~ecellanaoua Localities
204
205
206
Conclusions
Chapter 7
THE sz67/sz86
IU\TIO It~ PRECA!~r~AN
BASIC I~f1'RUSlVES.
210
Introduction
Tho Bushveld Igneous CGmpleJ~1
Introduction
s.
Africa
211
page
211
E:tpmximeni:al Results
213
Discussion
21.4
Conclusions
217
erne
Duluth Gabbzo
Introduction
E~erimen~al
211
Results
218
Discussion
Slurnnaxy
and Conclusions
Cllap'ter 8
Part 1
THE AGE OF AN ECLOGITE BY THE Rb-Sr
)1ETIiOD.
Introduction
~23
App~ica~lon of ~undances of 'Strontium
Isotope~'in 'Basalts to th~ Eclogite Problem
226
Geological Summary
227
Exper1~n~al Data
227
Diacussionof the Results
230
Conclusions'
232
part 2
.
'
THE
THE AGE OP
FOmlATION
~Et..Y GREENSTOtiE
~"D
..
T$
SOUDAN
I!l MINNESOTA •.
Introduc:1:ion
233
Geological Summary.
233
"
.
Experimental
Results
235
235
Discussion
239
pag~ 3
ElJIDEt~CE OP SUB-CRUSTAL OR!GIF! OF ROCI{S rfROr.-1
THE I~OI~EREGIAtq
LLS s QtJEB;E;C..
m
24-0
Geological Summary
240
242
242
Discussion
247
Conclusions
Chapter 9
VARIATIONS OF THE sr66/s~B9 At~ s~s4/sza8 RA~IOSo
249
Discussion of Re8ul~B
252
251
Conclusions
Chaptez: 1.0
DESCRIPTION OF S~!.iPLES.
Oceanic Basalts
Con~inental
Volcanic Rocks
precambrian Easic Int~sives
Monteregian
Hilla
262
264
264
Eclogit.e
265
tt~ewat1n'Volcanics 2r~~ Minneso~a
Shale Composi~es
265
266
BIELIOGRAPliY
267
BIOGRAPHY
2i7
26
Isotopic Compositi@n of St~on~ium in
St~ont1um Reagen~so
A~~lyt1cal Resul~~ for Oceanic
~a
·
'co~tinental ~aealtso
26 '
31
Concentrations of fu~oid1lnn ~nd St~ontium
in.Igneou$ an.d Sedimentary RockeD
~~ncentra~iona of Rubidium and Strontium
in the Crus~ as Defined by polaezvaag~Os
~-5
45
tttCdel.
Estimate of the sr87/sr86 Ratio in a
aypotbe~ical Geos¥nclinal ~ssemblage.
46
Iao~op1c ComposltifJO of Strontium in
Composites. of paleozo~c Shale'.
47
Isotopic C~positicn
Qf St~ontium in
Igneous Rocks frQftl the Monteregian Hills.
57
1.1
The PZ"imoZ'dl~ls~87/sr~6 'RatiO.
80
1.2
Initial sr87/sg86 Ratio in Chondritic
Meteorites.
82
2.1
Superior'Analyses of Rubid1um and S~rontlum
in Igneous" Rcc'ks and Meteorii;ss. '
97
P~t
II
Table
2.2
Summary of Rubidium and Stron~itim Concentrations in Igneous Rocks •.
106
2~3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2~11
2.12
2.13
1
Supe~ior nnalyseBof Rubidium and
Strontium' ~n Sedimen~ary R~eka9
110
Surr~ar~of RUbidium and 8tron~iw~ Concen~r&tions in Sedimenta~ ~ockse
114
and S'tron'cium
in Igneous a.nd Sedimentcu:y Rocks.
115
Concentrations of alm1dium and' Strontium
in '~he Oceanic CZUBt.
120
Concentrations of Rubidi~~ and Strontium
in the ~ontinental Shield.
122
Concentrations of Rubidi~~ aridSt~ontilli~
in the Young Folded Belts.
124
Concenerations of RUbid1wn,~,d Strontium
in ~he,Sub-oceanic Regions.
126
Concant;gat1.ons of ~ubiaiu.li'Q
Concentrations
of Rubidium
and Stronti~~
in OCeanic Xslands.
127
Concentrations of RubiCliumand Strontium
in the Total Crust.
128
Concentrations of Rubidiumahd St~on~lum
in Various l?ari:s of' 'the Crust.
129
Concentrations
of Rubidium and St~ont1um
in 19n~ous and sed!ment'ary ttocks.
2.14
Concent~at1ons of Rubidium and strontium
in the Crust.
3.1
131
132
Isotop1eComposj.t1on of Strontium 1"
Ch~m1cal R&agen:~ts.
135
302
Isotopic Composition
of Sea Water Strcnt1um~
3.3
The sr87/sr86 Ratio in a:ayPotbetlcal
Geosynclinal Assemblage.
136
141
3 ...4
:!8~~i't:~pd.cCert~p"osi'~~.<n~
of: S'ti.:Z'Qn:citlE'..l i7tj
C~28tal
RG~ks
B
•
152
~
Gp;lke(l
lmalytical Da:ta ffnr: Calib~:a:;;i@!j o~: S~.86
(
t.L,4:
156
j~ilalyt:tcal Da'ta
£04'
~.....
84
Calibza~~ ..cl1 of ~.'.'..
monaal
and
S'tt:on1::il:L>Q Elmn"tt D'8t(tn~111iwa"i::tcw~z
Rub:tdifl:sG
SpjJ{f9 ..
159
Q
161
lIr].agn1-cudeof
RlWidiu.,~ and Stzon'tium
131a~1!~
161
Co::goc'i:ions.
4.6
165
4.7
Inte~la1)CEa,toz" ~u~st.11.tsfor T!l'ton 0 s l~ubidilliu
Sh~lf soluti\c)1!lt.
5..
1
Isotopic
165
Composition of S1:E'ont:j.'
..un in Basalt
from RilauasD
Hawaii (R1292).
St~ont1Um Carbonate Reagent~ Eime~ and
181
P~end, lot 492327.
5.3
!sotepic Composition cfSt~onti~n
~eagants.
'
O~ean1c ~asalts.
in G1s~cal
'
182
139
6.2
6.3
7.2
Continentat
Ozigin.,
Volcanic RO.9kf3
of Sub~czustal
198
Summary of Data fo~ Continental Saaalts at
~he Time of ?~eir Ex~ru5!on.
205
The Bushveld 'Comple~tl!;
215
DUluth Gabbi:c..
220
Page
228
The Ely Ggoeenstong and t.he Scud~n
~omation.
8.3
E:~rimantal
236
Results fo~ the Mcntegog1an
Hij~ls, Quebec.
243
250
9.2
Chi Square 'lest.
256
-16<::>
LIST OF FIG~ES.
Figure
A-l
Page
The sr87/sr86 Ratio in the Source
Regions of Basalt. A-2
41
The sr87/sr86 Ratio in the Source Regions of
Basalt Magma and in the Sialic Crust.
A-3
The sr87Jsr86 Ratio in the Intrusives of the
Monteregian Hills, Quebec.
1.1
58
Increase of the sr87/Sr86 Ratio with Time
and the Rb/Sr Ratio.
1.2
Sl
77
sr87/sr86 Ratio in the Crust and the
Upper Mantle.
85
Concentrations of Rb, Sr, K and Ca in
Igneous ~ockso
108
Sr Development Lines for Red Granite,
Bushveld Complex, South Africa, Schreiner,
1958,p. 114.
212
The Basic Igneous Rocks of the Bushveld
Complex,S. Africa.
216
7.3
Duluth Gabbro
219
7.4
Initial
2.1
7.1
7.2
sr87/sr86 Ra~1os
in Precambrian
Basic Intrusives.
222
Eclogite Xenolith from Kimberlite Pipe,
Robert Victor Mine, South ~frica.
229
8.2
Ely Greenstone and the S~udan Foxmation.
237
8.3
Monteregian Hills
244
9.1
Distribution of
8.1
sr8G/sraS
Ratios.
251
-17Figure
902
9.3
Plot of Cumulative Distribution of the
sr86/S~88 Ratios on Normal-Probability
paper.
Distribution of sr84/sr86 na~ios in Rocks,
Tektites and srC0
3
8
9.4
Plot of Cumulative
Ratios.
_
Distribution
254
258
of s%84/sr88
259
It is a pleasure to acknOwl~~ge my~ebt.to
my ~hesis
,suppliec1 most of 'the r:;>ck specimens and' made ava11abl~ a
.' ,mass spsctrameter
for
'the analyses.
His comments and
constructive suggestions did ~mch to clarify the problem
and k~pt the investigation on a t~ue course. 'In addition,
I wish to thank ~rof~ssor
t~"H..
Pin~on,
,
the chemical procedures and inst~~ental
','
'\JJhotaught
J-&.,
,
'
..
me
,
,
techniqu0s many
Fellaw students have con-
of which h~ developed himself.
tributed to many aspec~,~~~ th~s ~h~sis throug~ 1nformal
a1scussions
, endabted
comments. ,I am"pa.rticularly
and 'crit~c~l
to Dr. S.R~ ~art,. Mr. C.C. Schnei:zler
and Mr.
G.R. Beall ~ho in 'add~tionsuppl~ed several of tbe rock
,s~c1rnens from the Monteregian ~ills. ,I als~ wish to
thank.Professol: J.D. Thompson, Jr. ot Harvard Univex:s1ty
...
'
...
'for ..the. rock 'specimens f:tom,the.. Bushv.eld Complex~
I
.
.'
"
"'11\18 'thesis
w~~
the
full'
was in, fact
of
cooperation
a
my
.
•
joint ven~ui:~u~dertak~n
wife Barbara
to .whom I
'OWe.a large debt of 9rat~tude;
.' The financial,.support of Imperial Oil Limited
.
,
throug~ an Imperial
Oil Graduate 'Research
9ratef~11y aCkno~led9~d.
~ellol"ab1p is
(Intendedfo~ Publication)
~pm S~~/SZ86
RATIO IN OCE~r~C
CONTlNE1~AL
B.r.~LT
nt~
THEl
AND
2RIG1N OF IGNEOUS ROC~S.
By G. Faure and P. ~1.Hurley
0
Abstract.
Tne isotopic
compositions
of ~trontium
in 25 basalts
and related volcanic rocks from oceanic and continental
localities have been deterMined.
The results indicate
that the abundance of ar87 in basalts, expressed as the
Sr87/sr86 ratio, is constant within narrow l!mi~s.
The
87
86
average values of the Sr /sr
ratios of eleven oceanic
basalts and fourteen continental basalts are 007072+
0.0003 and O.1082.:t0.0003, respectively •. The diff"erence
in the abundance of sr87 is not consistent
believed to be significant.
ratio is 0.7078 + 0.002
The overall
and is not
average Sr87/sr86
-0.003.
The concentrations
representative
of rubidium and strontium in a
number of basalts. were dete~ned
by iso-
Five olivine basalts averageas
Rb
17.t 6 ppm,
Sr = 390 T. 5S ppm,
Rbis!:' 13 O.044.:t. 0.018
whereas six tholeeltic basalts were found to contain
tope dilution.
=
301: 7 ppm xu"
.
504:!:.167 ppm Sr,
Pb/sr
ciJ
Oo060:t
0.024 •
The small, but statistically significant, differences
in the abundance of sx87 in basalts frcm d1fferen~ locali-
ties are interpreted as evidence of smull lateral and/or
vertical variations in the Rb/sr ratios of the source
regions. Numerical values of the Rb/Sr ratio were calculated on the assumption tha~ the initial sr87/sr86 ratio
~)as O.7004:t 0.002 and that
4.5 x lO~ years.
variation
the age of the upper mantle is
The average value and ii:s limits of
was found to be Rb/Sr
t1ve abundance of rubidiam
magmais therefore
s
.
0.039+ 0.012.
-00017
The rela-
in the source regions of basalt
approxima~ely identical
to that
of
olivine basalts
;or ecloyite.
On the basis of~he mos~ reliabl~ rubidium and stgontium analyses of.igneous and s~imentary'roeks available
from the 11teratur~ .arid ,-,sing Po~dervaart 0'8. . crustal' model,
the RbISr ratio of '~he .sialic cZust' was les.tin\~ted to be
(L.2S. ,If the age of1:he sialic crust 1'6,approximately
2 b111i(~n yearsand1ts
initial sr87/Sr86,' ratio was 0 •.704,
the'preB~nt ave:age value woul~ be. 0.725. This estimate
was substantiated by the results 'ob~a1ned for two composites of Paleozoic shale which averaged Sr87/srB6
0.7215
+.
_.0.001.
'
'
=
.
On 'the basis of this evidence-the hypothesis is
advanced"that the value of tIle sr87/sg'86 ratio of igneous
ro~ks',. at 'the t1~ of cry~t~11i2at!on,
can be used. as a
criterion for.the origin of the materialo
Th~' initial
S7
86
,sr /sr
. ratio "of an igneous rock formed by re-me 1ting or
9rani~za~1on of ~e sialic C~ust is expected to be mea~ur~
al3.lyhigher thantba,t. of atf .igneous ~ock °d,erived from the
sub-crustal
s~urqe',z.e910ns o~ basali: magma.
sr87/sr86 ratio' of a 'complex of intrusive ~tjneo~s .rocks,,or of a 'series of lava flows of differ ..
'theinit.ial
-ant' cotnposltions
vergenr::e Of t.he
The' cori"ergence
'also ~ .used to
betwe«:tn
is bestdeteJ.:lD1ned from the point
of 90n-
whole~3:oclt strontium development
l.ines.
lines can
'
of i:ho strontium development
test f~r pOssible co-magmat:1.c.
rela-t1onships
8l3S0c1a'ted igneous, rocks.
I~
is suggested
that
this f.t9thcd 1s particularly appl~CaPle to 'tbestudy of,
.alkal~e r~ks, pe9ma~ites, iamprophyres' andcarbonatites.
Introduci:1on::
..'rile abundanc;e
of sra7,
expressed' as the 'ra't10
sr87/s~86! has increased by'the nat:u~ai'rad~oact1ve'decay
of Rb87 ~o s~7
since the tlmeof
formai:ion of the eleIr~nte.
The J:;81:e'of 1ncreaB~ of 'the srS7/s.r86
ratio: of any system
Whicb' is",close''' to rubidium andstront:1um
duri~9
it:s,11fe-
time is propo~ional
to its RbISz ratio.
pgocesaaa opezat1ng si~ce ~e
have X'Gsulted in an enrichment
Differentiation
beginning of geologic time
of rubidium .in the upper
regions of the con~1nental crus~ relative to the base of
the crust and the upper ma~'tle. As a result: tot is
expected that in the course of geologic time the abundance
of
sr87 in the sialic crust has increased at a greater
rate than in those parts of 'the upper mantle which are
the source regions of basaltic magma.
If the difference
in tha sr87/sr86 ra~1os of the two environments
is
measurable, then the origin of intrusive ~9neouB rocks
in the sialic crus~ can be de~erm1ned
of their sr87/sr86.ratios
In1:rus1ves wh1chwere
from tbe values
at ~he time of crystallization.
formed by re-melt:ing or grani't1za-
tiOD of sialic material are expected to have higher
Sr87/sr86 ra1:ios than ~hose igneous rocks which originated
in the upper mantle or the lower: s1mai:1cregions of the
con1:1nen~al crust.
A very similar
BU9ge'stlon
was made by Holmes
who proposed t:hat: the abundance of the isotope
could be used to differentiate
bet"-rreen grani tee
(1932)
ca41
formed
by recme1t!ng of granitic parent material from those which
are derivatives
of basalt: magma.
This pE"oposal was based
on the asaump~ion, now diapZ'ovedo 'that ~l
The abundances of the 1S0~OpeC3
~ela~1ve to SraG
= 1, as
decays to Ca41•
Sg87 and Rb87, both
a function of time in any system
which rema1ned closed ~o rUbidium and s~rontium during ita
lifatims
can be expressed as foll~ ...
er:
).-t"
a ~ ao+ b(e
(1)
-1)
whe:e
a
b
=
sr81/srS6 at time of analysis of ~e ma~er1al
=
Rb87/sr86 at time of analysis of the material
sr87/S:86 at an 1n1~1al t1me'~c
=
~1me measured backt:tJ8rds from
A =
'the present
decay constant: of llb87
1.47 x 10-11 ygS-l (Flynn and Glendan1n, 1959)
-
Before equation
(1) may be used to calculate
the abundance
of ar87 in the sUb-crustal source regions of basal~ magma
th:rOU9hou~ geologic time, appropr1ai:e values of
musi: f1rs~ be determined by a judicious
available
data.
:reg1ons wi~
80
and to
examinat:1on of
Moreovez, the homogeneity of ~he source
respect: to 80 to to should
be
demons$:rated.
In this paper ~he xesul~s of 1sotop1e analyses of
strontium in 2S basalts and related volcanic
sub-crustal
oriq1n are reported.
rocks of
The specimens were
selected from oceanic and continen~al
to test the lateral h~gene1~y
localities
in order
of the sub-crustal source
regions of basalt magma with respect ~o a, the present
sr87/sz:86 ra:tio.
The resul'ta will
order to dete~ne
also be exa.c...wrdnad
in
to wha~ extent they 1nd1ca~e homogeneity
of the source regions with respect to So and to.
Concentrations
of rUbidium and strontium were meas-
ured in a representative
of isotope dilution.
for their
numbaX' of baaali:s by the method
These analyses were made not only
geochemical 1nteresi: but also in ordaZ' to
compare the measured values of the Rb/Sr ratios in
basal~s to ~hose of their sou~ce regions calculated by
means. of equa'tion (1). Such comparisons can give evidence of chemical fractionation
ing of the source material
Experimental
Errors
during ~e
partial melt-
to produce magma.
and Accuracv!!
All 1'il88SUremen1:&were made on one 60° sector
radius"
solid source mass spectrometer
sweep and a vibrating ,ree~.electrometer
tion of ~e
lon current.
D
6 inch
using a magnet
for amplifica-
The instrumen~ was built at
M.I.T •. and has been described
(1958)" and Herzog and Pinson
previously
(1956).
by Herzog et
al.
Xt ~as dasi~able for the pu~osa
of this investiga-
tion to determine Sr87/Sr86 ratio3 with a reproducibility
of O.l~ or better and ~o ma1~~a1n a high etsndard of
accuracy of all measurements. The geproducibil!~y of
the mass spectromatglc
measurements
was determined
from
the resul~s of "several analyses of a single sample repeated
peIClodically throughout
the course of this investig&tion.
It was expressed as the standard deviation for a single
analysis calcula~ed fram the results of the replicate
analyses.
Tha main fac'tors
duc1b11ity are:
during che~cal
spectrometric
t1h1ch c1etexmine ~he X'spro-
variable amoun~9 of contamination
processing of ~he samples and the mass
analysis,
effects of isotopic
fractionation
in the 1ns~rument., vaz:1ations of ~a
ra~e of ion emission
from the fl1amen~, 1nstabili~y of ~s
magnetic field of
the magnetic
analyzer
in the amplification
and high-f:equency
and recording
electronic
noiee
systems. Several of
the errors listed above may bs systematic
for a single
analysis but are random for a large number of repeated
measurements. They thus affect
single determination
Z'~ndom errors.
the xeproducibility
and are "included with ~he truly
of a
An instrumental
fractionation
corgection
to all sr87/sr86 ratios on the assumption
ratio is a constant e~al
was applied
~hat the Sr86/sz88
to O.1194(Nier, 1938).
All
szS6/sr88 ra1:ios were adjusted to this value bu~
measured
only half of this correction
was applied to the measured
sr87/srS6 ratio bacauss the mass difference between SrB7
and sr86 is only one half
~a~
between
sr8G
and SraB•
1'"
This correction resulted in a ma$ked ~provement
reproducibility
of the sr:e7/a~e6 ratio w1thou~
same time affecting
~e
the value of the mean.
of the
at 'the
Tha effect of
fract1ona~ion correction and the resulting improvement
of ~e
reproducibility
axe well illustrated by the analyses
of an olivine basalt from Kilauea,
Table A-l
Hawaii (Table A-l).
Olivine Basal~, Rllauea, Hawaii (R1292).
No.of
sr87/sr86 (srS'/sr86~
Date
rr
Bra6/SrBB
sr84/sr88 scans
6/1/60
0.7062
0.7068
0.1196
0.0070
138
8/3/60
9/3/60
1/25/61
2/8/61
0.1102
0.7072
0.1184
0.0063
84
0.7090
0.7040
0.7091
0.7069
0.7058
0.7061
0.1187
0.1200
0.1184
0.0066
84
0.0065
Average
007077
0.7066
.0.1190
0.0066
c;
1:. 0.0011
i; 0.0003
1: 0.0003
--
104
90
:to.OOOl
:t 0.0006
:t 0'. 0007 %0.0003
'.Corrected by adjusting sr86/sr8S to 0.1194 and the sr87/sr86
ratio by half this' amount.
(J
1: 0.0025
=21=
In this ser1SB of mgasu~amants
~O.0006
a reproducibi11tyaf
(0008%) haa bean achieved for the corxected
sr87/sr86 ratios.
This represents an improvement. by a
factog' of about four over the reproducibility
uncorrec~ed
ratios.
The importance
ation in the mass spectrometer
range of variation
rected
of the
of isotopic
fraction-
is illus'trat:ed by the
of the measured
values of the uncor-
sr87/S1:86 ratios as wall as the 8r86/8r88
sr84/sr88 ratios.
A precision
e~ror of O.l~ for the
8%,87/5X86 Z'atio can be achieved
effects
of isotopic
and the
only by removing
fractionation
the
in the mass spectro-
meter.
The accuracy of ~e
periodic
analyses of a
m9asurements was monitared
by
srco3 standard (Eimer and Amend,
lot 492327) for which isotopic analyses ~ave been reported
by Hegzog et ale (1953) as well as Aldrich
The average of elgh1: analyse~
performed
G~
during
of this invest.igation is in excellent. agreemsnt
earlier analyses
'the course
with
(Table A-2) as well as the original
measuremen~8 repotted
tium.
ale (1953).
by Nier (1938)
for me~al11c st.ron-
Table A~2 Isotopic Composi~!on of Strontium in Strontium
Reagants
AnalYBt:
N1ero 1938,
p. 277
0.712
~O.007
0.1194
:to.OO12
Aldr1ch et al.~l) 0.711
1953, p.458
~ 0.0004
Herzogat al.,
0.1195
0.0068
.:t. 0.00014
0.0067
Z 0.0003
:t 0.0005
0.1196
0.0070
0.712
1953, p.462
This work(2)
0.7119
:t
0.7120
0.1195
0.0066
0.0006 :t 0.0003
:t 0.0002
Z 0.0001
0Corrected by adjusting sr86/Sg88 to 0.1194 and the
sr87/8:-86 &'81:10 by half this smouni:.
(1) Average of
s1:st analyses,
(2) Average of eight
analyses.
The c~nelstency of our results for t:he srC03 standard
with those previously reported 1s an indication of the
reliability
of the analyses of the isotopic composition
of strontium. in basalts.
correc1:ed
sr87/s1:86
ratios
The reproducibility
achieved
in
of the
i:h1s case is 1:.0.0009
(0013%) •
On the basis of 1:1118 evidence single tosasurementsof
the sr87/sz86
ratio, corrected for isotopic fractionation,
of good ~all~y
:t
0.001 (0.14").
BEe
assumed to bave'a reproducibility
An analysis
is
judged 'to be of good
of
~ality if it is basad on 80
O~
more consecutive
scans
recorded at. pressures of less tb&n 2 :t 10-6 romof Hg
and if it is not otherwise
affected by instrumen1:al
diff1c\11ties.
Concentrations of rUb1ditun and s~gontium we~e determined by means of isotope dilution using spikes enriched
in 1£087and fh:.86, respectively.
were calibrated
by triplicate
against shelf solutions
The spike
isotope dilution
con~a1n1n9
analyses
known amounts of
rubidium and strontium of nozmal isotopic
The isotopic
solutions
composition.
cOO'lpoa1t:1onsof i:ha spikes ware confirmed
by separate trip11cai:e analyses
(Faure, 1961).
Four
blank. analyses for rubidium and stront:ium ware made in
~he c~'rse of this investigation
ination
corrections
were applied to all
(ab
0'. o 674/Agr..s. , 81:
analyses.
rUbid1um and strontium
cate analyseso
=
and appropriate
contam-
= O.250~.9r.s:)
The reproducibility
analyses was dete:m1ned
The results indicate
by tripli-
a reproducibility
of :t ~ for both rubidium and stront1UiU. analyses
m,
;1>
lS ppm and Sr '7 150 ppm. (Faure.
of 'the
1961).
when
Analvtical ~a~9~
The results of tl13 isotopic analyses of strontium
in basalts together with 'their concentrations
and strcnt:ium. are sho'\1nin Tsble ,ACl3.
brackets
of rubidium
The figures
in
after the measured value of the sr87/srS6 ratio
indicates the number of independent analyses perfc~ed
Averages of 'the ratios of st:rontium
for that speciman.
isotopes were calculated
for each local! ty from which
The sr87/sr86
more tha\nona speciman was analY2ad.
ratios
,,;ere weighted i.n the average by "the total
number
of specimens analyzad whereas the averages for the
6r86/sr88 and sr84/sr88 ratios
\t;ere calculated
total number of analyses performedo
olivine
Rb/Sr
basalts
=
found to contain
Rb/sr
=
of rubidium and strontium in five
average Rb
O.044t 0.018.
Rb
=
O.060Z 0.024.
All errors are the
mean.
standard deviations of.~a
The concentrations
=
17t.6 ppm, Sr
=
Rb c 6.9
ppm,
Sr
390 -r. SS ppm,
The six tholeei't1c basali:s ware
30'Z 7 ppm, Sr
One eclogit.e
=
504 :t.167 ppm and
a kimberlite
fZ'OID
pipe in S. nfrica was analyzed in duplicate.
are:
from the
I:
149 ppm, RbISr
=
The results
0.046.
Rb/Sr ratio of the eclogite is identical ~o ~at
olivine basal'ts.
The
in the
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"-
THE ISOTOPIC
COr~OSITION
OF 'S~ONTIm~
IN THE
SOURCE REGIONS OF BASALT MAGMA.
~~e
sz87isx86 ratios of basalts from different con-
t1nantal and oceanic.localities
vary between the limits
0.7047 (R2002, ~~ui Island) and 0.7101 (R4159, Iceland).
The eleven oceanic basalts average s~87/sr86
=
0.7072
t 0.0003 whereas the four~:~n continental basal~s have
a mean of O.7082 !:0.0003.
'!'he difference
between the
sr87 of continental and oceanic
abundances of
baaal~s is
no~ consistent and 1s probably not significant •. The
combined average sr87/sr86 ratio for all oceanic and
continental
variai:ion
basal ~s 1s
o. 7078 t. 0.0002
o£'+ 0.002 'and -0.003.
demonstrate
bomogeneity
wi ~h the 1im!ts of
The results
'therefore
of the source material ofbasal~
magma with respect ~o ~e sr87/sz86 ratio.
'!'his homogeneity could be 'the reeul1: of fortuitous
combinations
of the variable!?! ao' b, and to in a multi-
p11cl~y'o~ source materials
dence that
80
1tcould be taken as evi-
and 'to a.re constants
of basal1: magma. The latter
11: implies
or
for all source regions
interpretation
'that the small differences
ratios of basalts
from different
is preferrable.
in 'the sr87/sr86
localities
are caused by
corresponding
regions.
differences
in ~he Rb/Sr ratios of the source
The absolute values of the RbISr ratios calculated
for the sou~ce material of basalt magma depend on the selec~ion of values for ao and ~o in e~at1on (1).
The value of the init1~1 sr87/sr86 ratio (&0) and the
time of the differentiation
dete~ned
of the earth (to) have been
from analyses of meteorites. Direct measurements
of this ratio cannot be made because crustal roclcs formed
at that time have apparently not been pzeservad.
of meteorites
The use
to detexmine "~alues of ao and to for ~he
source regions of basalt magma can be justified by analogy
with the results for lead isotopes.
patte~son and his assoc~
ates showed that the abundances of lead isotopes in d1fferen~ stony meteori~es
at t
= 4.SS~O.07
preserved
Hanbury
and in Recen~ crustal rocks converge
billion
ye~rs t:o the primordial
abundances
in the tro11its phase of t.he iZ"on meteorite
(Patterson~ 1956).
The uranium"and
thorium contents
of this me~eor.tte are so low that the abundances of the
lead isotopes have remained virt.~.ally unchanged since 'toSimilarly, ''the value of 'the in! t1al sr87/sr86 ratio can be
determined directly from isotopic "analyses of strontium in
!a)-poor stony me1:eorites such as 'the achondrite
Pasamonte.
~2asurements of the sr87/sr86
ratio for this meteorite
have been ~eported by P2KZog a~d Pinson (1956), Schumacher
(1956), and Gast (1960a).
GastOs value of 0.7004+ 0.002
is based on triplicate analyses on two mass spectrometers
and is probably the most precise deta~ination.
of
0.002 is he~e considered tone the uncertainty
value as an estima~e of the true value of ~O.
that
The e~ror
ao :: O.7004:tO.002 and to :: 4.55TO.07
of Gastes
Assuming
x 109 years,
equa~ion (1) can be solved for (1Rb87/sr86) which is then
transf01~d
to ~e
weight-ratio of Rb/sr.
Using th~ae values for ao and to ~ha va~iation of the
srS7/sr86 ratio in basalt from"different localities 1nd1cates a range of values of the RbISr ratio in the source
material of basalt magma from 0.022 to 0.051.
Rb/sr zat10 is 0.039.
The average
A comparison of the calculated
values of. the Rb/Sr ratios of the source material
Rb/Sr ratios in basalts indicates
d~let1on
material.
of
Sg)
an enrichment
with 'the
of Rb (or
of the basalt magma relative to the source
The only exception to ~h1s are ~he basalts from
Hawaii Island whose Rb/Sr ratio is 1den~ical to that calcula~ed for ~he1r source regions.
'lhe average of 'the sr87/srSG
from HaltJa1i Island
ratios of four basalt.s
is O.7069;t 0.0003 whereas the basalt
from the neighbo~1n9 island of Maui has a value of 0.7047
i 0.001. This di£ference~
if real, can be interp~e~ed as
evidence that basalt magma was derived from two separate
source regions having different
Rblsr
ratios.
If the .con....
centration of alkali elements decreases with depth in the
source regions, differences
of srB7/sr86 ratios of basalts
could also be 1nterp:certed in ~erms of depth of the" source
material.
A comparison of the calculated. values of ~he Rb/sr
ra~ios of the source regions of basalt magma with the
Rb/Sr ra1:1os of different
types of igneous
rocks may serve
to identify tl1.enature of the source matexial.
tiona~f
Concentra-
rubidium and strontium in different types of
igneous and .eedimen~ary rocks wers compiled from the
literature
(Table A-4).
The calculated
averags Rb/Sr
ra~io of the source regions of basalt magma is 0.039 and
thUB
lies in the range of basalt, eclogite, and pyroxenite.
No reliable data exist for per1dot1~es •. ~ither
nor tile achondrites
materials
which have been analyzed
from which to derive basalt magma.
evidence preeen~ed here the conclusion
chondrites
are suitable
Based on the
is justified that
~he source material of basalt magma has an average Rb/Sr
-40-
ratio which
iUOSt
closely rss2rnbles those observed in ult~a-
basic igneou.s rocks and eclogite.
The analytical results and tlleig interpre~ation
sh~Jn in Figure A-i.
the
coordina~es ao
years.
Differences
The initial
=
point
are
is assumed to have
to == 4.5S:t 0.07 x 109
O.700~:t 0.002,
in the 8:&-87/sr86
ratios
of basalts
f~om different localities are a~tributed to corresponding
.differences
in the .Rb/Sr ratios of ~a
basalt magma.
The.basalt from Iceland
J:l1ghes'tvalue of the
development
source regions of
sr87/sgS6 ratio.
(R4159) has the
'!'hes'tront1um
line of its source material,'therefore
give an upper limit of the sr87/Sr86
regions t;hroughout geologic
for all source
time •. '!1l16 limiting upper
value will be used in comparisons
ratios of 1n~rus1ve
may
wi~
initial
srS7/sr86
xocks of unknown origin to determine
their possible derivatton from the source reglons of basalt
magma•. The slope of this strontium
be dei:erm1ned independently
development line
be measuring
the initial
sr87/sr86 ratios of Precambrianbaaic intrusives.
can
-41-
CD
co'"
U)
,,-'
CO&..
U)
0
,....
en
0
,....
co
,....
U)
0
,....
0
0
,....
0
0
0
0
0
,...
~
,."
Q
CD ~
en Cl)- ,."
V
lO
rt)
C\I
0
,....
0
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0
,....
0
d
0
0
0
I':
0
I':
0
0
0
,....
0
V
~-=lt)
N
~
<X
f/)
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m
LL
0
en
z
0
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0::
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0(1)
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=~W
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l=-Z
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ccj
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0: Z <tLlJ
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t!
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IOCDt-COC»O
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en 0
z
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V 0
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t:
0 Z
en
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!!!~
o )(
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,.... lO
o V
..
o
CD"'i:"
COen
n
rt)
-
alCD
OJ'"
en
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CO'"
0
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LaJ
:e
I-
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cooo
)(
<X
0::
-I
-I
en
UJ
:I:
I-
THE tSOTOPIC CO~~OSXTION OF STRO~U~
IN
Tim
CONTXNE~~~
CRUSTo
The objective is to show that the average
sr87/sr86
ratio of rocks in the upper regions of the continental
crust
is measurably higher than that of the source regions
of basalt magma.
To date only a small number o~ isotopic
analyses of strontium in crustal rocks have been reported.
Gast (1960a) analyzed ~en granitic roclts ranging in age
from 200 to more ~han 2650 mdllion years and found
ratios from 0.720 ~o 1.003, averaging 0.830.
sr87/sr86
Schreiner
(1958) reported va~ues ranging from 0.859 to 1.811 for
. the red granite
from the Busbveld Compls)t.
On t:he other
hand paleozoic limestones are known to have sr87/sr86
ratios close to 0.712 as does ocean water (Gast, 1960a).
It: is clear- that existing
the composition of crustal
data are not adequate 'to define
strontium but serve merely to
demonstrate the extreme variations
which exist.
range .of values 1s large because the crust
The
is composed of
_a great. variet.y of rock types of diffexosnt ages whose
Rb/Sr ratios vary th%ough several orders of magnitude.
In spit.e of this inhomogeneit.ymeaningful average values
can probably be obtained by analyzing the strontium in
those geological environments which a~e composed of or
contain weathering products of a variety of crustal rocks.
Such environments are geosynclinal sediments, metamorphic
rocks, parsgneisses,
glacial till, river water and ocean
water.
Isotopic analyses of s~ro~t1um in such rock types
are not ~'et available.
It is therefore necessary to
estimate the sr87/sr86 r~tio in the crust on the basis
of ~he average Rb/Sr and probable
crust..
age of the continental
Such an estimate will sho'~ that it is reasonable
to expect that the average s~S7/srS6ratio of a mass of
sialic rocks, which mdgh~ becama granitized during an
orogeny, is significantly higher than that of ~he source
regions of basalt magma.
The actual value of the initial
ratio of an igneous rock of crustal derivation
of course, on the geological history of ~e
~e
depends,
material.
average sze7/sr~6 ~atio of a,volume of geosynclinal
sediments, for 1ns~ance,w111
depend on ~e
proPortions
of volcanic rocks and limestone on the one hand and
de~rital sediments derived from wea~ber1n9 of ancient
continental rocks on ~e other.
An extensive survey of the geochamical
was undertaken
literature
in order to obtain the best estimate of
-44-
-the RbISr
ra'tios in different
continental crust.
of a precision
types of rocks and in the
Analyses were selected on the basis
error
of better
than
t:. 15%.
The analyses
were weighted in the average for each rock type
by the
total number of spec~menB rep~esented by each analysis
(Table A-4).
Table A-4
Concentrations of Rubidium and Strontium in
Igneous and Sedimentary 2ockso
Rock Type
Granite
Rb~~
196 «290)
1,4,5,6,7,8
Granodiorite
Syenite
Diorite andesite
Gabbro basalt
Olivine basalt
Eclogite
Anorthosite
pyroxenite
Chondrites
Shale
Limestone
Sandstone
Deep sea clay
1,2,3,7,9
122 (9) 4,8"
440 (85)
136 (14)
4,5,10,11
88 (21) 4,5,8
32 (331) 1,4,5,
7,11,12,13
18 (11) 7,11
6.9 (1) 11
0.6 (1) 11
0.5 (1) 11
3~17 (12)
156 (2) 10,11
0..
87
500 (13)
0.18
0.07
13,15,16"; 17,18
Achondri'tes
Sr 'Ppm
197" '(245)
0.37 (6)
13,15,17,18
149 (29) 3;5,19
5 (7) 5
60 (4) 5
110 (8) 5
3
3
440 (612)
0.28
2,3,7,9,.11
440 (11) 7,11
149 (1) 11
280 (2) 11,13
49 (1) 11
10.6 (2)
16,17,18
92.'1 (1) 17
300 (69)
3
610 (160) 3,19
20 ( ) 3
720 . (98)
0.04
OoOS
0.002
0.01
0.30
0.004
0.50
0.008
3
0.15
3,20,21,22
ooze
10 (6) 5
Number of
specimens ..
Globdgerina
( I)
2
Index to authors.
800 (3)
22
0.012
-45=
120 Fairbairn at al., 1953
13G Cabell and Smales, 1957
14. Pinson et al., 1953
1.
2.
3.
4.
Ahrens e~ al., 1952
Turekian, 1955
Turek1an and Kulp, 1956
Taylor et al., 1956
S. HOrstman, 1957
6. Sazhina, 1958
7. Gast, 1960a
8.
15. Gaat, 1960b
and lQ1i te:nrov, 1958
Dem!n
9. Katchenkov
&
I'legontova,
1958
10. Wager and Mi~chell,1953
c.
16, Herzog and Pinson. 1956
17. Schumacher, 1956
18. Webs~er et al., 1957
19. Heide and Christ. 1953
20 ..Clarke, 1924
21. Hevesy et al., 1934
22. Goldberg et: al., 1958
11. This work
Values from Table A-4 ware used to es~imate ~e
con-
centrat10ns of rubidium and strontium in the crust. as
defined in PoldervaartOs model (Poldervaart:,
results
1955).
The
are shownin Table A-5.
Table A-S
Concentrations of Rubidium and Strontium in
the Crust as Defined by Poldervaart,°s Mod~l.
Geoloqical
Environment
To~al crust
above Moho
74
441
Rb/Sr
0.17
Continental
crust only
87
442
0.20
Igneous rocks in continental shields
90
443
0.20
Sediments on continental
shields
88
229
0.39
sediments in yeung folded belts
Sediments in sUb-oceanic regions
Deep seased1ments
100
352
0.28
114
388
0.29
5S
660
0.08
It]) J)"Pm
Sr ppm
The Rb/Sr ratio of the continental crus~ is estimated
to be 0.20.
This includes
a laye7; of basalt: which is
assumed to exist at the bottom of the continental
Because we are primarily
masses.
concerned with ~be sialic portion
of the continental
is arbitrarily
crust an average Rb/Sr ratio of 0.25
accepted as moat ~epresentative
region .. This value is approximately
for that
'that of gra.nodiorites
shown in Table A-4•
.The sr87/sr86 ratio of a hypothetical geosynclinal
assemblage can be eat1ma~ed on ~e
sented in Tables.A.;.4 and A-S.
volcanic and sedimentary
basis of the data pre-
Such an estimate
recks of PoldervaartDs
for the
young
foided belt is shown in '1'ableA-6.
Table ~-6
the
Est1mat~ of
sr87/sr86 Ratio in a Hypothetical
Geosynclinal
Assemblage.
Sr x wt:."
Roclt 'lyJ:)e
Wt:." Sr D.Pm
100
ar87/sra6
S%%
44~3 .,. 0.733(1)
20
156
3
610
134
38.1
i
500
.25
Andesi'te
6.
500
Rhyolite.
2
197
Shale
52
13
.22
Graywacke
Sandstone
Limes~one
300
S~
100
0.324
0.733
0.712
. 0.271
30
7.1
8.5
0.708
0.708
0.050
0.060
4
1.1
0.708
0.008
0.9
352ppm
Total
x
87/86
.
0.007
0.720
(1) Pure shale and sandstone derived from weathering 'of
granodiorite 2 billion years in
(sr87/sr86)oz 0.70S.
The average ~r87/sr86
0.720 and 11:8 ftb/sr
8g8,
Rb/Sr
ratio for this assemblage
ratio
1s 0.28.
If
~a
= 0.29,
migh1: be
average age of
the continen~al crus~ is 2 billlo~ years and 1~s initial
sr87/sr:86 rat:10at ~at time was 0.704,
it would now have
-47=
an aver~ge
sr87/sr86 ratio of
0.725 assumdng its Rb/sr
ratio 0.25 as auggest;ed above.
~neee estimates ~~re confi~ad
by tho isotopic analyses
of strontium in two composites of Paleozoic
shale.
One of
these ccmpos1ts8 is from 'the Appalachian
l?rovince, the other
one is
The average
from the west coa~t (Table A-7).
srB7/sr86
zoatio 1s 0.7215 which is very close 1:0 the value predicted
for ~ geosynclinal
Table A-7
assemblage.
These shale composites
Isotopic Composition of Strontium in Ccmpos!~es
of Paleozoic Shale.
Sample
Ro. of
87/86
Number
Locality
-R4184
East coast: 0.7204
0.7204
0.1194
0.0064
44
R4185
tlest Coast
0.7232
0.7226
0.1192
0.0066
90
0.7218
0.7215
0.1193
0.0065
Average shale
(S7/86~orX' 86/88
84/88
contain calcite and probably same volcanic material.
scans.
They
therefore resemble 'more closely the geosynclinal assemblage
than a "pure" shale.
Based ontbe
evidence presented above ~be assumption
is just1f1ed<tha~
the RbISr ratio of the upper regions of
the co~1:1nen~al crue't 1s approximately
sr8'/sr86
is of the
ox:aer of
0.25 and that: the
O.72S:tO.OOS.
For age ae'tem1nation purposes by the Rb-Sr method it
-49is customary to assume an initial sr87/sr86 ratio of 0.712
0
This value is basad on analyses of the isotopic composition
of strontium in sea water and SrCO) reagents.
meaningful
It gives
ages only when the ~aterial is strongly enriched
in radiogenic sr87 so that the e~act value of tbe initial
abundance
of sr87 1s not importan~.
An
average crustal
sr87/srB6 ratio of 00712 implies tl1at the continental
cruet is composed predominantly
young acid volcanic rocks.
found 'that •
0
e.
of basalt or of relatively
Green and POldervaart
(1958, p.l0S)
'the geochemistry of Na and K 1s incompat11"Jle
with a theory of evolution of continents
by weathering
and
sedimentation of basaltic source rocks.
On the one hand
there 1s too much sediment, on the o1:her there .is net
enough Na and
1(
in sea-water".
Moreover, the age of the
.con~1nen~al masses is known to be of the order of 2 billion
years or more
0
An
average sr87/sr86 ratio
of O. 712 therefore
does not seem compatible with 'the chemical compositon of
the sialic
crust and1ts
abundance of sr87 in
causes
1.
probable 8geo
The apparent low
sea water maybe the resuli: of several
&
Recent and Tertiary volcanism in ~e circum-ocean1c
belts and in the oceans makes -a major contribution
to the total amount of strontium in solution 1n the
oceans. This volcanic st.rontium was developed in 'the
Rb-poor environment of the source regions of basalt
magma.
2.
Orogenic belts
in which young volcanic
rocks predom-
inate fo~ the major topographic features actively
undergoing arosion. An impor~ant groportion of
sedlm9n~s introduced into the oceans therefore has
low sr87/sr86 rat1oso
.
3.
4.
~mestones go rapidly in~o solution thus recycling
oceanic at%ontiwuo
Rubidium is concantrated in clay minerals and micas
of potassium.
These minerals are
by replacement
deposited in sed1menta~y baains and may prevent
accumulated radiogenic srB' from en~ering ~e oceans.
All evidence ar~'\a11ableat the praaen't time favours
the conclusion ~at
rubidium is concentrated in the sialic
upper regions of the continental
crust and that the average
value of i~e Rb/Sr ratio is sufficiently high
a measurable enrichment of the sialic
particillaJ: value of 'the.average
,
crust
to
in
result in
5r87•
1'he
sr87/sr86 ratio of a
volume of crustal rocks depends on 1~s geologic histo~
and the Bb/sr ratios
:1s reasonable
of its
component.rock 'types.
t:o expect 1:ha~ t.he! init.ial
11:
r:atio .of an
19neou~ rock of crustal
deJ."iva~ion is higher
than 'that of
a rock which originated
in the source regions of basalt
magma.
GeoloQ1cal Applications.
'the objectives
geological
materials
of
the st:udy of
sr87/Sr86 ra.tios in
can be sta~ed as follows.
~501.
To (~~t1nguish'i9neous
rocks formed by re-melt1ng
croat from 'those originating from the
source zeg10ns of basalt magma' in the upper mantle
OIl:' 'the base of the crust.
of the sialic
2.
To relate diverse products of magmatic d1fferen~1a-
'tlon to a comm.on source.
3.
To obtain information abou1:the chemcsl compos! t10n
of ~e
source regions of basalt magma.
The use of the initial sr81/sr86 ratio of igneous
rocks as a criterion
to determine
'the origin
ma~e&"1al
is 111us~J:ated in Figure A-2.
development line for ~e
:1.8 drawn
The strontium
source regions of basalt magma
from the initial point., based on met:eor1t1c
.data, to the upper limit of, variation of the
ra1:10 in basalts.
fore represents
there-
the maximum value of the sr87/sr86 ratio
It is implied that
regions
sr67/sr86
This line, 1f drawn correctly,
in source reglons of basalt
Ume.
of the
magma throughout
the
has remained constant
tion may need modification
RbIs!:' ratio
with
t~.
geologic
of ~e source
This
assump-
but serves as a firs~
approximation.
The most representat1 ve value of the szS7/8",86
ratio of the sialic crust at ~he pr,sent time is assumed
,
,
'to be O.72S:t 0.005 with an average' Rb/Sr ratio
as indicat.ed by 'the slope of the dashed
line in
of 0.25
.. -5I-
t-an
eno
C\ltt)
00
00
::>0
0:.
00
U)
COL-
en
.............
coL-
en
0
~
I'0
~an
do
+-
....JC\I
«I'-
0
C\I
I'-
0 eno
d
0
tt)
to-
~ + I
Oct CD
-en 0
I':ct I'om d
0
0
t-
d
U)
a::
ct
I&J
>-
C\I
lL
o
LLI
t-
U)
o:
o
z
z
o
o
....J
....J
:I:
o
ct
m
tt)
z
FiguzosA-2.
If tbe in! 1;1al 5r87/6r86 ratio
of an intrusi va
on or below the strontilhu
or volcanic
igneous rock falls
development
line of the source regions of basalt magma,
a sub-crustal
origin
is indicated
for 'that rock.
On the
other hand, if the initial ratio j~~s significantly above
'the s::87/sr86 ratio of 'the sub-c:ruetalsource
cZ'Ust:alorigin
is implied.
regions
a
The actual value. of the
lnl~1al 'sr87/sr86 ra~ioof such a rock will be a measure
of ~e
amoun~of young volcanic rocks of sUb-crustal
ozigin.mixed
with the sialic material.
In order to detexmine the initial srB7/srB6 ra~io
oian
igneouB rock it 1s nacessa:y to know l~s present
sr87/s~86 ra.tio, it:s Rb/sr ratio and its age.
.value of 'the initial
tiOD of the intrusive
The
ratio and the t.imeof crystallizaare also .glven by ...the ..coordina'tes
of 'the point of convergence
of the whole-rock
developmentlines.of several c~gma~1c
stront:1um
rock ~ypes hav-
_J
Lng different
Rb/sr ra~1os.
If ~e
rock was not re-heated
after its initial t~e of crystallization, the componen~
minerals
may also
ar87/sr86
ra1:10.
at10n of a vol~
be used to de1:ermine the 1n11:1al
In general
the products of d1fferent1-
of magma 1n1~lally all have the same
.. ,
'
.
srS7/sr:86 ratio
as t:heir l,areni; magma. Thereafter
fraction develops its own value of ~e
accordance with its
genceof
particular
the whole-~ock
number of associated
each
s~87/srS6 ratio in
Rb/Sr rai:10.
The conver-
strontium develoPment
lines of a
igneous .:rocks is therefore
evidence for a co-magmat1c relaf:lonship.
strong
The cQordiDates
of the point of convergence are the time of d1ffexent1at1~n
of the paren~. magmaand
at; 'that. 'time.
the
sr87/sr86
rati.o
of the magma
The magnitude of this value can tilen be
used 'to determ1ne
the origin of the magma as indicated
above.
This convergence
1:he differeni:iat1on
,
t.ast can be applied
of magma under d1fferen~
physical
..J
conaitions as indicated
-
~1ve1gneouB rocks.
.
by associated
volcanic
and 1n~ru-
It can also be used 'to de'termine the
r:e la't1onsb1ps of pegmat1tee,
~ etc.
to the study of
lamprophy~es, ccu:bon&tit:es ,
'to the igneous intrus:J.ves with which 'they may be
. associated.
A
co-magma'tic origin
be shown tha1:f~e1r strontium
1s indicated if 11; can
development; lines converge
to the same point as do ~bose of the associated
igneous
rocks.
In so far as basalt magmais faDled by partial
meli:ing of source material
in the upper mantle,
'the
abundance of sra7 in basalts ana other basic and ultrabasic igneous rocks from d1ffexent
geographic
localities
can be used to st.udy the homogenel ~y of :the uppex: mantle
...with :respect to its
RbISr ratio.
rai:1os of basic intrusives
crust at: different
The iniUal sr87/sr86
intruded into ~e sialic
times recoxd the abundanceof
" of the upper mantle throughout geolog1c t1meo
plot of these points va geologic ~
Prom a
independent
dence of the bis1:ory of differentiation
sra7
evi-
of tile upper
mantle" can be obtained.
Evidence of Sub-crustal Origin of ~e Intrusive
IqneouB Recks in 'the Monterec;s1an.HillB~ Quebec
The Monteregian -,hills" are a series of eight small
intrusives
of alkali-rich
igneous rocks e~endlng
from
Mont:eal{ Quebec, eastward across the St. Lawrence
lowlands
intrusives
for a distance
of about SO miles.
and their associated
,These
dikes and sills are cam-
posed of a grea~ variety of rocks ranging in compos!'tion
from basic essexite ~o 1ntexmedia~e
They" constitute
"province
collectively
which is believed
nepheline
syen1~e8.
a d1stinc~ pe~rog%apblc
to have formed as a result.
-55-
of crystal fractionation
multiple
injections
of a single parent magma. and
of the fractiona~icn products.
A
detail~ escript10n of ~e in~rusivesand a complete
bibliography
were given by Dresser and Denis, (1944,
p. '455) •.
These igneous rocks have intruded Precambrian crystalline rocks of ~e
leas,t 1000 million
foming
Grenville Province which are at.
years in age.
Muchof the material
the metamorphic rocks of 'this reglon probably
came. from older Precambrian
areas to 'the North, with
ages of 1700 'to 2600 million years.
ratio
The s~87/sr86
in 'the host rocks is theref(ore undoubtedly well
up in the range of values for ancient continental
crus~al
, reg10ns.
The age of the intrusives
is 122:t9m1l11ol1 years
-according 'to It-Ar age de te m1nat:ion 'on biotl~e f:rom
Brame Mount:a1n (Lowdon,
1960,
~.38).,
This
confizmed by the Geochronology Laboratory
(Ann. Progress
age has been
a1: M.I.T.
Repor1:, 1960, p. 283).
Iso~oplc composi~1ons of stront1um in four specimens of igneous rocks from the Monteregian hills and in
one sample of
calc! 1:e from
a
~arbona1:1 'te
at
Olea were .
-56dete~ned.
Concentrations of rUbidium and strontium
were measured in
dilution.
two
of the igneous rocks by isotope
The experimental data are sbown in '1'able~-8.
Discussion of EXPerimental RssultsA
The average value of ~he corrected
of the essexite,
sr87/sr86
ratio
the yamaskite and the 'tinguate is 0.7049.
'Ibis value is cons1dexablylower than tilat for 'the nordmark!1:0 which is
o. 7156.
However, when the st:ront1um
developmen1:lines, with their
error
envelopes are plO~1:ed
for 'the nordmarkite ana 'the yamas1d.1:a,an inursection
ob'tained at t
=
115:t 25 million years and
O.7047:t 0.001 (Figure A-3).
s'r87/sr86
is
•
Thie time is identical within.
experlmen'tal error to the age of the biotite from Brame
Moun~ain whlch was de1:exm1nedby ~e
It-Ax" me'tbod.
'lhe
'time at which the s~ront1um development lines intersect is
the z:efore,also the time a~ which 'the different rock types
were separated
from t:he parent magmaand :from each other
ane) began to accumulate radiogenic
w1ti\ their different
Rb/sr ratios.
s~ront1um in accordance
'fh1s is strong evidence
that the nordmal'1citeis a magmatic differentiate
of ~e
same parent magma which gave rise to the yamaskite and ~e
-57-
&nro
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I:
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rock types.
other
..
The only way in which the nordmarki te
could develop a sr87/sr86 ~a~io of 0.7156 in 115 million
years is to have had an initial
ratio
of 0.7047.
the n~rdma:r:kite magmabeen contaminated
Had
at the. time of
its intrusion with old crustal material having a sr87/sr86
ratio much greater.1:ban 0.7047.
intersection
with the yamasklte
It could not give an
at a time which is known
t;o be the age of these rocks from other evidencee
The sr87/sr86 ratio of tbe parent magma was
1:. 0.001.
Th~.s 1s sugpgis1ngly
low when compared to tbe
average sx87/sr86 gat10 fo: oceanic
basalts
which is 0.7078 + O.0~2
abundance
= 0.7047
and co~tlnental
(Table A-3) •. The low
~O.003
of the srB7/@r86 ratio indicates that the
source material
from which the magma was formed had a
very low RbISr J:at:io, even lower tilan the source material
for average basalts.
The Rb/sr ratio of the source mater-
1al 1s estimated by assumingan age of 'the earth of 4.5
billion-years
and an initial Sr87/sr86 ra1:10 of 0.7004
~ 0.002 (Gast, 1960a.).
~e
this way is 0.022:t 0.011.
only an ultrabas1c
RbISr ratio calculated
in
This value 1s so low tha~
rock could ~a11fy as a source for
the primary 'Monteregian hill
magma. If
the content
of
alkalis decreases downwar4 in the upper mantle, this
value would sU9ges~ tbat the source region for the magma
was at considerable
depth in t.he upper mantle.
The isotopic composition
of strontium in calcite
from Nb ore from a carbonat1~e
concentrated
at Oka,
Quebec, was determined for comparison with the strontium1n
the tgneous rocks of the Monteregian hills.
The average of two independent
8r87/sr86
=
0-.7062'.:t 0,.0005.
thecarbonatite
dei:enrdna't:Lons gave
The srB7/sr86 ratio
is therefore notmeasu:cably
from that: in the basic igneous rocks.
not inconsistent
with ~e
conclusion
different
The results
or1g1n
rocks.
This conclusion 1s si:rengthened by compar1son
&\
Sr87/81:86 ratio
of
(1960a) for Grenville
are
that the calcite
of the carbonatlt;e at Oka 1s of sub-crustal
and is related 'to the igneous
of
O. 709:t:O. 002 reported
limestone.
with
by Gast
An impure Grenville
11~8~one containing a small amount of mica would be
expected to have an even higher ratio.
Gast also gave
a value of O.713:tO.003 for an Ordov1c1an
Pel:ry County, Texas.
l1mes~one from
-61Conclusions.
The results of isotopic
2S basalts
fram oceanic
analyses
of strontium
in
and cont1nen~al localities
1ndi-
cate that the source regions of basalt magma in the upper
mantle are homogeneous
within narrow limits with respect
to the sr87/sr86 ratio.
ratios in basalts
~e.
average value of this ratio
is consisten~ with the conclusion
the source regions were initially
homogeneous
that
with .res-
pect 'to the abundanceof Sr87•. The differences
in the
sr87/sr86 ratios observed in Recent and Tertiary ba~alts
from different
geographic
have developed
in response
variations
localities
of the Rb/Sr ratio in the upper mantle
sr87/sr86 ratio
since
Assumingthat the
was O.7004:t 0.002 and t :: 4 5
0
x 10.'9 years, t:he Rb/Sr ratio
of the source .regions
of .basal't magmais calculated to be 0.039+ 0.012.
.
-0.017
value is in. the range of the RblSxrat10s observed
eclogit.e, olivine basalts
rocks.
to
~o lateral and/or vertical
the time the mantle solidified.
in! t1al
are believed
This
in
and cexta1n ultrabas1c igneous
.
The Rb/Sr ratio of the sialic po~t1on of the cont1nental crust is estimated
to be.O.2S
ical evidence presently available.
cantlyhigher
from the best geoehemThis value is signifi-
than that indicated. for the source .regions
of basalt magma. Ii: is t:herefore expected that the average
sr87/sr86 ratio of the sialic crust is measurably higher
than that of the. sub-crustal
Reasonable
estima~es
sources
of basalt
magma.
of the age of the sialic crust and
its initial sr87/sr86 ratio suggest a p%cbable present
.average value of 0.725:t0.005
Based on this evidence
for this ratio.
'the hypothesis 1s advanced
that the sr87/sr86 ratios of intrusive and volcanic
igneous rocks in the sialic crust at the ~1me of their
crystallization,
andgranitized
can be used to dis~inguish
sia11cmaterial
from differentiation
ducts of basal~ic magmaof sub-crustal
applic~i11~y
of the .initial
re-melted
origin.
pro-
'I'he
of this ~est depends on the actual value
ratio
of an igneous rock of possible
sialic derivation
and on the degree of certainty w1~h
which it can be distinguished from the sr87/sr86 ratio
of the sub-crustal
source regions of basalt.
The strontium'development
lines of co-magmatie
igneous rocks which are fractionation
products
of a
-63-
common parent magma converge
back\'1ardsin time.
The
to a point when plotted
coordinates. of 'this point: are
~he time of differentiation and the
the parent magmaat: that time.
relationships
between
lines.
It: 1s suggested that the
suites of diverse differentiation
products can be de~e~ned
vergence
sr87/sr86 ratio of
by testing for possible con-
of their whole-rock
strontium developmen~
Thls methodmay also be. used to determine the
relationships
of pegmat1tes,
phyres with associated
carbonatites
intrusive
The isotopic camposlt1ons
intrusive
igneous.rocks
and lampro-
igneous rocks.
of strontium
from the Monteregian
in several
hills,
..
.~uebec,
products
indicate
ti1at they.are
of a commo)lpa~ent
nated at considerable
the dlfferentiat:1.on
magma which prObably
origi-
depth below the base of the crust.
The abundance of sr87 in a sample of calc1~e from ~e
carbonatite
at Oka, Quebec, is not inconsistent
the conclusion
that it is directly
igneous rocks in 'the Mon~re91an
w1th
related to tbe
hills.
Acknowled~nts.
It is a pleasure to ackn~~ledge our deb~ to Professors
w.
H. Pinson and H. W. Fairbairn
who in many ways assisted
in the chemical processing of the samples and the mass
spec~romet:ry.
G. Faure received
financial assistance
from Imperial 011 L1m1t:edthrough an Impe%lal 011 Graduate
Research Fellowship.
The support. of the Division of
Research of the Atomic Ene~9Y C~ssion.1s
acknottlledged.
gratefully
References.
Ahrens, L.P., W.R. Pinson, and M.M. Rea~ns, Association
of rubidium and potassium and ~he1r abundance in
commonigneous rocks and meteorites,
Geochim. e~
Cosmoch1m. Acta, 2, 229-242, 1952.
Aldrich, L.T., L.P. Herzog, J.B. Dealt, and G.L. Davia,
Variations in s~ron~1um isotope abundances in
minerals, part I, mass spectrometric analysis of
mineral sources of strontium, Trans. ~.m. Geophys.
Union, 34, 457-460, 1953.
Cabell,
J.J. and A.A. Smales, The detexm1nat1on
°
of rubi-
dium and caesium in rocks, minerals and meteorites
~y neutron activation analysis, The Analyst, 82,
390-460,
1957.,
Clarke, P.W. and R.S. Wasbington, The composition of
the ear~ho8 crust, U.S. Geol. Survey, Prof. Paper
127, 1924.
Demin, A.M. and D.N. 1<h1'tarov, Geochemistry of X, Rb,
and Tl applied to problems ofpe~rology,
°Geokhimiya,
6, .570-581, 1958.
Dresser,
J.J\. and 'r.C. Denis, Geology of Quebec, Geologi-
cal Report 20, vol.
of Mines, Province
PairbairD,
2, Descriptive
Geology, Deparb!ent
of Quebec:, 1944.
H.W., L.H. Ahrens and L.G. Gorfinkle,
element content of Ontario diabase,
Cosmoc:b1m. Acta, 3, 34-46, 1953.
MinoX'
Geocblm. at
Fauxe, ,Gunter, The sr87/sr86 ratio in coni:lnental and
oceanic basalts and the origin of igneous rocks,
Ph.D. thesis, Dept. of Geology and Geophysics,
M.I.T., 1961.
Plynn, K.F. and L.E. Glendenin, Half-life and beta
spectrum of Rb87, Phys. Rev., 116, 744-748, 1959.
Gast, P.W.,,, Limitat.ions
mantle, J.Geophys.
on the composl1:1onof the upper
Research, 65, 1287-1297, 1960a.
-66-
Gast,
P.w.o Alkali ma'tals in stone meteorites,
et Cosmoch1m. Acta, 19, 1-5,. 19'60b.
Geochim.
Goldberg, BoD. and G.O.S. Arrhenius, Chemistry of Pac:1.fic
pelagic sediments, Gsocbim. et Cosmochim. Acta, 13,
153, 1958..
Green, Jack and AJ:1e Poldervaar~,
trends, ~och1m.
Petrochemical
fields
and
et'Cosmochim. Acta, 13, 87-122, 1958.
Heide, F. and W. Christ,
ZUr Geochemie
des Stront1ums
und
Bariums, Chemie der Brde, 16, 327-330, 1953.
Herzog, L.P., L.er. Aldrich, W.K. Holyk, P.S. Whiting and
L.R. Ahrens, Variations. in strontium isoi:o~ abundances in minerals,
paX'~II,
J:.ad1ogen1~8r87 in
biotite, feldspar and celestite, Trans. Am. Geopbys.
Union, 34, 461-470, 1953.
Herzog,L.f'. and W.H. Pinson, RbISr age, elemental and
isotopic abundance studies of stony meteorites. Am.
J. Sc~., 254, 555-566, 1956.
Herzog, ~.P., W.R. Pinson and R.P. Coxmier, Sed1men~ age
detem1na~1on by Bb/Sr analysis. of glauconite, Bull.
Am. Assoc. Petroleum. Geolog1s~8, 42, 717-733, 1958.
..
"
Hevesy, G.V. and K. Wt1:r:st.lin, Uber die
Stxon~lums,
z. Anorg,
Holmes, A., The origin
69, p.S50, 1932.
Hauflgke1t
des
Allgem. ahem., 216, p.312,1934.
of igneous
rocks,
Gaol. Magazine,
Horstman, B.L.,
The distribution
of lithium,
rubidium,
and caesium in igneous and sed1mentar:y rocks,
Geochim.et
Cosmochlm. Acta, 12, 1-28, 19S7~
Katchenkov, S.M. and' B.I.
P1egontova, Minor elements in
the basement rocks of eastern part of the Russian
plat.form, Geochemistxy,2,
p. 224, 1958.
Lowdon, J.A .. (ed.),
Age detexminaUons
by the Geological
survey of Canada, Report 1, Isotopic Ages, Paper
60-17, 1960.
PAGES (S) MISSING FROM ORIGINAL
webs'ter, KoR., J.W. Morgan and D.A. Smalea, Some recent
Itazowellanalytical work on geochronology,
Trans.
Am. Geophys. Union, 38, 543-545, 1957.
Wager, L.R. and R.L. Mitchell, Trace elements in a suite
of Hawaiian lavas, C-eochim.et Cosmochim.Acta, 3,
217-233, 1953.
-69-
Part II
-70-
Chapter 1
RATIO IN ROCKS
AND
THEIR GEOLOGIC SIGNIFICANCE •
.....
VARIATIONS
OF THE SR87/SR86
Introduction.
The element
strontium
has four stable isotopes,
sraa, Sr97 , sraG, and sr84•
namely:
One of these,
sr:87, is the daugh'ter product of the radioactive
of Rb87 and its
'abundancehas 'therefore increased throughThis :Lncrease 1n the abundance of Sr87
out geologic: time.
1s conveniently
decay
expressed
in terms of the
As will be shown later, the ratio
sr87/sr86 ratio.
sr87/sr86 at any
point in the earti1 increases in tima as a function of 'the
RblSrrat10 a~ thai: point.
mineral g:r:a1nsand
I'OC~
This is true not only for
specimens but also for large di v-
1s10n8 of the earth such as the continental
mantle.
>
'Both
these large-scale
crust and the
geological environments
have developed, throughout geologic 'time, characteristic
sr87/sg86 ra~ios"in accordance with their Rb/sr ratios.
A survey of 1:he geochemical 11i:erat:ure (Chap~er 2)
suggests ~at
the
RbISr ratio of the continental
approximately 0.25.
crust is
On 'the other hand, the isotopic
-71-
composition of strontium in basalts of sub-crustal
demands a ~/sr
(Chapter 6).
ratios
origin
ratio of about 0.04 for ~he upper mantle
Because of 'this difference
!t is expected that
developed significantly
in the Rb/Sr
the crust and the mantle have
different ave~a9a Sr81/sr86 ratios.
The act.~al value of ~h1s ratio in the crust is not
, knownwith certainty
age of ~e
at the present time.
If the average
con~1nents is 2 billion years, their Rb/Sr
ratio is 0.25, and the 1ni~ial
sr87/sr86 ratio is 0.7004
1: .002, the present value of the Sr87/sr86 ratio should
be 0.725.
Chapter 3.
This topic is discussed in more detail
in
On the other hand, .the average sr87/sr86 ratio
of 25 oceanic and continen~al basaltic rocks of sUb-crustal
origin
is 0.7078 ,(Chapter 6).
ment precis1on.of
Mass spectromatric
measure-
the sr87/sr86 ratio can be as low as
:to 0.001 for a single determination (Chapter 5) so t.ha~
the ,difference betwe;en crustal
strontium and man~le-
stro~Uum is clearly measurable.
This difference between man~le-s~rontiumand crustal
strontium has important geological
implicationsl
of magma formed by partial melting of ~e
A body
upper mantle
and injected into the crus~ contains strontium which was
developed in 'the low-~b mantl~ environment:.
of magmatic d1ffexentiat1on
of sub-crustal
~ll products
magma will
-72-
likewise contain mantle~strontium.
difference
Because of 'the
of the sr87/sr86 ratio in the crust, mantle-
strontiwnc:en be recognized and iden'tifled
as such.
srS7/sr:86 ra.tio of igneous rocks at the t1meof
The
their
c~'stal11zat1on is therefore a possible cr1terion for
crustal or sub-crustal
origin.
Thepurpose of this study is to ascertain the exact
value and the range of variation
in ~he sUb-crustal
magmatic
done by analyzing
origin
continental
localities.
sr87/sr86 ratio
source regions.
the strontium
sub-crustal
of ~he
in 2S basaltic
rocks of
from a la%ge number of oceanic
'rUbidium and ~trontlum
In addition
and
concentra~1ons
of
were determined for a,representa-
tlve number of basalts' in order to compare
ra'tios of the rocks to those calculated
regions.
This 'was
the Rb/Sr
for their source
Such comparisons are ~ne way in which 1nforma-
tion about the. processes of magmaformation can be
In add1~lon
gated:
several related topics were investl-
The age of an eclogite,
the origin and differentl"
atlon of magma in the Monteregian
study the variation
mantle
of the
'
hills and an attempt
to
sr87/sr86 ratio of the upper
1n the course of geologic
time by detexm1n1ng
'the
-73-
sr87/sr86 ratios in several Precambrian basic
initial
intrusives.
The value of the half life of Rb87 used throughout
is .T := 47I 1 x 109.years
'this thesis
(Flynn and Glendenin,
1959) •
Derivation of ~he Strontium
~velopment'Equation.
Russel and Allan
equations
f01:
isotopes.
(1955) derived completely
the variations
~ese
general
in the abundances of lead
equations were adapted to the Rb87decay
scheme by Gast (1960, p.1291).
In 'the toll~Jin9
the
a
strontium developmen~ equation .1s simplified into more
approximate but more easily useable fo~.
The d1s1n~e9ratlon of Rb87 to Sr87 is subject ~o
the law of nat.ural radioactive decays
_,\t
P ==
(1)
P09
where
P
Po
A
t
IQ
="
-..
-
number of parent a'tams at time t
number of paren~ atoms at time t
decay constant
time.
-
0
The number of radiogenic daughter atoms ""D is
given by
At
SUbstituting
appropriate chemical symbols for the
numbers of daughter
*sr87
(2)
-i).
:: P(e
and parent. atoms:
= Rb87(~t._l)
(3)
The total number of atoms of isotope
sr97 in a given
sample of matter is
Sr87
where sr\'
Therefore
= sr~l +
esrB7
(4)
1s the number of atoms of Sr87 at; t
the total number of atoms of
=
O.
sr87 in any 9~ven
system at any .t1~1s
Sr87
=
sr8~
+
Rb87
(jt
(5)
-1)
.l\bile the numberof Sr87 atoms increases as a function of
'time and the nu."Bberof Rb87 atoms in the system,
'S 86 -
f
or-atoms
remain unchanged. It 1s therefore pemiss1ble
to divide both sides of equa't1on (5)
sra, /sr86
.
the number
-
(sr87/s1'86) +
0
by sreG•
~b87 /sr86(e
At
-1)
(6)
-75m
Equation (6) is entirely
.
)
rigorous.
..
imation is introduced by ~xpanding e
A.+
The first
approx-
in a powsr series
and neglecting all but the first two te~s.
Ai
Since e
- 1+
-
.
2
A..t + M..u
2~
JA t.l~
••
3:
0
This approximation causes a maximum error of 3.4" when
t
8;
4.5 billion years.
the error lereduced
If t:he 'third tem
1s included,
to 0.07$.
ttherefoX'e,
~r87
~
_s_r8_7_ +
srS6
(7)
sr86g
It is convenient ~o transfo~ the a~omic ratio Rb87
srst;
into a Weight ratio:
87 • (Rb)
Rb
sr8a~.,._...... Sr
'-~~ ..
PhS7
"At.
~'e1gi~:t
\\It. 51." x A
At:ewt.RbxAS~
6
(8)
where
RbS7
,
A
1m
isotopic abundance of R))87 at the p:esent
time, expressed as a fraction of the total
number of rubidium
86
sr
A'
=
~~cms.
isotopic abundance of Sr86 in the sample of
strontium for which the sr87/sr86 ratio was
determined.
-76-
Substi'tut1ng (8) into (7)
_8....,r8_7~
_
8r86o
(!1l)
Ate~lt.Sr.A
x
Rb87
(9)
At. ~~t Rb. ASr86
Srwt
It
If k :=
(10)
The num{~;:ricalvalue of the factor k is calculated
. from the atomic weights
'the abundances
of rubidium and strontium and
of Rb87 and sr86 a~ 'the present ~1meo
Since the atomic wa1gb~ of strontium and the abundance
of srB6 depend on the aw~unt of radiogenic sr87 present,
~e
factor k is. not strictly a constant but should be
evaluated for 'each sample.
1.35% when the isotopic
The value of k increases
composition
~~ween ~he limits sr87/sr86
For "normal" strontium
by
of strontium varies
=
00712 to 0.850.
It
=
87. 710 :Ie 0.2785 - 2.8962.
85.557 x 0.0986 -
The strontium encountered here does not differ
greatly from "normal- strontium and 'thevalue for k
= 2.8962
will be used in all calculations
unless otherwise
stated.
The final form of the strontium developmen~ equation
-77-
CD
.CD ..
fn
'
CD
rt)
CD~
.......
r--:
(/)
0
CD
I'-
C\I
en
I'-
0
ci
~
0
0
0
0
I'-
0
0
0
~~.
0
~
--~~
":s'
.
0
(/)
en"
:is
a::
<t
lLJ
a:
>-
C\I
LL
0
(/)
Z
0
...J
...J
lIJ
:I:
....
LL
0
W
U)
~
W
lLI
.
....- ....
~
:I: 0:
....- ..
~ ,
(/)
0::
0
Z 0 ..0
0:
-.
CD
:E 0
....
~
LLI
0:: :I:
WCD
....
~U)
Q
O::CD"
C)I'-'
Z
-CD'"
~
LLCJ)
",
Z
lLJ
:E
-
I-
-
sr67
sr86t
Equation
a:t
~1;'8.!
8&:86
-+
x(~)
Srwt
0
A
(11)
t
a family of straight lines which
(11) describes
have a common origin at t
The slope of the lines
20896
= 0 when sz87/sr86 -
is 91ven by 2.p\6(:~)
tberefore a function of the RbISr ratio.
straight lines is.shown in Figure 1.1.
A
(sr87/srcS6)o.
A
a.nd is
system of such
The value of tbe
in1~ial sr87/sr86 ra~io is arbitrary on such a plot but
has a definite fixed value for strontium in our Bolar system.
The value of the initial sx87/sr86
of the differentiation
ratio at the time
of the earth has been detexmined
from analyses of meteorites.
Direct meaauremen'tB
of
this ratio cannot be made because crustal rocks formed at
that t:1ma-have apparently
not been preserved.
Before the isotopic composition
meteorite
can be identified
of terrestrial
strontium
as ~e
of strontium
primordial
in any
composi~ion
11: must be shown thatl
10
Different types ,of meteori~es ~are produced initially
from homogeneous pa~ent material and that ~hey have
existed as closed cheroical systems since that ~1me.
2.
That terrestrial stzont1um originated from the same
parent material and initially had the same abundance
of srB7 as the'meteorites.
Patterson and his associates demon~trated
that the
abundances of lead isotopes in different types of fGStecrites
and in the crust of the earth satisfy both conditions
(patterson, Goldberg
and Inghram
pa't'terson, Brown, Tilton
(1953), Patterson
and Inghram
(1955), pat~erBon, Tilton and Inghram
(1956) ).
The above authors
of lead isotopes in different
young crustal rocks fom
billion
(1953),
(1953), Patterson
(1955), Patterson
showed 'that 'the abundances
stony meteorites
an array converging
and in
at t
= 4.5
years to 'the primordial abundancespreserved in
the tro11ite phase of 'the iron meteorite Henbury. The
uranium and thorium contents
low that. the abundances
of this meteorite
are so
of the lead isotopes have remained
virtually ~nchanged.
By analogy \oJ1
tb lead the assumption is
terrss'tJ:lal strontium
composition
justified
-initially had 'the same isot.opic
as meteorite
stront1umo
The va.lue of the
primordial sr87/~r86 ratio can be found directly by
'that
-60analyzing
strontium
in P:b-poozostony meteori t.ea t'\1hich
have prese~ved their initial sr87/sr86 ratio,
from the point of convergence
be dete1~nsd
O~
it can
of the
development lines of strontium in several different
at:ony meteorites.
by
The first approach has been prefeX"red
several invest1ga~orB who have
r0ported sr87/sr86
,
.
values foz achondritic
meteorites
wl10ae ~b/Sr ratios are
less than 0.01 ~able 1.1).
~able 1.1
The Primordial sr87/Sr86 Ratio
Herzog and Pinson,
1956,
p. 560.
Schumacher,
p. 211.
1\chondr1te
(Sr87/srS6)0
Invsat1qator
1956,
Gast, 1960~ p.1290.
Average pasamonta
0 ..703
0.691
psaamonte
0.687
Pasamonte
0.7011.
0.7005
0.6995
pasamonte
0.7004,
It
II
V-:I:
0.0005
.1
O.7015 :t 0.002 Sioux Count~
Ie
O.7027!:. 0.002
Nuevo Laredo
Herzog and Pinson (1956) preferred a sr87/sr86 ratio
'of 0.703 for Pasamonte. This value is definitely
than tha~ quoted by Schumacher(1956).
higher
Gast (1960) re-
independent analyses perfo~ed
on t~o mass spsctromaterso
His avegoage value is 0.70041: 0.0005.
This result
a.grees with that of Herzog and Pinson
(1956) within the
limits of error stated by them.
therefore
Schumacheros analysis is
now considered to be in error.
GastOs values for tIle
srS1/sr85 ~at1os in
Siou~t
County and Nuevo Laredo are 0.7015 and 0.7027, respectively.
The error ofzO.002
assigned to these analyses was not
fur~her explained by Gast and is ass\tm2d to be a limit. of
uncertaini:y.
It is unfortunate that no attempt has as yet been
made to determine
the initial sr87/sr86
point of convergence
ratio from the
of the strontium development
of several stony meteorites.
lines
This would give an independent
check of the value obtained by ~irect analysis of Rb-poor
achondrites.
Forest City and Homestead
are the only chon-
drites for which sr87/sr86 ratios as well as Rb/sr ratios
have been determined.
meteorites
The analytical
are shown in Table 1.2.
data for
these tt~O
Initial sr87/sr86
ratios were calcula~ed assuming that ~e
age of the earth
1s 4.5 x 109 years and using a decay constan~ for Rb87 of
47 t 1 x 109 years
(Flynn and Glandenin,
1959).
Table 1.2 Initial srB7/sr86 Ratio in Chondritic
Rb/Sr
Meteorite
Forest. City
Me~eori~es.
o. 755tO
..003~
O.30tO.03S~~ O.69B!O.007
Homestead
tJ Gust"
0* Table
~~*
1960.
2.1, Chaptsz 2
Herzog and Pinson, 1956.
It 1s evident. from 'the data in Table 1.2 that publisl1~d
values of the sr87/srg6 ~1d the RbISr ratios in stony meteo~~
ites do not have sufficient precision
~o calculate
values of the initial sx87/sr86 ratio.
zeliable
The beat estimate
of this ratio must therefore come from direct analyses of
Rb-pooX"stony meteor! ~es such as Pasamonte, Nuevo Laredo
and Sioux County.
GaatOs value of O.7004~O.002 for pasamonte
is here
accepted as the best estimate of the initial terrestrial
sr87/sr86 ratio not only because it is the most precise
measurement but also because it has the lO"Jesi: value of the
srB7/Sr86 ratio of the three achondrites.
of PaBamon~e is ~O.OOS
(Schumacher,
The Rb/Sr ra~io
1956) and its Sr87/sr86
ratio has therefore remained virtually
unchanged wi~h t1m2.
On the other hand, ~he ?~/s~ ratios of Nuevo Lazedo and
Siou)t Coun~y are not' ltnot~£'afaXt
is
.:;he2:efoE"s possible
thC1'i:
the slightly higl1er s~B7/Bx86 ra~!os in these ~wo ~~~eoritea
are caused by smmll inc~eases of the Sr87/S~86 ratio with
time.
Nevertheless.
a litnii: of uncertainty
of
t.. 0.002
will be accepted with the measured srS7/sr86 ratio of
paeamonte in order to include, at least partly, the other
.two achondriteso
t
An initial srS7/s&86 ratio of 007004
0.002 will be used in all calculations throughout ~his
thesis.
As early as 1932 Holmes proposed that the differences
in the ab\.\ndanceof
ca41
could be used to distinguish
between granites formed by refusion of granitic pa~ent
material and granites which are differentiation
of basaltic magma.
tion,
now disproved,
products
This suggestion was based on th0 assump~
that: K41 decays by
13-
emission to
ca41•
In the course of the thirty years sin~e this remarkable
scheme was proposed radioactive
widely used for age date~nation
elements have become
purposes.
The abundances
of daughter isotopes, however, have not been applied
extensively to derive the geological info~ation
reformulai:e
Holmea ° s idea in tenas
visua-
of the abundances
of
the radiogen1~ isotope sr87
0
~ne objactivea in ~he study of
sr87/sr86 ~atios in
geological materials are conveniently
listed as follcws~
1.
To distinguish igneous rocks of crus~al o~i9in from
tllose of sub-crustal origino
2.
To relate diverse products
of mmgmat1c d1fferentia~
tion to a common parent.
3.
To
obtain
1nfo~atj ..on about tIle chemical composition
of the magmatic source ICGgions in the upper mantlell
In the following pages these three topics will be discussea
in soma detail.
The Oriqin of Grani~1c Igneous Rocks.
the present
time is O.7078-+0.002 - 0.003 (Chapter 6).
On tbe other hand, there is evidence
this ratio in ~e
O.72S:t .005.
(Chapter 3) that
continental crust 1s approximately
Ac:hondritic lOOt.eozites
indicate
that
the
srS7/sr86 ra~104.5 billion years ago was
Oo7004io.002.
These facta are c~~ined
Ord0%
in Figure 1.2 in
to illus-
trate the changes in the sr87/sr86 ratio in the crust and
-85-
C\J",
&0
00-
0
(0
cot..
U)
co'"'""
U)
0
0
v
r--ci
",
r--0
0
~~~
+ 1
e:!
+1
co
en
C\J
0
C\J
.....
r---
ci
0
0
&0
r---
r--0
r---
0
\
\
e:!
m
ci
..
U)
t-
::::>
CI)
ct
0:
0
(,!)
W
:J:
1&.1
to-
\
Z
0
\
Z
~
en
~
(f)
e:!
""" ,
\.
t-
":
0
\
t-
0
0
,,
0::
«
uJ
C\J
1&.1
I-
LL
Q:
0
z
0
:I:
0
(f)
0
Z
ex
Q
W
..J
t-
Z
0:
::e
0 t",
« «
(0 ..
cou)
'
.....
cot..
.(f)
:E
....
tZ
LL
v
LLJ
:J:
o:
:::> 0
(!)
«
m
W
a..
a..
N
W
..J
..J
Z
0:
W
::::>
.
>-
It)
~
in the upper mantls thzoughou~ geologic time
o
~fuan a volume of 9~anitic magma is produced as a
product of magmatic d1fforent1a~ion
of basalt magma of
sub-crustal origin, ita initial s~87/sr86 ratio at time
t will be 0.709, or less.
magma is produced by fusion
On the other hand, if gran1~ic
O~
grani~ization of average
crustal rocks, ita sr87/sr86 ratio at time
approximately 0.719.
t
Both magmas and their c~ystalliza-
t10n products will then begin to accumulate
arB7
will be
radiogenic
in accordance with ~heir Nb/Sr rat1os~
The ~Bub-
crustal~ granite would now have a sr87/sr86 ratio of
0.724 whezeas the ~crustal" granite would have a ratio
of 0.734.
The initial sz87/srS6 ratio at any point in
geolog1c tims t of any igneous rock now residing in the
crust is there£o%e a potential criterion for a crustal
or sub-crustal origin of this rock.
The value of the initial sr87/Sr86 ratio of an igneous
rock which is the produc~ of granit!zat1on
sediments depends on the nature of ~ese
not necessarily
lie on the developmsnt
of geosynclinal
sediments and dces
line of average
crustal stron~1um as indicated 1n Figure 1.2.
geosynclinal
sediments
rocks or the weathering
consist predomdnantly
If the
of volcanic
products of basic igneous rocks
'.,
-87of
sub~crue~al origin, the p~oducts of gran1tization
will
have initial sr8'/sr86 ratios lower than the crustal
average at that
1:1meo
On 'the ot;her hand, the 1n1i:ial
ratio could be higher i:han the average,
consist;ed largely of weathering products
rocks
if the sediment.s
of old 9i:an1~ic
0
The actual value of the initical sr87/SrB6 ratio of
such an igneous rock may be used to estimate
portion of sub-crustal
mi:er1al 1n 'the original
assemblage, particularly
if the
the prosedimentary
sr87/Sr86 of the continental
rocks a~ that: t:lme can be determined.
The developmen~
line for strontium in the mantle is
~rawn t~ ~he ypper limit of variation of ~e sr87/sr86
ratio in basalts as observedin this survey.
Assuming
that Figura 1.2 correc'tly indicates the time-variation
of
'the sr:87/sr86 rat:10 in the upper mantle, a sub-crustal
origin is i.ndicated for any igneous rock whose initial
sr87/sr86 rati.o at any time in geologic history falls
below this'line.
In order ~o detexmine the initial ratio of an igneous
rock it is necessary to know its age, its Rb/Sr rat10 and
i.ts present sr87/sr96 ratio.
If the age is not known,
the init.ial ratio ca.n be determined
by obtaining
a point.
of 1nters~ct1on of ~he develcpme.nt lines from two or
preferrahly
three ..whole rock specimens
Rb/Sr ratios.
.
Fina.lly,
/
of differing'
1f the rock has not been meta-
m<)rphozed after its czystal11za~1on,
'the initial
ratio
can also be found from the point of convergence of the
developmf!n~ 11ntas for t:he minexalscompos1ng
The ~i11 ty to distinguish
the rock.
igneous 2eocksof crustal
and sub-crust;al origin w~ll cont:r1bute matezoially to the
sQlution of ~any geologic problems.
meth,ad offers
a
n~
approach
of granite and will b::1ng
Bowen's classic
to the ~roblem of the C!r:1g1n
us
question;
~n~ how much metamorphic?"
Specifically ~he
closer to the. answer of
tQlrDW much gran11:e is
(1948, p. 80).
magmatic
'I'he dlstlnc~ion
between products of granl't1za'tion and igneous rocks added
- ~o ~e crust from ~hemantle in,orogenic belts will also
tilrow new light: on processes
of the continen~s
metl:1odcan .also
'the origin
be
of moun'ta1n fom8tion,
and many other. geotect.onic
'applied to ~e
of 'the porphyry
problems.
The
study of ore deposits&
copper. deposit.s,
assoc:1a~1f?n of certain types
gxcwth
of ore deposi
.'the pos~1ble
1:8
~1th J.gneous
~nuusives of crus:tal or sub-crustal origin, and ~be possible volcanic, sub-crustal or1gin of confomable,
sedimentary
PAGES (8) MISSING FROM ORIGINAL
Cu-Pb-Zndeposits
as suggested by Russel and stanton~
~9S9~ and Ofteda~l (1958).
The Differen~la'tion of Basal~ Magma.
When a body of basalt magma undergoes
a~ion, 'the resulting
crystal fractlon~
produc'ts w1ll dlffer among each otheX'
with respect to their Rb/Sr .ratios.
HOwever, all fractions
will 1~it:1allY ha.ve the sama'sr:87/sr86 ratio as theiX'.m~9matte source mat:er1al in the uppex mantle.
each fraction will develop
accordance wlth its
The increase
Thereaft.er
1'tsown 8r87/8r86
ratio in
par~1cular RbISr ratio.
w1~ time of ~~e
several igneous rocks which ~uld
sr87/sr86 ratio in
be' d.1fferentiation
produc~s of basalt magma 1s illustrated in Pigurel.3.
The slopes of ~he development
lines for ~e
different
types of plu~n1c igneous rocks or t:he1r volcanic equ1valents .were calculated
,using estimates
of tlleir Rb/Sr
ratios pr~senteClin C?hapter 2, Table 2.2.
'!'his metilod can be used to 'test. for commonparentage
of a series of r$olcanic or plutonic rocks of different
ccmposl~lons.
Co-magmatic igneous rocks
because .tbe strontlumdevelopment
fOB
an "array'
lines of all fractions
of the primary magma converge to a point.
as its
This point has
coordinates the ~ime when differsn~iat1on
occu&xed
and the sr87/sr86 ratio of the primary magma at "that tim9.
If certain igneous ,rocks w1~
unusual chemical composi~ionB
are foxmed by assimila~ion
of crustal material into part
of ~he parent magma, ~eir
development
converge
lines will not
'to a point w1~h the other fractions.
if a given association
differentiation
Moreover,
of igneous rocks is the result of
of more than one parent magma,
may also be discovered.
Two magmobodies
this fact
fonned by par-
tial melting of source material having dlfferen~ Rb/Sr
ratios, will l:'howa corresponding
sr87/sr86 ratios.
difference
in their
In genera~ the strontium development
lines of associated
volcanic
or plutonic
rocks, trea~ed
as possible "arrays., can be used to s~udythe differentia~ion of primary magmas under different physical conditions.
The method can also be applied to determine
relationships
~he
of lamprophyres, pegmat1tes and caZ'bonatitos
to the igneous rocks wi th YR1.~1ch
'they" are assoc1a'ted.
, instance,
those pagmatltles
products of residual
by other
For
which are crystallization
magmawill fit into 'the array formed
co-magmatlc fractions
of 'the paxent magma. On
'the other hartd, pegmatites
fo:gned as the result of solid
diffusion of ions (Ramberg, 1956) will not fit into any
array.
Their sr87/sr86 ratios will instead resemble that
.of 'the country rock •.
Carbonat1tes
limestone
have bsen 1nte~J:et:ed as xenoliths
(Shand •.1947), as crystallization
carbonatic liquid of magmatic origin
and as products of hydrothe~al
of
products of
(Pecora, 1956)
solutions
(Bowen, 1945).
All three theories may be applicable to certain carbona1:1tea.
By determ1ning in!t.tal sr87/sr86
carbonati1:e, ~he associated
limestone occurrences,
"&
igneous
ratios of t:he
rocks and possible
choice bet~~en the various
hypothesis may be made. If a carbona'tlte
can be shown to
font an "array" with 'theassociated igneous rocks
"in
an
area whe~e the s~87/sr86 ratio of the limestone is measurably different,
a co-magmat:icrelationship
between the
carbonatite and tile igneous rocks 1s demonstrated.
This
1n~erpret:at1~n is consistent. with the results obtained
in Chapter 8 for 'the intrusives
and 'the carbonati1:e
of the Monteregian hills
a1: Oka, Quebec.
-93-
The Composition of the Upper Mantla~
The abundance of radiogenic isotopes in rocks of
known sub-crustal
origin can be used to calculate
o~ the parent to daughter eleme~1: in ~e
.For instance,
2Sbaaalt1c
according
ratios
upper mantle •
to the average sr87/sr86 ratio in
rocks ~be average Rb/Sr ratio of the source
material in the upper mantle 1s 0.039 and ranges from
0.022 ~o 0.051 (Chapter 6).
Slm11ar irafoxmation could be obtained for the RICa
ratio as well as the .U/Pb and Th/Pb ratios of the upper
mantle from measurements
prlate radiogenic
~e
of the abundances
of the appro-
isotopes.
possibility of using the abundance of Ca40 in
~
Recent basalts to calcula~e ~~a ra~os
mantle merits. particular
OU~
attention.
for the upper.
In order to carry
such a calculation the primord1alabundance
must be known.
analyzing
Pasamonte.
of
Backus (1952) a'ttempted to do this
the calcium in theachondrit1c
ca40
by
meteorite
Al~ough he did report a slightly lower
abundance than is found in calcium reagents,
his measure-
ment was of poor quality and 1s not conclusive.
Prom measurements of
the abundances of
sr87
and Ca40
in basalts 1~ is at least theoretically possible ~o calcula~
Rb/$r and RICa ratios for the upper mantle.
other hand, it bas been demonstrat.ed
ratios are ~la't1valy
On the
'that K/1U3and Ca/Sr
constant for each rock type.
Since
the upper mantle can. be composed of only per1do~lte,
eclogite or dun1te for various geophysical and geochemical
reasons,.1t
of the
should be possible to make reasonable es~ima~es
it/1Q) and ca/sr ratios for the upper mant:le.
these assumptions concentrations of Ca, Sr,
« and
Wi th
Rb could
be calculated.
Evidence is presen~ed in Chapter 6 'that the lavas
in Hawaii may be drawn from ~wo
extruded by volcanoes
sou:ces
differing
respec:t1va sr87/sr86
in. ~ei:.
in ~e
slightly, but perhaps
8bund~n~
of vertical
of
sr87 could
variatlons
ratios.
.s1gni.flc:ant:ly,
Such difference
be explained
as evidence
in the rubidium concentrations
of
the mantle.
Pu'tUX"e work may show that
are unfou~ed or impractical.
Bome of
these
sugges~:1.ons
'!'hey are recorded here 'to
sttmulate adiscusslon of 'the many possible inte~retatlons
of the variations of ~he abundance of radiogenic isotopes
1n rocks.
:fHE__qOi:1CE~1~~~!;IOt:~~ 9?
At-ill 9TJt0~~~IY~
Xt~ IGt~OtJS AtID SEDlti]Ei;l1TARY
ROcKs
~~~~'"'--"=
~
AND
I
'J
Tf<m
CRUS'!"
ODI
THE
EARTfi"
~
.
!ltJBJ])1.~
'
tnedJncentrationf:f
sedimentary
'{'
'~select.ion'
.
,made accord1tig
1.,
2.
some 250 refeX'encea
rockS.
'this search.
"
of rubidiUm arid, strontium
,"
in igneous
wer,;e conaulted
of the available
and
in
analyses 'Was
.'
't~) the
f~llowin~
criteria:
Only'analyses having precis'ion errors
'better were chose'no
of
'1; 15% or
All analyses which give no ,indication of p,recisicn
calibration of the mathod were discarded.
erxors~r
for the concert1:rationa of rub!d'ium and
s.'tront1um war~ ~alcul!lted in te;ms of parte per million
,3,. "Average values
by, .weight.'
The' ',analyses, we&'e we.ighted in
the
average
:'according'
to the number ,of different samples ~epresented. '
.
'
,
,
and the values which were finally chosen are f~om analyses
publis~ed mostly since about'1~50.
case' ofaeep
with precision
s'ea' sediments
and ul't:rabcus1c ' rocks,
er&'ors greater
for lack of better data.
Occasionally,
as in
the
anal~~es'
than t: 15% had to be included
~96C3
.I~
•.
""'."'."~------------------~~-------------~-
the concent~ations
aedin~ntary
of ~ubidium
zacks is essential
the abundance
and strontium
and
to a ~eliable evaluation
of sr8? in the crusto
culated will be combined
in igneous
of
The averages h~re cal-
in certain propo~t1ons
according
to the crustal model of POltlervasrt in ordez to estimate the
RbISr ratio of the continental crusto (See page 118)
The sr87/sr86
ra~io of igneous rocks of sub-crustal
origin can be used with certain assumptio~s
to calculate
Rb/Sr ratio of the magmatic source material.
Comparison
the
of
this calculated value to average Rb/Sr ratios of various
types of igneous rocks eervea to identify the nature of the
sub-crustal source material.
The Concen~~a~1ons
of R~1di~~
6~d1~ntarv
In the foll~~ing
and S~rontium in Igneous
Rocke~
pages, Table 2.1, the super1o~
and
rubidium
and st.rontium analyses for igneous rocks are tabulated.
~able includes the author~ year of publication,
method, the number of samples represented,
of rubidiwn and strontium
in parts
The
the analytical
the concentrations
per million
by weight
(ppm)
as well as remarks about the nature of the material analyzed.
Weighted averages are calculated for each rock type.
summary of the results
The presen~ation
A
appears in Table 2.2 on page 106.
of the data on sedimentary
rocks is
e~actly analogouse
n a~ma~
and general conclusions are
found on page 13:1 , Table 2 e .130
Table 2.1
Analyses of Rubj.diUfi'l and Strontium in
Igneous Rocke and K9teoritea
Superior
Aul(:hor and Method of No. of
Reference'Analys~.s
Granite
Ahrensat
Samples-pPM
198 150 New England granite
correct1on,applied.
O ..
Sp.
50
aoo Calibration by I.D.
on G-l and tAJ-l
Turekian and O.Sp
Kulp,19S6,p
O.Sp.
100 Grani'te
Ca 0.1 - 1.0%
85
4
534
6
219
6
209
ai, 1956
..
..
"
332
HoX'stman,
pp~
29
1955b, p532
Taylor et
Remarks
O.Sp.
ai, 1952
Turek1an,
Rb, Sr
9~anite,St. ~ustell,
Cornwall
Granophyre
Slieve Gullion
porph.felsite
Slieve Gullion
Granite
Wes~ Mourne Mountain
F"Ph
66
170
granite
OoSp.
90
257
granite
I.D.
27
I.D.
so
133 348 Composite of Finnish
granite and 9rani~e
gneisses.
125 283 Precambrian granitic
1951
Sazhina,
1958
Gast, 1960
•
and 9~~issic rocks
from Western U.S.A.
Table 2.1 continued
Author and
l>~thod
of
No. of
Sr
ppm
Rema&"lts
Reference
Analysis
Sall!lplea
Dem1n and
Kh11:arov
F.Ph
4
138
..
4
164
Ccux:sa 2 mica a::3d
~crocline. g~ani~e
leucoeratic 9gaYd~e
187
Caucasus,
Alaski te dilte
1958, p. 124
..
2
Caucasus
Kat.chenkovtat a1a.9.Sp
1958, p.226
0
457
4
Granite, Eastern
Russian Platfo~
196
(290)
weighted average
for granite
197
(245)
Granod1orit;~
Tayler at
al, 1956
O.Sp.
7
'l'urekiat;1 and
O.Sp.
as
granodiorite
Slieve Gullion
Armagh
126
440
Ca 1.0 - 5.0%
KUlp,,_ 1956
Demin and
P.Ph.
108
granodiorit.e
Khltarov
195~, p.724
weigh'ted ave~age
for 9%ancd1orl~
Por'phyro1a
i22
440
(9) (85)
Table 2.1 continued
Author and
)llefefence
AS..ethcd of
Ana~ys1s
No 9 of
Rb
sampl~~. ppm
w
Sr
p~m
~venite
O.Sp •
.Taylor
1
105
Syenite
8
147
Trachyta
3
110
Syen:tte,
C.,Sp.
953
1
150
Z.D.
1
140
et ai, 1956
A
p.225
Horstm~n',
1957
Wager and
~U.tehello
p. 218
>'
' ..
Faux-sand
Hurley
250
"L'racbyte
,
(in press),
Weighted average
for syenite
136
156
(14)-
(2)
'Andeeitea and Diorites
Tayloret
O.Sp.
7
12
.nndssite, New
zealand
Ph
9
88
TOhali~e from th~
'al, 1956:,
, p~22S
Ttlrekian and
I(ulp, , 1956
F
f)
Mal~ya,Laba
massifj.::, Caucasus
Horstman,
1957, p.ll
F.Ph.
Weighted average
for'andesites and
diorites
5
'diorite'
110~ lS
88
(21),
500.
(13)
Table 2.1 continued
Author and
Refe~ence
l~ie'thod of
i\n~tX81B
Na
of
o
Rb
Sr
Remarks
ppm
Sam2!.es
Basalt.ic Rocks
Ahrens at
aL, 1952
OoSp.
Fairbairn et
f).Sp.
8
49
(40)
1953,
p. 43
al.,
Gabbro. Co~~ection
applied
41
(57)
Ontario diabase
Correction applied.
183
TUrek1an,
1955b, po532.
a.sp.
50
500
Baealt
Tureltian
O.Spo
244
467
Basalt
O.Sp.
13
&
Kulp,
1956, po267
Taylor at
al.,
1
1956,
34
9
Basalt
Gabbro
30t:. 18
G~bro
p.225-226.
Horstman0
F.Ph.
15
19570
Cabell and
R.Act.
1
O.Sp.
8
Skaezgaard,
fayali1;e
ferrogabbiro
21.9
Smaleso
1957, p.40).
Katchenkovet;
430
Gabbro - norite
East.Russoplatfo~
al., 1958,
p. 227.
Gas~, 1960,
83
p. 1290.
83
83
•
Paure, 1961,
Ph.D. Thesis
I.D.
..
at M.I.T.
Weighted average
for basaltic rocks
2
1
1
26
30
32
460
469
454
Composite basalt I
35
273
Tholeei~ic basalt
7.0
8.0
346
262
Duluth Gabbro
NQrite, Bushveld
Complex
32
440
(331) (612)
..
It
It
..
II
III
Autho&" and
Refa 1:'ence
l<iathcd of
1:010 u of
An~YElis
Saru~les
Gast,
I.De
RemarltS
1
0.9S
1
6~45 312
Olivinebasalt
Hawaii
9
21.5
Olivine basalts
102
1960, p.1290e
..
C)
Faure, 1961, IoD.
Ph.D. Thesis,
492
Olivine basalt
~d-Atlantic Ridge
from oceanic
islands.
M.I. '1'.
Weigllted average
for olivine basalt
18
(11)
440
(11)
6.9'
149
Eclocri'te
Paure, 1961,
I.D.
1
Ph.D. thesis,
M.l.T.
Eclogite xenolith
from k!~.berlite
pipe, Robart
Vict.or Mine ,
S. ld!rica.
pltrabasic Rocks
Ahrens e~
OeSp.
al., 1952.
R
All values corrected by
factorl 0.45.
13
1
Ultrabasic rocks.
M1ca augite peridotite. Murfrees-
0.9
495
boro,
•
Arltaneas
Kimberlite,
171
S. Africa
a.sp.
4
0.9
p.254
..
All values corrected
by factor of 0.61.
dunite, coX'rection
applied
Serpentine
2
1.2
Websterite and
Pyroxenite
Lherzolite
Rlmberlita, S.Africa
Pinson et
al.,
1953,
..
1
1
12
170
Aui:hor
Refeg'~nce
~
iiO. of
Sr
-~~l?1&13
p~
!~ra'tbod.of
and
l\na]J!~F!
:RIIio~'"""'T'''-
Pinson et
al., cont•.
O.Sp.
Remarks
90
1
ea'
1
F.Ph.
5
lO:t 10
Faure, :1961, I.D.
Ph.D. Thesis,
1
0.•6
379
M.l'. '1'.
1
0.5
49
.lD
Horstman,
Mica augite
peridotite
Murfreesboro,
Arkansas
Anorthosite
Split Rock, Minn.
117
Ultramafics
1957.
..
Anorthosi~e
Bushveld; Complex
ey'roxenlt:e .
'Busbv~ld C~ple:(
~~syntbe-~.i~
..is..att~mpted
."""-"'."
..,.~~"~-"'_ ..... _.,~......
_ _,-~..:. _._ _"---
_-~.",.~~,._..
..
...
..
...
.......
-- ~
........... "'~....
for ultraba~ic rocks in general';'"
.,
AnOri:hosite
O~6
.171
495
170
QO.
.49
0.5
-------~_. -----.;..,_ ....---
.K1mbezo11 te , S. Africa
. Mica aug.i te pe:tldoti'te
.pyroxan1te
~~dr1t~
J~teori~es.
Meteo.r1'te MethOd 'of
Analysist.
Forest.
City
".
"
..
...
280
I .• Do
I.D.
N.Act.
, X.D.
N.Act:•
I.p•.
Average Porest C~ty
Analyst.
Rb
Sr
PPJR
ppm
3.5 '.
3.91'
. 9«»8
~rZ09 et al., 1956,p.558 •
11.9
Schumache~, 19'56, p. 5460
webster et a.l •• 1957, p.544"
3.04
2.90 .
10.2
3.04
. (6)
...
Cabell and Smales. 1957,
. p.404~
Gaa~, ..1960, p.2 •
2.75
3.19 .
"
10.6
(3)
Table 2.1 continued
Sr
Me~eorita Method of
Analysis
Chondr1tic Meteorites
I.D.
HOmestead
Analyst.
p~
continued.
3.6
10.6
Herzog and Pinson, 1956,
p. 5S8.
Cabell and Smales,
p. 404.
R.Act.
3$15
Average Homestea.d
3.37
10.6
(2.)
(1)
II
Modoc,
N.Act.
2,,97
I.D.,
3.45
Cabell and Smales, 1957,
p. 404.
Gast, 1960~ P. 20
Scoi:~ Co••
Kansas.
Average Modoc
19574
3.,21
(2)
Ness Co.
f
N.Act.
Cabell and Smalea,
2.90
p. 404.
Kansas
N.Act.
2.28
Long Island,N.Act.
2.11
Faba, Co.
..
1'1
Limexick
It
Phillips Co.,
Kansas.
Beardsley
I.D.
4.90t. .06
Ninlnger
I.D.
4.83:1:: .06
Richardton
I.D.
2.96
Holbrook
I.D.
2.22:t .04
AtmM 1162
:t.D•
2.3
Gast, 1960, p. 2.
••
1349
oj;
.035
n
..
19574:
Table 2.1 continued
l~teori te ~%thod of
Analvs~s
Analyst
lro)
0
PI!;lD
Chondr1tic ~~teo~1tes continued.
2.9
3.5
Quoted from the 11tezostura by Gast, 1960,
3 ..9
P. 2.
3.8
Average .fit\1HM
(3)
weighted average for
3.17
chondrit1c meteorites
(12)
10.6
(2)
Aehondr1t1c ~~teo~ites
Pasamonlte
gxey phase I.D.
white phase X.D •
white ~hase IoD.
Average Pasamoni:e
e9.5
0065
94.7
0.50
O.21(~)
0.31
grey phase I.D.
bo'th combined
0065
'0048
Ruevo Laredo I.D.
Oc 37 (2)
Sioux co.
0.18
X.D •
•
tt
C...ast. 1960. D. 2
94.7
89.5
92.1
(RbISr:: 0.005)
Gast,
1960, p. 2.
•
N1nlngsr 298 I.D.
0.29
n
If.ooreCounty I .Do
0.16
n
Johnstown
..
I.D.
N.1\c1:.
Average Johnstown
1956, p. 546.
"
phase I.D.
~ite
Schumacher,
0.105
0.04
0.72
2.07
Webster et ale , 1957.
P. 544 •
2.07
-105-
Table 2.1 continued
Meteorite Ma~hcd of
Analysis
Sr
Analysi:
ppm
Achondritic Me~eorltes continued
*Bluff,
Faye'ttG
Cabell and Smales, 1957~
P. 404.
1.01
R.Act.
Co.,
Texas.
Weighted average for
achondritic meteorites
0.37
(6)
92.1°\"1
(1)
eOm1~ted from average.
~~Gast, 1960, p. 1290, on the basis of previously unpublished
data gives value of 74ppm.
I.D. O.Sp. -
Isotops D~lution
Optical Spec~roscopy
F.Ph. N.~ct.-
Flame Photcm3try
~eutron Activation
Table 2.2
suw~ary of Rubidium and.S~rontium Concentrations
in Igneous Recks.
Rock
Rb PPiU.
TvJ')e
RbISr
Sr p~
197 (245)
1.00
440
(8S)
0.28
(14)
156
(2)
0.87
(21)
500
('13)
0.18
440 (612)
0.07
(11)
0.04
Granite
196 (290)
Granoa:Lorlte
122
(9)
Syen1t.e
136
Diorite & Andesite
.8S
Gabb:t'o & Basalt
32 (331) .
011vlne'Basal~
19
(11)
440
BClogite
6.9
(1)
149
(1)
0.05
Anorthosite
0.6
(1)
280
(2)
0.002
171
(1)
170
(1)
1.00
IUca-auglte peridotite
495
(1)
80
(1)
6.20
Pyzoxeni t.e
0.5
(1)
49
(1)
0.01
0.9
(4)
10.6
(2)
0.30' .....
-.
(1)
)
K1~rlite,
So
Africa
Dunl'te
--_.--"-'~.. ... ~
-
3.17 (12)
./Chondrites
!
0.31 ... (6) ..
~,___
~chondr1 'tea
Figure in brackets
indicates
sented in the average.
92.1
_~~"'"'''''''''
__
'''.'_'_'''
0.004" ../
_._
.• _
.......
'4-~,
the number of specimens repre-
'/
Cl
~'j
t {
~wmna&Y.
The data foE' syenites and vazoious types of ultrabasic
rocks are not as p~GC1Be and xepresentat1ve as those for
granite and basalt.
A
plot of the concentrations
Sr, K, and Ca in cert.ain
_Figure 2.1.
Syeni tee
-quality -of tbe data.
of Rb,
types of igneous rocks appears in
WSE'e
om1 toted because of the poor
arhe concentrations
of
K
and
Ca
we~a
taken from Ture1d.anand ~Jedepohl (1961) w1i:h the exception
of 'the values for dio~lte and andesite which are from
Poldervaart:
(1955, po 134).
The pattern
resembles many of the variation
diagrams publ1sbed
Nockolds and Allen (1953, p. 105).
confirmation
1s quite
normal and
by
This 1s a qualitative
that the average rubidium
and strontium
centrations here calculatsd are of the eor~ct
con-
order of
magnitude and bear the proper ~elat1onship to ~he major
constit.uents.
The concGn~rat1ons of Rb and ~ increase un1fo~ly
the more acid rock types.
high in the basaltic
~ocks.
in
em decreases steadily from a
Stron1:ium, however, increases
at flrs~ and ~ssumas a maximum value in andesites and
diorites.
patterns
Nockolds and Allen (1953) repol:ted similar
for rocks
from East. Central
Sierra
Nev!1C1a(Pig.
13d,
-108-
...
0
0
(f)
0
0
0
0
'"
It)
0
0
It)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
V
rt)
",
10
C\I
0
0
0
0
0
0
0
0
CD
0
0
0
0
0
U)
CD
10
10
10
V
0
0
0
0
0
0
..
0
0
0
0
en
0
en
co
10
0
(f)
~
0
0
~
Q.
Q.
tS
0
0
~
0
0
(f)
0
0
"..a
.,,,
0::
.l(
..
....
....
CD
",
....
d
,,
...... ~/
./
...........
~
",.
,.......
I
d
/
,
............
.....
........
•,
,,
/
/
/
;I'
....
,
/
/•
I
a:
C!)
,
\
z
a:
\
C!)
,
,,
W
....
\
~
0
W
Z
\
\
\
4
\
\
.,..'
01\
-,
\
\
~\
/
0
....
<t
....
,,
,
Z
LLI
\
\
•
•
z
(f)
0::
~\ ,
\
\
\
/
0
C/)
\
\
..0
0::
lJ..
\
\
\
/
..
..
0
0 ~
4 (f)
,,
/
0/
tS
52 ~
,,
,,
tS
b
z
~ Z
c
\
I
(!)
w Z
....a: <t
I
•
'J(
/
/\,
I
\
....
0
.............
/
\
0\
w
I
/
\
Z
•
'y'
/
ILl
0
0
~
\
/
\
0
I
""
I
I
~
I
...........
x
I
",
/
.......
,,
"/
V
(f)
::)
0
C\I
............
",
./
V
0
d
0
d
q
q,
0
",
0::
~
!J
4
C/)
4
m
0
z
0
0
t\I
~
..a
0::
0
0
0
0
0
",
C\I
0
0
0
V
U)
~
~
0
0
0
0
0
0
0
0
0
0
0
LLI
0::
::)
(!)
0
LL
0
0
N
0
ex>
0
CD
0
0
V
N
0
0
0
0
CO
CD
0
V
0
N
po134), the Sco~tish Caledonian (Fig...
13c,p.135), the Scottish
Tertiary alkali basalts
(1954,F1g.28a,p.272),
the Hawaiian
alkali basalt-t.rachyte sexies (1954"F1g.28b,p.272),
polynesian
alkali basalt-trachyte
and the
series (1954,Plg.28c,p.273)o
On the other hand, a steady decrease of calcium as well as
strontim~ as a ,function of (~81 K)-(Ca Mg) was observ~d
rocks from the Southezn California
Batholith
p.133) and the lava series at Lassen Pe~t
p.133).
in
(1953,F1g.13a,
(1953,Fig.13b,
The maximumin 'the strontium concen~ration is also
lacking in the d1fferentlationproducts
of thqlee1t1c basalt
magma (Nockolds and Allen, 1956).
The last. mentioned
tion for the
t\~O
authors give 'the following
types of behaviors
accauodated in ~e
Strontium can be
feldf3par st.nctur8 as a replacement of
calcium in plagioclase
and potassium.in
S~ront1um cannot, however,
mineralS
explana-
replace calcium in ferromagneslan
(Nockolds and Mitchell,
crystallizes early, ~a
potash feldspar.
1948).
residual li~1d
If plagioclase
iseteadl1y depleted
in strontium and the lat.er acid fractions will contain progressively lower concentrations of strontium.
that ferromagnas1an
1s concentrated
minerals crystallize
in ~e
In the case
first, strontium
residual liquid and thus attains a
maximum
value b0fozoe it is g>emoved by inco~oZ'ation
inl:o the
feldspars.
The
Rblsr ratio incr~ases smoothly from basalts to
granodiorites
but rises
ahazoplyin granites.
result of ths extreme differentiation
tium in the more acid rocks.
This is the
of rub1d1u~ and st~on-
t~ile strontium 1s deple~ed,
rUbidium becomes concentrated in the gesidual magma~ic
liquias.
Thus acid volcanics
ratios as high as 35~
(obsidians)
may have
Rblsr
(Professor W. H. Pinson, oral commun1~
cation).
Table 2.3
Superior
Author and
Refsrence
MethOd
Analyses of Rubid1um. and Strontium in .
Sedimentary Rocks
of
Analysis
No. of
Saq&ples
!lb
Sr
}:)pm
TJJX[l
Remarks
-
Shale
Heide and
Shale
227
O.SpCl
3
O.Sp.
35
245
69
.300
~:r1st.,
1953, pCl327
Turekian and
Kulp. 1956,
•
Non-calc. shale
r.veJ:a9~ shale
p.287.
Horstman, 1957.P.Ph
Weighted average
for shale
26
140:t50
149
(29)
Sbale
300
(69)
-111-
Table 2.3 continued
!-1ethoo of
Author and
Reference
Analysis
t~o. of
S2.&~pw-lea
lRb
Sr
p~m
ppm
RemaX'ke
Limestone
Heide
ana
o.sp.
5
60S
Muechelkalk
O.Sp.
155
610
Pure limest.one
Christ, 1953.
'J.'Urekian and
Kulp,
1956,
p.290.
HOrstman,
1957.F.Ph.
7
<5
<5
We19h~ed average
for limestone
Limestone
610
(7) (160)
Sandstone
HOrstman,
1957.F.Ph.
'l'urekianand
Kulp, 1956,
po 284.
4
60t 61
Sandstone
< 20
O.Sp.
Weigbted average
for sandstone
60
(4)
Estimated from Sr
constant of ~Aa~~2.
<20
Dee~ Sea Sedimants
Clarke, 1924. Ch~An.
Hevesyat
X.Pluor.
Sl
470
Red cla¥ compos:tta.
1
760
Red clay
Challenger st..3S3
1
254
al., 1934,
p.313.
Horstman,
1957.
q
P.Ph.
II
4
160
4
60
..
It
253
Composite red clay.
II
II
Table 2.3 cont1nl:~ed
Author and
Refex-ence
Pl~~hoo of
!:Go. of
S:c
Analvsia
S.C1mp}..es
pmn
litemarks
Deep Sea Sediments 'con~inued
Turskian and
O.Sp.
2075
10
Kulp, '1956,
p. 289.
Goldberg et.
al.,
1958,
Pleis~ocene sadiment from Atlant.i.c
Core A 180....
74
0 oSp.
710
35
Pecif':tc Pelagic
sediments
p. 170.
110
weighted aV6%aga for
deep sea clay
Horstman,
(8)
F ..
Ph.
6
a.sp.
3
720
(98)
10
Globigerina
oozeu
1957.
Goldberg et
800,
al., 1958.
0
Weignted average for
91objge~ina ooze
Ocean
~ac1£ic foram. &
globiger1na 00Z9
10
800
(6)
(3)
t"lat:e%'
Heide et
O.Sp.
1
13t"l
Sea water
al., 1953,
p. 327.
Smales and
R.Act.
"'-.Salmon, 1955.
Smales and
~lebster,
p. 139.
1957,
I.D.
1
O.117.!:.Ol
4
o .11St.OOl
r ('.
Nor~h l1tlantic
49002IN,lSo19°t-;',
depth 400 m.
Table 2.3 con'tinuetl
Autl'lO&'
and
Reference
R<2ei;1!oo. of
.Analvsis
Remax:ks
No~ of
SamDl~s
......... .
,.:~
Ocean Water continued
Pinson at
al., 1957.
p. 1781.
1
. I.DIt
~115 7.2
.019
8117
h~lghted avegage fog
.6
Surfa.ce water:
66018 ow, 39001°N
7.2
(3) (1)
sea water
Qamitted from tile average.
Ipotope Dilution
Optical Spactroscopy
Neutron Activation
Flame Photomatry
X-ray Fluoraac~nce
I.D.
O.Sp.
R.Act.
If.Ph.
XeFluor.
Ch • .nn.
~
Che~cal
Analysis
The ~esul~s of the compilation for sedimentary rocks
a~e summarized in Table 2 4.
0
Compilations
of analyses of trace elements
literature such as this one have been undertaken
investigators.
from the
by other
The most recent of these are by Vinogradov
(1956) and by 'rure1t1an and wedepohl
(1961).
Table 2.5 is a
comparison of the results obtained here to those repor~ed in
the othe% t~o surveys.
Table 2 4 Summary of Rub!di~~ and St~ontium Concen~xations
0
in Sedimentary Rocks.
Rb~pm
Reck Tvpe
Sr ~Qm
nb/sr
0.50
Shale
149 (29)
300 (69)
Limestone
<5
(7)
610(160)
Sandstone
60
(4)
110
(8)
720(96)
10
(6)
800
(3)
0.012
(3)
7.2
(1)
0.016
Dee~.sea clay
~lQb~96~1na ooze
Sea water
0.117
Turekian and Wedepohl
<
< 0.008
20
...v
3
0.15
(1961) degived most of their data
for igneous and sediinentary rocks from HoX'stman (1957),
Turelc1anand Rulp (1956), Gast (1960), an~ Goldberg and
1\rrhenius
Their values agree w1tl1 ~ose
(1958).
in this s'tudy wl-th only a few exceptions.
obtained
The concent.ration
of strontium in ultrabas1c zacks, for instance, is certainly
greater than 1 ppmo
ratio
A
value of 6 ppmwould give a Rb/Sr
of 0.03 \sJb1chis about righ't for magmatic source
material in the upper mantle.
V1nogradovOs
compilation includes results from many
different sources without any selection of the more reliable
analyses.
His values
aX'etberefore
thoso of Turekian and Wedepohl
O~
lass
truat-worthy
this autho&".
t.han
-115-
Table 2~S
Concentra~ions of Rubidi~~ and Strontium
in
Igneous and sedimentary Rocke.
'l'his author
Rb
ppm
Sr
ppm
Rblsr
Granite
196
197
Grano-
122
Turekian et
Vinogradov,
ale • 1961
1956
RbISr
Rb
Sr
ppm
pptn
1.00
170
100
1.7
4.9~O
0.28
110
440
0.25
136
156
0.87
110
200
0.55
Diorite &:
Andesite
88
500
0.18
Basaltic
32
440
0.07
Rock Type
Rb/Sr
Rb
Sr
ppro
ppm
400
300
1.2
70
800
0.09
45
440
0.10
diorite
Syenite
30
465
0.065
rocks
0.2
Ultra-
1
0.2
2
27
0 ..07
5.S
20
0.28
maf1cs
Chondrites
3.17
10.6 0.30
Shale
149
300
Limestone
<5
610 <:,00008
Sandstone
60
< 20
Deep sea
110
720
0.15
10
800
0.012
0.111 7.2
0.016
0.50
A'3
140
300
0.47
3
610
0.005
60
20
110
180
3
0.61
clay
Deep sea
carbonate
Sea water
10 2000
0.005
Zhe Conc~nt~~1o~s
of RubiditIm and S~~on~1um
in the $g-uat of ~he Ea~th
~In~roduc'tion.
---
In orda~ to calculate the concentration
of the~ements
in the crust of the eagth estimates must be made of the p~oportions of the var~ous types of igneous and sedimentary
rocks in the crust.
Knowing the concentrations of ~e
ele-
ments in these rock types ene can then arrive at a fi9u~e fog
the concentration
of each element in the cruste
This 1s a problem of considerable complexity and gsochemical 1nteres~.
Contributions
been made by many geochamdsts.
approaches
t:cywardsits
solution
have
Basically ~bree different
have been 'triads
1.
Geochemical balance calculations.
20
Bstimates based on ~e proportion and composition of
roclcB exposed at ~he surface.
3.
Detailed analysis
of the surface of the earth
and
definition of certain regions having characteristic
reclc assemblages.
Geochemical
balance
calculations
are based on 'the assum-
pt10n that the amount. of any eleman~ released by the weatheg-ing of igneous rocks is equal to 'the amounts incorporat.ed
sediment.s and dissolved
in the oceans.
Calculations
in
of t;b1e
.3
.nat:ure have been made by Goldschm1dt (193~),
Correne
(1948),
Kuenen (1941), Wi~~an
(19580
(1954) and Goldberg. and Ar~henius
Each authoIl:'
suggested ceztain refinements
basic pre~seo
Kuenen (1941) first drew attention to the
importance of deep sea sediments particularly
chemical balance of calcium.
set limits
of uncertainty
Wickman
deep sea sedi~nts
Goldberg and
their analytical zesuits for
into the calculations.
tion of several simultaneous
igneous rocks weathered
to the 980-
(1954) att.empi:ed to
to the results.
~~rhen1us (1956) inco~ozated
be obtained.
of "the
From the solu-
linear equations
and sedimentary
amounts of
rocks formed can
The method has the following difficultiesl
10
No allowance is mads fo~ erosion and ~acyclin9 of
sediments.
2.
'l'he e1.emen'te now dissolved
to be derived ent1xely
in the oceana are assumed
from weathering
of igneous
roclcs.
3.
all~Jance
material.
4.
The propoxtions of igneous rocks and sediments so
calculated apply only .to the rocks having the part1aula: composition used in the calculation.
No
is made for the addition
The second met.hoa
ployed frequently
is moxoearbitrary
because of its
chemists have made and used their
example, Mead (1914), Clarke,
of volcanic:
but has been em-
simplicit.y.
Many990-
ownestimates.
See,
(1924,p.29), HOrstman
for
(1957),
dtXX8-
Turekian and Kulp (1956).
Many of the la~er estimates go
back to Cla~ke (1924) who p~oposed the following composition
for a crust 10 miles in thickness:
95% igneous rocks made
up of granite and basalt in the ratio of 2:1D 5% sedimentary
rocks \'lhich are
.An average
ratio
ao~
shale,
15% sande'tone andS"
igneous Z'oclccomposed of granite
of 2:1 is equivalent
therefore take granodiorite
limsstone
and basalt
to granodiorite.
G
in the
Somegsoch(!m!s1;s
as the most representative
the average ccmpoai~lon of the continental crust.
of
(Turekian
and Kulp, 1956).
The third approach 1~ the most satisfactory and is used
here.
The besi; crustal
(1955).
model is
that
proposed by Polde&"vaa~t
In the following sec~1on this model will be described
in soma detail and the concentrations
t1um in the crust
\'l}111be calculated
poldervaart°s
of rubidium and st~onfrom it.,
l(odel. of the Crua~.
~troduction.
POldervaart (1955) p~oposed ~at
the surface of the
earth can be subdivided into five regions each of which
consists of igneous and sedimentary
sitions and in certain proportions
rocks of certain compoappropriate for the
particula~ envi~onmento
He assumed that metamorphic
sedi-
ments can be included with the igneous rocks in such a
model.
'Ene five r~gions of the earth are:
1.
Deep oceanic
Continental shield
20
3.
4.
5.
Young folded belt
Suboceanic
Volcanic island
por each of these ~eg1ons Poldervaart estimated surface
azoea, depth 'to 'the Moho, proport1on
rocks and their compositions.
publlshad
information
of igneous
These estimates are based on
in the geochemical
\'1S11documented in POldervaartOs
to aadimantaE'y
paper.
by him need no. additional justification
literatu3:e and azoe
The values
adopted
and are accepted for
the presen~ purpose.
Deep Oceanic Reqion.
Thi~ region includes the deep ocean basins which are
268 x lOG km2 in area.
~km,
The average aep'th of water is
foll~~ed by 0.6 km of unconsolidatea
(0.3 km solid)
sedtmen~s and 5.75 km of a rock whose compressional wave
velocity
is 6.5 lan/sec.
The to~al depth to the Moho1s
10.75 km on the average.
The total volume of the sediments (solld) 1s 80.4 x
106 km3 with a mass of 217 x 1015 tons at a density of 2.7.
-120-
This mass of sediments consists of 104 x 10
calca&'sous sand and ooze
17
15
~ona of
82.5 x 1015 t.ons of red clay
and 30.5 x 1015 tons of siliceous ooze.
The layer below the sediments 1s assumed 1:0 bs an
olivine basal~ wi~h a de~s1ty of 3.00
1540 x 106 kin3 with
Its V01UWB is
a mass of 4620 x 1015 tons.
The
~otal mass of the oceanic crust is 4837 x 1015 tons.
The calculations
centrationB in ~e
2.6
of the rubidium and s~rontium con-
oceanic crust are summarized
~ne concentrations
calculations
1n ~gble
used here and in allsUbse~ent
are those derived
from the survey of the
literature.
Table 2.6
Concsntra~1ona of Rubidium and Strontium in
the Oceanic Crus~.
Rbx':'
100
Sr x ~
" ~Jt ..
!U)ppm
96
18
440
17.2
421
Calc. ooze
2.15
10
800
0.2
17
Red clay
1.71
110
720
1.9
12
Sil. ooze
0.63
60
<20
0.4
Roek TYPe
Olivine Basalt
Totals
J)pm
1907
100.49
Best estimates
Sr
I
Rb
:g: 20 ppm
Sr
=450 ppm
=-0.045
Rb/Sr
100
450
Contingntal Sh1eldReqion.
~~e a~ea of this region is es~imated at 105 x lO~2~
its elevation above sea level is 0.75 km, the averaga
thickness of sed1mantagy cover is 0.5 km (solid) and the
depth 'to the Mohoi a 35 lon be lO\fJ sea leve 1.
The volume of the igneous
rocltS is
3700 x lO~3.
Their composition 1s exp~essed in terms of g~anod1o~ite,
diorite and basalt in the proportions
2300 x l06km3 9ranodior1~e, 300 x
1100 x lO~3
basalt.
Ass~n9
and 3.0, respectively,
1015 ~ons granod1or1te
x 1015 tons basalt.
7.67:113.67
lo~an3 diorite and
densities of 2.7, 2.85
tbe mass distribution
6
O~
is 6200 x
850 x 101S' tons diorite and 3300
The total mass of the igneous rocks
is 10~350x 1015 tons.
The volums of tbe sediments
weight of 140 x 1015 tons.
1s 52.5 x lO~3
They are constituted
41% (51.4x 1015 tons) shale, 4~
of
(60.0 x 1015 tons)
sandstone and 16% (22.4 x 1015 tons) limestone.
combined weight of igneous and sedimentary
10,490 x 1015 ~ons.
with
The
rocks 1s
a
Table 207
of R~u>idiTh~and St~ontiThu in
Concen~~ations
the Continental Shield •
Rb ~ ~
.€,r x %
Roclt ~
% Wt.
GE'ancdioz:-ite
59.2
122
4-40
8.1
88
500
1
40
31.5
32
440
10
139
Shale
0 ..5
149
300
0.7
105
Sandstone
006 .
20
0.4
-
Limestone
0.2
Diorite
Basalt
Rb ppm
Sr -PPffi
<
60
100
72
260
610
<5
1.2
100.1
TOtal
100
90.1
Best es'timate:
Rb
Sr
RbISr
=
90 ppm
::
442 ppm
0.20
-
441.7
~oung Folded Belte.
The young folded belts are assumed to occupy an area
of 42
.
g
lO~.
2
Their average elevation above sea. level
1.25 km with the Hoho at a depth of 37 laD below sea level.
The prism of geosynclinal
sediments is est~ated to extend
to a depth of 5 km (5.5 if porespaces
are included)
and 1s
~haught to include 40%of igneous rocks. of granodioritic::
composition.
The volume of sediments
its mass is 340 x 1015 tons.
is
therefore
126 x lO~<m3 and
The sediments consist of
1a
17605 x 1015 tons
(52") shale,
4401
2"
1015 'tons (13%)
sandstone, 74.7 x 1015 tons (2~) limestone,
(5"" graY'"Jacke,20.4 x 1015 tons
10
15
17x 1015 ~onB
(6%) anaesite and 6.8 2t
tons (2%) rhyolite.
The total thickness of the igneous rO~te below the
6
3
sedimen~s is 32.8 km giving a volth~ of 1370 x 10 km •
To this
must be added 84 x lO~an3 of igneous roclts intruded
into the sedimsnta:y rocks.
lO~3.
The ~n
The total
1s theZ'eforee 1454
)t
mass of igneous rocks is composed of
9ranod1o~ite, diorite and basalt in the proportions
8 47
0
a 1
I
2.85 or, 1n te~s of volume, 9.33 x lO~~3,
111.3 x lO~Km3 and 316 x l06km3•
9ranodiori~a is 1017 x l06km3•
ties (see p. 121
The total voluma of
Taking app~opriate dena1-
) the mass distribution is as follows:
2750 x 1015 tons granodiorite, 317 x 1015 tons of diorite
and .948 x 1015 tons of basalt.
The total
igneous rocks is 4015 x 1015 ta~s.
igneous and sedimentary
to/eight of the
The combined mass of
rocks is 4355 x 1015 ~onB.
Table
of Rubidium and Strontium in
the Young Folded Belt.
~L.8 Concent~atione
~
Ss: ppm
Fob ppm
Sr x %
~t ~
100
100
77
277
~oclt TYPe
% t~7t.
Granodiorite
63.1
122
440
Diorit.e
7.3
88
500
6.4
36.5
Basalt
21.8
32
440
7
95.7
Shale
4.5
149
300
6.7
1305
Sandstone
100
60
0,,6
0.2
Limast;one
107
Graywacke
004
SS
500
0.4
2.0
Andesite
005
88
500
0.4
2.5
Rhyo11'te
0.2
196
197
0.4
0.4
98.9
438.2
Total
<
<:S
20
610
10.4
10001
Best eatiw.ate:
Rb
Sr
Rb/sr
=-
99
=
0.23
ppm
= 438
ppm
Suboceanic Region
This- is the region of the continental
slopes
occupying
platforms
and
an area of 93 x lOGtan2• The average depth
of water 1s 1.75 lan, tho sediments are 4 km (5 km including
pore spaces)
thick follc\"Jed by 11 'km of igneous rocks.
The
Moho is about 18 km below sea level.
The sed1men~s consist of two typesl
mente which ai:e 252 :c 10~3
t~pela91c
in volume and shelf
sed1~
sediments
\'lh1ch occupy 120 x lO~~3 ~
T'ne composition. of the
is approximately that of the young folded belts.
lattaX'
The mass
of the shelf sediments is 324 x 1015 tons and they consist
accordingly of 168.5 x 1015 tons of shale; 42 x 1015 tons of
sands~one. 11 x 1015 tons of limestone, 16.2 x 1015 ~onB of
graywacke, 19.4 x 1015 tens of andesi~e and 6.5 x 1015 tons
of rhyoli~e.
'l'he hemipelagic
sediments amount.to 680 x 10
15
tons and
consist of 519 x l015.~ona of ~erriganous mud, 129.5 x 1015
tons of corcal mud and 32.4 x 1015 tons of volcanic
mud.
In
the calcula~ions shale is substituted for terrigsnous mud,
91o~ger1na
ooze for coral mud and andesite for the volcanics.
The igneous rocks occupy a volume of 1025 x lO~3
areccmposed of 372 xlO~3
of diorite, 186 x 10~l3
tholeei~ic'basalt and 465 x lO~an3 of olivine basalto
and
of
The
masses of these types of igneous rock are lOGO x 1015 tons
of diorite, 530 x 1015 tons of tholee1t1c basal~ and 1325
x 1015 tons of olivine basalt.
The total mass of
igneous rocks is 2915 x 1015 tons.
rocks in the suboceanic region
js
the
The weight of all
3919 x 1015 1:ons.
the
-126-
Table
Concentrations
2.9
of nubidiuM and Strontium
the SUboceanic
%
100
Rb x
Rock
~me
% w'tos
~b Ppm
in
Region
Sr ppm
x %
Sg:
100
Diorite
27.1
88
500
23.8
135.5
Thol.
13.5
32
440
4.3
59.3
33.8
18
440
6.1
Shale
4.3
149
300
6.4
12.9
Sandstone
1.1
60
0.7
0.2
Limestone
1.8
<S
610
GX"a~lacke
0.4
88
500
0.4
2.0
}\nde8~te
0.5
8S
500
0.4
2.5
Rhyolite
0.2
196
197
0.4
0.4
13.2
149
300
19.7
39.6
Coral mud
3.3
10
800
0.3
26.4
Volcanic mud
0.8
88
500
0.7
4.0
63.2
442.8
Basal t
01. Basalt
Terri 9. mud
Totals
<
11.0
100.0
Best estimatet
Rb
Sr
Rb/Sr
yolcanic
20
- 63
= 443
149
ppm
ppm
= 0.14
Islands.
This region occupies the remaining 2 x lO~tm2, rises
0.5 km above sea level and con~1sts
4.5 km of tholeeitic
basalt
of 4 km of andesite,
and 6 km of olivine
basalt.
-127-
The Moho is
14 km below sea levelo
The volumes of the diffexen~ ~ock types are:
a
x lO~3
of anaesi~e, 9 x lO~Jm3 of thcleeite and 12 x l06km3 of
olivine basalt.
The total volume is 29 x lO~tm3.
andesite 22.8 x 1015 tons#
tribution of massas is as followss
tholeeite
15
27 x 10
tons
6
olivine
The d1s-
36 x 1015 tons, totalling
85.8 x 1015 tons.
Table 2.10
Concentrations of Rvbid1um and StrontiUm in
Ocsanic Islands
Rb x ~
Roclt
~3
% t~t.
Rbppm
Sf.' 'P-Pm
Sr x~
100
100
Andesite
26.6
8a
500
23.4
133
. Tholee1te
31.5
32
440
10.1
138.5
Olivine Basalt 42.0
18
44-0
7.6
Total
41.1
100.1
Best estima'tel
Rb
Sr
Rb/Sr
....
-
:.
185
45605
41 ppm
457 PPD
0.09
The Crust of the EaX'th.
The weigbt of all
'the rocks in the crust
above the Mohois 23,687 x 1015 t.ons.
of the earth
The sedimentary
rocks
amount to 1701 x 1015 tons (7.17") whereas the igneous rocks
accoun~ for 21,986 x 1015 tons or 92.8% of the total.
Table 2.11
Concent~at1onE of Rubidium and Etrontium in
the Total C&ust
Rb,x~
SZ
x %
100
Region
% Wt ..
Deep Oceans
20.4
20
450
4.8
Cont. Shield
44~3
90.
442
39.9
Young fold
belts
18.4
99
438
18.2
80.5
Sub Oceanic
16.5
63
443
10.4
10.9.
0.4
41
45.7
0.2
1.8
73.5
440.8
Vole. Islands
Total
Ilb ppm
Sr ppm
100
100.0
Best estimate,
Rb
SIr:
RbIsX'
--
91.6
196
7~ ppm
441 ppm
0.17
In addi~1on to the Rb/Sr ratio for the entire crust
values of this ratio were also calculated
environments.
for certain restr1c~ed
The value of 0.17 obtained for the whole crust
includes the basalts and calcareous oozes of the deep sea
region which in fact is not accessible and 1s not involved
in geological processes.
Therefore it is more realistic
to exclude the deep sea environment
of the
and to accept the value
Rblsr ratio for the continental crust as most repre-
sentat1ve.
The results of these additional calculations a~e
tabulated in Table 2.12.
Table 2.12
Concen~ra~iona of Rubidium and Stron~ium in
Various Par~s of the Crust
Geological Environment
~
Total Crust above Moho
ppm
SZ' PPnl
Rb/s~
74
441
0.17
.87
442
0.20
Sediments in young fold belts.
100
351
0.29
Sediments in sub oceanic regions
114
388
0.29
shields
88
229
0.39
5S
660
0.08
90
443
0.20
Crust only~
Continental
Sediments on continental
Deep sea sediments
Igneous rocks in continental
shields
'* Excluding deep oceanic and volcani~ islands region.
The 1tb/Sr ratio of the continental
that
of ~e
sediments
as 1s that of ~e
and slopes.
continental
in young folded mountains is
sediments
0.29
on the continental mar91ns
The value of the Rb/sr ratio for the entire
crust is lowered by inclusion
assumed to exist
pr~arily
crust: is 0.20,
at the base of the CNst.
of basaltic rO~ts
Because we are
concerned w1~h the upper parts of the con~nental
crust, a more realistic estimate would place the value of
the "effective" Rb/Sr ratio of the crust between 0.20 and
0029 at about 0.25.
Estimates of ~le concentrations
tium have baen i made ln recent
years
of ~Ubidium and at~cnby Turelt1an and Kulp
(1956~ ~~rstman (1957)and Gast (1960) on the basis of new
analytical results.
Previous estimates of crus~al abundances
of the elements ware compiled by Ple1scher
(1953).
Almost
all of the latter ove~eatimated the abundance of rubidium
while underestimating
crustal RbiSX'
magnitude.
As a result the
ratios are high by as muchas an order of
Goldschmidt
value of 2.07.
1.03.
that of strontium.
(1937t for example, suggested a
Rankama and Bahama (1950) still reported
Even Vinogradov
(1956) arrived at. RbISr - 0.8.
These high estimates led to the eugg0s~ion by Wickman
~at
(1948)
sr87;sr86 ratios in limeatonscould be used for age
determination pu~ses.
Summary and Conclusions.
Average concentrations
various
types
of igneous
of rubidium and strontium in
and sedimentary
t'CCks were com-
plied from the most reliable analyses pres~ntly available
The zesulte obtained here agree with
1n the literature.
those
just
published
are more complete
by 'l'ure1d.an and Wedepohl (1961) but
and thus
judged to be more representative.
n brief summary of the results is given in Table 20130
Table 2.13
Concentrations of Rubidium and StrontiQ~ in
Ignecus and Sedimentary Rocks
Rb ~pm
lRoclt Type
Rbls.Z"
Sr ppm
Gran1-ce
196
197
1.0
Granodiorite
122
440
0.28
Diorite and Andesite
88
500
0.18
Gabbro and Basalt
32
440
0.07
Olivine Basalt
18
440
0.04
149
0.05
Eclogite
6.9
Chondrites
3.17
10.6
149
300
sandstone
60
< 20
Limestone
<.5
610
Shale
These values were used to calculate
0.30
0.50
""'3
< 0.•008
average concentrations
of rubidium. and atront1u..ro in various parts of the earthOs
crust
according to POldervaartOs model.
of the results
investigators
A recapitulation
and a comparison to estimates
appears in Table 2.14.
by earlier
Table 2 14
0
The Concent~ations of RUbidium and StrontiUM
in the Crust
Reference
This author
74
44:1
0.17
87
442
0.20 Continental
Crust
100
351
0.29
Geosynclinal sed1men~
114
388
0.29
Shelf sediments
Turek1an & Kulp,
1956.
450
crust. above r~~h.o
Basalt & granodiorite.
= 0.27
Horstman, 1957. 120
Gast, 1960.
Bntirs
74
Average igneous rock
450
0.16
Baaaltsgranodior1ta
'!'hepZ'sferxoed value for the RbISr ratio of ~he upper
part of the continental
crust 1s 0.25.
~ lnl
_
Chap~er:
--..-... - - .---._-_. -~3
.•..
THE ISOTOPIC COf4.POSIT!ON OF STRO~"TIYM.
IN crBE CRUST OF TIm EP,RTri
The best geochemical
evidence
available
at the p~esent
tAms leads to the conclusion" that the rocks of the continental c~ust have a Rb/sr ratio of approximately
the otber hand,
basal~s
the isotopic
of sub-crustal
composition
origin demands
00250
of s~rontium
On
in
a Rb/Sr ratio of the
magmatic source regions in the upper mantle of about 0.040.
Because
the ratio sr87/sr86 is a function
of ~he age and ~be
Rb/Sr ratio of the environment, i~ is expected that average
"
crustal
strontium
has a significantly
than mantle-strontium.
higher
Sr
87
/srBG ~atio
The actual value of this ratio depends
on the average age of the crust and its Rbis);' ratio.
range of values
great
variety
is large because the crust is c~pcsed
of a
of rock tYBes of d1ffeX'ent ayes \'ihose RbISr
ra~ios vary through several orders of magnitude
Table :a.2).
The
In spite
(Chapter 2,
of 'this inhomogeneity meaningful
age values can be obtained by analyzing
those geological environments
aver-
the strontium "in
which are composed of or con-
geosynclinal basinsG
Othe~ such envirOi~nts
ate meta-
morphic sedimentary rocks and para-gneisses# glacial till
and river water
o
Because. geosynclinal
generally subjected to metcmo~hic
sediments a~e
processes du~1ng
orogenies and may become Mg~anitized~ as a result~ the
.isotopic co~oosition .of ths.stron~ium in this particular
environment is oc~st meaningful.
In the following sections available analyses of 'the
isotopic composition
of strontium in chemical reagents.
sea water and a variety
of rocks will b-~ ~evie~~edin
order to arrive at the best est1ma~e for the value of the
sr87;srS6 ratio in ~h~ czus~.
The Xsot,<mic cam~G~ion
of Stroni;ium
Chemical. ~eaaents eU-tO in
The definitive determination
sitton
of.strontium
strontium of
99oS~
95~an
in
Water
ft
of ~he isotopic compo-
was made by tiler (1938) using .matall1c
purity marketed by Eimer and [aend.
His measurements of the abundances of the non-radiOgenic
isotopes have remained unchallenged
since that time.
N1eros
value for the ratio sx87/sr86 ~as 0.712.
1\ldrich E!t ale
(1953) and Herzog et
repeated Nier's measurements
al •. (1953) each
on a strontium carbonate
almost
iden'tical
in Table
3.1.
strontium
xesul ts'..,
l~
Slb1:tmax-y
of 'the data
en,,;J..Eonmeni: frem \.ihich the
The geological
in 'ths EimaJ:and Amendzeagents
never bean established
t'11ith
appeaA:s
certainty.
~~asder1 ved has
'the ccmpO\nyis no
longer in business.
Tabie 381
Isotopic composition of" Str~nt1um in Ch~miQ~l
~eagents
87/86
84L88
~LS8'
Nie~,1938, 0.712 Osl194
p. 277.
:t .007 t:. 0012
Ald~!ch at al.Q.711
:t
1953, p. 458.
0.0068
:!:. .00014
0.1195
0.0067
.0004 ..~ .0003
~ 000005
Herzog e~ al 0.712 0.1196
Remarks
s~ m9tal
99.9% puxe
Eims&' and 1lmend.
srCC'3 Eimer & A...~nd
average of six analY8es
#
o
Oe0010
o
1953, p. 462.
Sra? ISr
Schumacher,
1956, po 21~.
Tats work.
=
0.0703
r 0.0002
S&,C03,"Gen~Chemo,
c.P.,
0.712
Ocl195
:!: O.0003:tOe0002
0.0066
::t 0.0001
let. 10
.S&"C03~ Eimer:
& P~ndfl
lot 492327, ave~age of
eight analyses in nine
months.
Errors
aX'S"'the si:anC!ard deviations
of 'the
10000.
It is evident fr!CJm Table 3.1 tha't thaprec1s1on
of the
detezminatione has imp~oved steadily but that N1eroe orig-
inal values are confi~ed by all invest1gatozse.
precise analyses are those reported hareo
The mos~
of the
1eo~@p1c cc~po3i~iouof st~onti~~ in ocem1 wa~ex
=
seem to indicate that it too has a ~a~io of s~a7/sr86
stront~ ..wa
as
an adequate
of croa1:al
sample
s~goon't1u..?Q
and
to conclude that ~he sr87/sr86 ~atio in the ent1ge ccntinental crust has a,value of 0.712.
However, it gives meaningful
, mateg-1al1s B'trongly
age values only 'When the
enriched in
value of tl1S initial abundance
Table
3.:2
Isotopi~
87186
Author
Aldrich and
~11s value has bean
Composition
sr87 so that the exact
of Bra? is not 1mpcr~ant.
of Sea l'ia~eE" Stg-ontiu..va
86Le.,E~
0.712
0.1196
0.711
0.1201
sea \tJater
lbrzog, 195a~
Barzog at
al., 1954~!.
~lald
at
0.712 0.1189
Pinson et
al., 1957.
Z 00002 :to.0003
1782
0,
Gast, 1960.
~Referred
saa water
sea ~at:e:r
0.718 0.1195
:to.003 :t 0.0004
al., 1956.
po
0.0067
0.0061
:to.OOOl
Oceanic surface
wa'ter. 66018 oW.
39001 N
0.112
.:to.002
to by Pinson at al., 1957, p. 17820
It can easily DS demons~zat@d that a value of 0.112
fo~ ~11eavezage crustal s~67/s~B6 xa~io is incompa~ib10
with an average iib/sx- ~atio of O.25~
If -cheaverage agC)
of the crust is 2 billion years and its s~87/sr86 ratio
at thm1: tirn~ 'Was0.704,
the valuC3 of tbis
would 'be 0.725.
~veg'5ga
If the
ra'cio to-day
s~e7/sx86ratio 1:oday is
0.112 and the ava~ag@ Rb/SL ratiofoz ~he C1~et is 00250
the age of the crust w~uld have to be about 600 million
years.
This is cleaxly not so.
Calculations of this
nature indicate very s~~ongly tllat.the
ratio
czustal sr87/sr86
must be 9~ea:ter 1:'han0.112 .. If this is tile case,
then the p~oblem arises that the isotopic campos1~ion of
saa wateg strontium
is not
in equ11ibrilli~ wi~
crustal
stE"ontiumo
Whe~er
thiS appa~ent aiscEepancy
cannot be decided at this
representative data.
evidence
is real or not
time because of 'the laclt of
If it is r0al, it could be taken as
that much of .tl1e.strontium in solution
oceans is ofsub-crus~al,
volcanic o~1g1n.
in 'the
Because rubid-
ium is enriched in the micas which are not affected by
chemical ~eathe%1ng to any great extentc
~at
it is possible
ordinary waa~!e~ing processes on the continents neve~
If ~is
i:ru~1 much of the zadiogen1c s~87
is
continental~ocks
in
existing
may never enter ~he oceans but is imme-
dia~ely trapped in sedimentary basinso
~le
Rb/Sr ratio of
sea water itself is too l~~ .to develop any radiogenic Sr87
of its own.
An
\
(See Chapter 2.)
..
altez:na'tive explanation is to postulatei:ha't
sr87isr86
ratio
in sea. \'later 15 ..v~~j.~le
'the
depending on tbe
natuze and age of -the rocits in tbe nearest: lamd-mass or
."to
1n the source of the ocean water'.
In tbis case a more
value of the srS7/srS6 ratio for the en~ire
repre~entatlve
ocean may \-Jell be higher
than O.712 and t.he discrepancy
may disappear.
A c:1Ucal
.3.2
sh01l}s
inspection
that the isotopic
not be as uniform
cf
t.he da1;ap:resranted in Tabla
compos1tion of sea water may
as it seems.
Whenthe sr:87/srSG ratios
aX'snormalized to sreGIsX'es.,;;;;0.1194', the corrected values
range from 0.7097 (Pinson at al., 1957) to 0.7145 (uer2og
et
at., 1954). The s~87/sra6 ratio (0.118) reported~bY
Ewald et al."
1956, :1s suspect because their
o1:her ma'terials
evidence
are unreasonable.
resul~s for
There is 'therefore
soma
in suppor~ of tbe hypctha~16 ,that.geographic
variations in the isotopic composition
of sea water-strontium
for ~e
future.
Only a faw dete~na~!ona
of strontium
of th3 isotopic composi~ions ,
in rocks ha.ve been repo:tted.
in the literat.ure.
Gaat (1960) analyzed ten granitic zacks ran~1ng in age from
200 to 9~aater than 2650 tUlllion years and found sr87/sr86
..
:atioB ranging fram O.720tc
rrean of ttle :Rb/Sr ratios
average age 1s at least
1.003, averag1nq'O.830.
The
for 'these X'ocks is 1.64 and theix;
1750 million
years'.
On the other
band four limestones analyzed by Gast (1960) show a variation from 0.704 to 0.113.
Ewald e~ ale (1956) :epoxted
sx:87/sre6 ratios fo: stroni:1anites,
s'tonea
celestites and lime-
;'Jh1ch xoange frOm a low of O.692~ O~;002 for
a
Cambrian l1mas1:one 'to a high Qf O.710:t. 0.002 for an 'Upper
Cretaceous s'tront1an1te~
The .low value is almos1: certainly
in Grror.
It is clear that existing data are not adequate
define'
~e
c:ompoa1t:lon of crus~al
merely to demons~ra~
s1:rontlnm but serve
the extreme varia.tions
'l'he best estimate must therefore
reasonable ~ge for the continents
to
which exist.
be made by asswning a
and':calculating
the
An upp,ego11m! t 'to 'the abundance of
5r87
can be set
by assum1ng that the crust is 4.5 billion years old and
has had a tlb/sr ratio
of 0.25 throU9~Qut ~his timeo
Tal<1ng
the initial sra7/sr86 ratio as 0.7004 (Achondr1tesPasamontso
Gast, 1960), the preBen~ sr~7/sr86
ra~10 should
be 0.748 •
.
.
It 1s hlghly pxobable
thai: the coni;inen1:al masses
are youngeX'
'than 4.5 billion. yea:r and the ave'rage Sr87/sr~6 ratio sh~uld
therefoX'e be less.thal'l'O~748.
1\
lower 11m!t. is obtained wi. th the assump't1on that
the
age of the
continents is only 1 billion years and that the
..
initial ratio was 0.706.
mate of ~he
~11s value is a reasonable es~1-
sr87/sra~ ga~io of ~be upper man~le 1 billion
years ago which has a Pb/Sr ratio o~ 0.04 and a prGsGn~
value fox the sr87jsr86 ratio of 0.109.
t.1onsthe present
The possible
~e
sza7/srS6
r~ss
With these assump-
ra1:10 in the crust 18 0.717.
foZ" the !}Yara9~ Sr87/srSu
ra.tio
in
contin~ntal masse,sis t'herefor~ from O~717to 0.748.
Gas~ (1960)
used. an
initial, ratiocf
0.714;
a RbISr ratio
of 0.33 and an average age of 2 l>1111c;»nyesrs'to propose
'that. 'the pres~n1:Sra?/sr86 ratio of 'the silicic
O.742~
crust 1s
-141Perhaps the moat meaningful
culating the average sr87/sr86
blage of sedimentary
estimate can be made by cal-
ratio of a geosynclinal
and volcanic rocks.
of such a geosynclinal
assemblage
assem-
The eomposi~ion
is approximated
by the
proportions
of sedimen~s and volcanics in POldervaartOs
sedimentary
rocks of young fOldGd' belts (See Chapter 2).
The calculations
environment
Table 3.3
leading to the final estimate in such an
are summarized in Table 3.3.
The sr87/sr86 Ratio in a HYPothetical
Assemblage.
Wi:.." x Sr
Rock Type wt.% Sr.ppm
100
S~
Shale
52
300
156
44.3
Sandst.one
13
< 20
,3
Limestone.
22
610
Graywacke
5
~ndes1te
Rhyolite
sr87/sr86
Geosynclinal
87/86 x Srtb
100
O.733tz
0.324
0.9
0.733
134
38.1
0.712
0.007
0.271
500
25
7.1
0.708
0.050
6
500
30
8.5
0.708
0.060
2
197
4
1.1
0.708
0.008
0.720
352 100.0
o Pure shale and sands~one derived from wea~ber1n9 of
granodiorite 2 billion years in age, RbISr
0.29,
TOtals
(sr87/sr86)o
=
=
0.708.
The sr87/sr86 ratio of such an assemblage
approximately 0.720.
is therefore
'this is considered to be a reasonable
estima~e of the initial szS7/s~86 &atio of a pazagneis6
tion"of gsosynclinal
The isotopic
sediments.
compositions
of stZ'ontium in two com-
posl~es of ~al~ozo1c shale from the east and west coa8~S
of No:rth J.UDezo1ca were determined as
v10us estimates.
.:JUlian "reiGS
Dennen.
'l'"'necompos11:es
check on tl1e pre,.
px-epared
\t1SX'0
and were made available
All psrtin(l9nt analytical
a
by ~ •
by Professor
data
W'. H.
are campi-led in
'J:able 3.4.
The average value of the corrected
for the t.wo shale cOIGposi'tes
sr87/sr86 ratio
1s O.721St 0.001.
This
is remarkably close agream9n~ wi~h ~he predicted value
I
of 0.720.
It
should be borne in mind 'that these are no~
samples of pure shale but coni;a1n calcium carbonate alld
volcanic mateZ'ial.
They
'therefore resemble i:he average
geosynclinal sediment mo:rethan tbe pure sh'ale.
other two analyses
completeness.
Schnetzler
is
The
are included here for the sake of
The sandy clay. analyzed by Pinson and
clOSG
to the ahale composites.
e
m
e·
r.
~
ro
€I)
ro
....
0
U
~
~.
-!J
i4
!
to
~
~
...
&
0
Q2
po't3
e!-S
m
e,
U
ro
0
0
to
M
0
~
M
to
tU
C~
0
m
J!.
(J
ij)
a:
~
k
t>1
~
«JfI4
~
~
Td
~
~
0
.0\
0
\0
<'
\D
\0
0
0
trJ
fj
~~
~
Q..4
0
(f1
•
cG
r:
i en
CJ
&:
~
0
0
~
~
•
0
0\
~
~
&on
\,0
0
\0
0
0
0
•
•
,
c
.,e
~
CO
~
0
•
~
t
•
ttl
P)
...~en;
~
v-1
•
0
Ol
0\
...
.-t
0
J.&
C
M
0
...a
to
N
0'\
rs4
cat
Q\
P-I
.a.J
..
c:
0
0
...a
..
lR
o r\1
ew ~
.eJ
0
~
0
~fJ
~
\0
\0
N
N
0
N
~
~
l'
0)
"at#
~
•
•
0\
tn
tn
"....,
po(
N
,CO
I'
0
•
fD4
0\
....
0
Q,
i'
-
0
0
CJ
U)
\0
.0
..-f
~
r-..
~
.e.J
CO
0
m
H
~
(U
....
ic...
~
~
N
C"'"
t")
•
•
....CO
\0
e-V
CO
03
r-•
,•• 1
N
.r--
•
'.:I
...0
.s
0
.... At
n1
~
~ u
~~
~(J)
...OJ
'-
N
+'
(l)
g
fJ)
(lJ
[i
o&J
I
k~
Q)
~~
en
as
<11
-rot
G)
>to
'0 :>t
t')
w
r:::
a~
CJ
~
'
'5
~
'8
((J
c
~
• c..
0\
OJ
•
~ • ..l\lI
,.,
pot
cP2
,.,tU
tf
•
C")
~
0
~1
0
CD
~
roe
~
U\
CO
M
~
~
N
...,
(t)
~
0\
0
~
9:4'
s::
.t
Oc
~
R0paated measu~am~nts by save~al invest1ga~ors seem t~
1ndicat~ ~a~ ~ha sr67/sr86 ratios of stront11Im carbonate
reagent
(Eimer .and Aiuand) al'ld saa .'Watez-stx-ontium
tical a~ O.712~
It has become customary
are iden-
in age de~exminat1on
\40rk using ~he Rb-Sr m{?thod to assume a crustal
average
sr87/sr86 ratio of 0.712 on the grounds that the st~ontium
in the oceans is an adequate sample of strontiu.'11in the
crust.
The
~/sr ratio of the c~uot and its p~obable age
make a higher value more likely.
to "a predicted
r~ge
0.117 to 0.748.
E,t'trem3' asswnpt:1ons
for the average Br81/sx86
14aldng realistic
assumptions
si~lon and types of s~ronti~~ present
obtained for
rat10 of
of the COMpo~
a value'of
a geosync11n~1assemblage.
0.720 is
!fBasu~ements of
the.sr87/sr86
rat.io of two composites. of'palaozo1c
from
and "\.fesot coaatsof
the
east
0.7215 thus conf1mdnq
shalas
A'OOz-1ca avezoage
the earlier estimate.
The beat information
crUstal
Korth
lead
noW available points to an average
sx87/sr86 rat1.o of "about
O.72S:tOoOOS.
sive study is planned to confi:m this estimate.
An exten-
Intrcduci:ion.
'
All determinations
of the concentrations
of rubidiUm
and-stx:oni:ium were made by tbe mei:hod of isotope dilution
, (Webster. 1960, 'p.203).
of
The method in\'olves
the -addition
a known amount of "spike" to a known welgl1t of the
sample andtha
- isot.ope
ratios
subsequent
measurement
on a mass' spectromet.er.
a solui=ion of the element
of the resulting
Thea spike " is
CO
to be analyzed w'hose isotopic
campos1~1on baa been greatly altered by enrichment
one of th~.1sotopes
of this element.
The procedures
used in 'the preparation
Qf rock'
samples for~alys1s are identical to those given b~
Hart: (1960, p.182)
dried and poWdered
0
Briefly ..' a knO't!Jn
weight of the
rock sample is s~1ked and then
digested in '10;1 mixture of hydrofl~oric acid and
sulfuric
~1d Jon-a large Pi: crucible on a bo1-1ing
water bath.
of
Aft-er the rock is digested t:he hydro-
flu@ric acid is d~iven off by evapo~a~ion and the zesi~
due is disEolved in abou~ 25 ml of 2N vycor-d1stilled
hyd~cCbloric
ae~d.
Rub1di~~ and strontium are separated.
fro~ eaoh o~her and most of the other elemen~e by passing tbe solution through a cat1onexcb~nge
(DO~x
50, 300 mesh, l~
progress
column
cross-linked resin).
The
of t.'he Rb ions in the column,is men!'tored by
a Pt-wire flame tee~o
Strontium is detected by use of
a radioactive sr85 tracer which 1s added to the solution before
it i's pui; on the col~.
'llle strontium
and rubidium frae~1ons are evapo~ated ~o dryness,
dissolved in a small amount of demineralized wa~er
and stored in clean 1 oz. pOlyethylene
bottles until
they can be run on 'the' mass spectrometer.
Strontium
samples are placed on ~he filamen~ as strontium oxalate
'tJh1chis conve~ted 'to
t:he
me~t. briefly to ~ed heat.
oxide by heating the fila-
RUbidium samples are con-
verted ~o nitrates before being put on the filament.
/19 a rule from 42 to 54 scan's were recozded in "each
analysis •.
The measurement of the desired
a standazd ev1at.lon error
isotope
ratio
of 1;he mean of. less than
has
Systemai:ic
Oo2<',bo
errors
caused by contemJination
s~~ple during the che~cal
using vycor-distilled
alized watero
of ~he
precessing were reduced by
hydrcchlo~ic
acid and deminer-
The amount of contamination
was deter-
mined by_ making a ~otal of four blank analyses thgough~ .
.out the course
of tIle investigation
~1'f1eresults a.re
e
discussed in moxe detail on page I60a
for rubidium
(O~061~#I'S) and strontium
. were applied to all
Blank corzactions
(Oo249/",#"~)
analyses.
One of the advantages of the isotope dilution
technique is that after the spike and t.he noxmal Glemen~e are thoroughly mdxed quantitative
unnecessary.
Provided the isotopes
x~covery is
have equilibrated,
any part of tbe solution will g1va ~he desired result.
Moreover, the isotopic ratios can be measured with a
precision of 001% pre~is1on standard deviation of ~he
mean, or better
e
Assuming
'that: the
calibrated and contamination
spikes are propeX'ly
is caKefully controlled~
the absolute accuracy of isotop~ dilution analyses can
be high
0
.
Radioactive sr85 is prepazed by irzadi~~n9
.RbCl with 15 Mev deuterons
The
sr8S is fo~e~
sr8S•
in the ~oI.T. cyclotron.
by 'thenuclear reac~ion Rb85(d, 2n)
It decays by It electx-on capture
.half life
to Rb85 ~J!th a
of 6S days and em:1:tsa delayed
O.Sl Mev.
solid
The irradiation
I' ray
of
t.ime is 1 to 2 hours depend-
~n9 on tbe amount of ar8S aesired.
After ir~adiat1o~
the sample is s~ozed in a lead container
'three days to allow short-lived
fo~ ~wo or
activity to decay.
Bas1des the desiged sraS, a number of other isotopes are produced by nuclear reactions affecting ~e
rubidium and 'the chlorine
present
as ltJell. as the impur1ties
such as potassium and sodium.
types of nuclear reac~ions
(d, 2n),
(d, 2p) and (d, 0<.)
can occur:
G
The following
(d, p), (d, n),
'Theproducts of ihes0
reactions either decay rapidly, a%e noble gases or can
be separated
from sr~S by ~ation exchange techniques.
After.the
cooling period the sample is dissolved
in abou~ 20 .ml of 2N vycor-dist111ed
hydrochlo~ic
filt~red, and put on a clean cation exchange
It
is advisable
to keep the column inside
acid,
column.
a fume hood
and to use lead bricks.~o pro~ect the operator.
sample is e~uted in the normal fashion using 2N
The
hyd~ochloric acid., The rubidiu~ fzacticn is collec~ed
and s:t,ored in a lead ccnt.~ ..ner ~cause
it contains
1800 day,Rb~~ p~aduced by ,Rb8S(d, p) Rb86.
The fzaction
containing sr8~ is easily located by its activity.
It
is evaporated to dryness, zed!ssolved and ~aased througb
the column a second tima.
tium'frac'tion
, :polyethylene
is
diluted
bot~le
~e
final concentrated
wi'th 2N Hel
t"1l1ich is
'CO
fill
stron-
a 500 ml
~,ept in a metal conta1neX'•
.O~ly, 2 or 3 milliliters of ~his solution axe ,added per
sample to g1vG an activity
of ~ 15 cts/mj.n which is
easily detected by a Geiger counte~o
The purity of the 'tracer solution with, respect
to
rubidium and strontium was checked by adding the trace~
'to-the
spike nU.xture used to dei;ezmine blanks.
these contamination
exper1ments,aescr1bed
Since
in detail
on psge160 ~ indicated very l~J levels ,of contamination, sufficient purity of the ~racor was demonstrated.
The small number .of
s!:es
,by 'the mass spec1:rOlOOter
atoms added is
not detectable
0
Calibration of tbe "Spike-, Solutions~
IntrOt.~ucti()n •
Thepzeparation
of the "sp~ke" ,and the "shelf"
.solutions used in the calibration of the "spikesn is a
-ISOjoint ventuze by seve~al.~~mbe~s of the Project s~aff
of the Geochronol0'3,YL3.bo~atogy at 1 1.I. T. ~'U,deg'. the
1
supervision of Professor Wo H. Pinson.
Much detailed
information was given b~ Pinson (1960, p.237).
For
~his zeaaon these ~opics will be considered only briefly
he~e.
~ne actual analy~ical data conce~ned with the
.spike calibration
experiments are t.zeated in more detail
~o preserve them for the record.
The ~spikean used in this investigation
in Rb81and
sra6, r~apeetively.
made using a sr84 spike.
in 'the form of salts
tory.
The salts
aknoWDvolume
correct.ions
are enriched
A few analyses were
They ~~re originally obtained
from ~he Oaut Ridge National
Labora-
weE'e carcefu1.1yweighed and dissolved
of de~neralized
in
water•. Temperature
tiare made as needed.
Before these
solutions can be used for analytical pu~oses
spike
the iso-
topic campo~it1on of the element and its concentration
in the solution must be confimed
with tbe greatest.
accuracy and precision
ErroX's j"n 'the cali-
possible.
bration of the spikes are systematic ezoz:orsand detract
from th~ accuracy of i:he analyses.
A nsh~lf" solution is a solution containing
a known
amount of an element of normal iso~opic campositiono
The concentrations of rubidium and stronti~~ in the Rb81
and ~r86 spikes. respectivelywexe
determined by ieo~ope
dilu't1on uSing such Ctshelf" solutions.
Ths rUbidium shelf solution was prepared by P~ofesso~
w. H. Pinson
by weighing
in a known vol~~
purified Rbcl and dissolving it
of demineralized
water.
A
temperature
corrGction and a corgection for the pressnoa:of 0.52%
~~re applied.
tion:ls
It
The calculated concentration of ~h1e solu-
140.~.9r~l\b/mlo
. 'lWO 1ndepende~~ gravimetric
deteg'CD
mdnations using ru~1dium perchlorate pzecipitatio~ averaged
142.;Ug~ Rb/ml.
This was considered
agreement and the calculated
used in the calibration
The strontium
value
experiments
to be satisfactory
of
14009,)'fgrRb/ml "'Jas
(Pinson, 1960, p.242).
shelf solution was o~19inal1y prepared
by R. P •.Cormier on 3Uly 2. 1956 by weigblng and dissolving
strontium carbonate reagent (Eimer and Amend, lot 492327).
The concentration
of ~his solu~1on is 28~9~sr/ml.
portion of 1~ was diluted by Pxofsssor W. 8
June 24, 1960 to 14~O~9~sr/ml.
0
A
Pinson on
Cormier's solution was
mentB
{(;hapter 5. Table 502).
The isotopic
composition of the rubidium spilte and
concentration of rUbidium in the solution were each
Analytical Data for aba7 Spike Calibration.
Table 4.1
Shelf
spike
~rlmlo
,
Date
85/87
Qual
2/20/60
.01760
Fair
3&10
2/25/61
.01789
Good
lal
1.0158
64007
2/28/61
.01787
Good
1:;1
1.0329
62.30
~veraga
.01179
.000094
ff .::t
E =:t
Data
0
2/26/61
.
85/87
.4320
63,,30
:t 0 ..52
.t;. .82%
.526"
:2 d2-.. )
n(n-I)
E
'eT )( 100 ) t1 ::: rnePl'}
11
The abundances of Rb8S and RbB7 ~~re calculated
the average measured 85/87 ratio as follo'tr~s;
85/87
87/87
Total'
=
=
=
O.01779Z
63.49
0.000094
1.00000 ~ 0.0
1.01179:t 0.000094,
.E
d: O.,009~
from
-E%
F~actional atomic abundance
:t: 0.000092
65 ~ Olt01747
, Z
87 := 0098252
The ~~'k
85
= 000171
= 0.0923.
are therefore identical
experimental
00527
:t. 0.0092
0000009
Ridge analysi.s of this
and 87
;!;;
spike ~Jas
The resul~s obtained at Mo!oTo
to the Oak Ridge analysis within
elt':£"oZ'o
The at.oudc 'i;leight (physical scale)
dium was calculated}disragarding
of the spike-rubi-
the packing
fraction
for
tbe two nuclides.
8S
X
87
X
O.01747Z 0.000092
0096252: OoOOO~9
Total atomic ~~igbt
If Nand
87
a
,8
1.4857t. 0.00782
85.479a t. 0.00783
8609649:= 0.011
of
S are the ~otal numbers
and spike-rubidium,
ro,85/~
=
respectively,
in am1xtura
(0.13%)
atoms of no~al
than the resulting
ratio
of spike and normal rubidium is
equal to
x.
= o. '215M +
O.2785N+
O..0175~
'\\lhere the atomic abundances for
normal rub1diumare
Equation
(1)
O.982SS
the isotopes of
aseumsd to be Rb85
= 0.7215,
Rb87
= O.2785D
(1) is solved for the ratio.! which is t:rans
S
formed into a wei9ht ratio through multiplication
by a
cu
~~'Pffi~1
.. :flu
Atomic: 'W"'eight of s~1ke: Rb
A'tom.:tC \1Jeight
:;
F
:: 85.557
~
--A:.~
, 860965
Th~ t-Jeight ratio
is then solved
for N, the ~Jeight of
normal rubidium in the 'sarnple,b~: substituting
,values for S,
the weight ofsp1ke-Z'ubid11J.ID addedo
In order to minimizae~ro~s
samples in much a way that ~e
it is desirable. to spike
of rubidium,
as/a7
resulting
be ~loBe to un! ty •.. Because basal ts
'can'trat1on~
appropriate
ratio will
cont:C:~iin.
very
a il'~re dilute
lOt~ c:on-
sI>ike was prepared
and was usao in. almost all analyses' gepozted here •
.
,.
'rhe dilute
~87
ep!ltO was prepared
ap1k0 containing
as follm-Js:
63029~$rRblml
10 rol of
were p1pe~ted in~o a
clean volumetric flask and diluted ~o 100 rol with demdne~alized water at 29° Co
A tempsrature correction
both to th.e .10 ml volume a~
corrections
the final
w8smade
solutiono
The
we~e taken 'from the Handbook of Chemistry
P~YSiC8 (~951-1952" po 1791).
Actual volume p1petted at 200 C
_~,
D
J
10
1..002275
:: 9.9773 ml.
and
~mount of Rb delivered
=
This amoun't'\~asdissolved
Pinal
concentration
The concsntxat1on
=
B
631.46~gr$
in -l&~2 ... :: 99.773 ml of
1.00 75
water
6~1~46;U.9!:S.:;: 6. 33 ~j7Rb/ml.
99.173 mt
/.
of this spike solution was checked by an
isotope dilution measurement
solution.
63.29 x 9.9773
"lhe result:
using the nOkTaal rubidium shelf
obtained
was Gc.
581".9?'Ym'~.(ml Wllich is
in satisfactory agreement with ~he calculated value.
Never-
~hsless. the calculated value was prefer~ed.
A further
chec~cwas made by analyzing
the rub1d1~
content of R1292 using both the dilute. and the concentrated
spike.
The results age identical within experimental
Calibration of sraG spike Solutla~.
The 1so~opic composition and the concentra~1on of
strontium 1n the .Sr86 spike solution were determined
triplicate isotope ratio and isotOpe dilutiOn runs.
respectively.
Table 4.2.
'Ehe analytical data are presen1:ea
in
by
com~~~
l)~~rsptopie
Date
. ion,,86L88
87~8
Pair
80014
72
GOod
1=?3765
..
0077
90
Good
12,,4216
.0076
1.4176
12v4168
7/25/60
1.40.02
12 4715
2/27/61
1..4002-
Average
1.4060
-
::t
-E
:t
0
:t. 00275
.0058
0.413%
.
..to.221%
Shelf:a~ike
2/26/61
2/26/61
Qual.,.4!..
10
6/22/60
c:r .
Soans
8!r~8
:t..OOOO9
:tl.16~
sr~PfJl:Imi.
86/88
2:2
1.5110
21.54
. '2:1
0.8537
21 44
281
0.8577
21.,56
6
.~.51
. Z 0.037
:AveX'a~~
.0=-
-
E
)
.-E. - -
t.
O.17~
0-
t1
Shelf solution contained 14.03~~rsr/mlo
.
~le atOK~c \~19ht (physical scale) was calculated
disregaxding
the packing fractions for the different
nuclides:
88/88::
1 ~OOOO::t0.00
87/88:;
1.4060 :t 0.0058
86/88
=
84/88
=
Total
12.42,16:t 0.0275
0.0076 :!:. 0000009
14.8352
t 0.281,
E
a:
O.189~'
Atomic abundance
=
0.06741
:t 0.00013
;t 0.193
87 ':::
0.09471
~ 0.00043
't. 0.455
86
84
t
0'.00243
% 0.290
1:. 0.000006
:! 1.20
88
III
iii
0.83731
0.00051
Atomic weight (phys~cal scale)
=
x 0.06741% 0.00013
S.932oat 0.0114
87 x 0.09477 % 0.00043 • 8.24499:t 0.0374
96 x 0.83730t 0.00243 II 72000780t 0.209
84 x a.OOOSl.:! 0.000006
, 0004284 t 0.000504
S8
TO'tul'
• 86.22771
=
86.228:t
0.213
(0.247%)
The ratio of sr86/sr88 of a mixture of N atoms o~
normal strontium and
. to
S
at:omsof spike strontium 1s equal
\1:
O.,?986N
O.8373S'
J
O.B256N
0.06745
The weight factor \~~ichconver~s the atomic ~atio of N/s
).
to a weight x-atio is
Atow,j.c \I:ei~bj; of ft0zma1Sr
Atomic \ie1ght of spike Sx:
......
::
~
86 ..228Q .
1...
0112
that. the st.rontium in the unltncwn has
The assumption
a "no~al"
composition is usually not strictly tgue for
geological
mate:rla8n.
Normal stron't1um is
sr8'/Sr86
the foll~~in9 isotope ~atios:
sr86/sr8S
= 0.1194
and s~a~/sr8S
=
assumed to 1'1a<'''ia
= 0.712,
0.0068 (N1er, 1938).
Many samples ~nalyzed for ~he purpose of age aetermination
by 'the Rb-Sr method aze enziched
in the Sr87 isotope.
Por bast results it is 'therefo:re desirable
stitute the proper1sotopic'
abundances
in the sample into equation (2).
fogosamples which ere strongly
sr87•
AlIDost all
samples
'to sub-
for the stron~lum
This is part1Cl.l1arly
enzoiched in radiog~n1c
analyzed hereaiffered
very s11ghtly from eJnormal~ strontium ~d
only
all concentra-
~1ons could therefore safely.be calculated using the .
equation as given above •
. 84
Calibration of the Sr . SRike •
.I
Only a few analyses
:7"
t;rue
r
\\7ere made ust'ng tb1s8p11te
and
reco%tl in Table 4.30
Table 4.3
Atomic Abunaances'of
Oak Rid99
the Isotopes.
M.I.'!'"
84
.543
.002
.5356
86
.137
.002
.1401
81
0038
.002
.0428
'ss
.262
0003
.2808
The M.l.T. values are averages' of two independent
detexminations.
An ieo~cpe dilution measurement gave
SX'= 19. ?o/i.fr/m1. The calcul&ted value is 19o~.9rsr/ml
indicating
1.0253.
very' good a.greement.
The weight factor 1s
!reciaion o~ Rtiliidiuman~
~t~ontium Analj[~as~
J.
The rep~oducib111ty
of isotope dilution analyses of
rubidium and strontium was detexmdned by making triplicate
analyses of several samples containing
t~ations of the
1:t'1O
different concen-
elements. 1\11systematic errors were
removed as far as possible by ca~eful spike calibra~ion~
and by m~~ing a blank correc~1on to all determinations.
-A
~emperature
correction
not made because it is
Rubidium
to the volume of spike added was
inaignlficant..
C),nd Strontium. Blan~~
The blanks
were dai:e:rm1ned by mixing
of 'fd)87and SrS6 spike in a p~ crucible
i:hen subjected to the eni:ire procedure
prepare
X'oc:ksamples
Compaxable amouni;s of
0
known ar.~nts
The mixture was
o:c'dinarily used.to
for isotope dilution
analysis.
reagen~s were use~ 'throughou't
and
the blanks were put: through an lon exchange colwun which
had been cleaned ~av1ously
in the .customary way.
the resulting isotopic compositions of ~e
Finally
rubidium and
tbe strontium were dei:erm1ned on the mass spectrometer.
The amount of contamina~ion
of each element was calcu-
lat.ed by as~umin9 it. to have'nonual
isotopic compos1tionQ
During the course of this i~vasti9ation four such
rubidium and st?ontium blanks were determined
Rb~r.
srp£
O.173'Cl
0.425
,9'/60
0.0826
2..;75*
11/60
0.0560
0.138
2/51
0.0636
00183
Dai:e
T
(Table 4.4).
"i
'8/60
"
b~cause they ar~ unusually high and above the general
level of the ~thers.
corrf9ctionsare :Rb
The values used to make blank
= O.~67S~$r,
Sr
=
0.249/9Y
The ma9ni~ude'of the blank co~rsc~ions to 0.5 gram
Table 4.5
Ma9n1~ude of RUbidium
ana
Concentrat,ion of Rb & srcorrecUons.
Blank correction
S~
in rock (pmn)
1
10
100
Sample slse
Stron~1um Blank
Rb~
-50
-13.5'
- 5
- 1.35
.S
=
0.5 grams.
- 0.135
made on four saraples.
by ~out1ne procedures
Bach of
'these
s£b."\1plea\t.Jasanalyzed
used in tl1e Geochronology
Laborato~;y
at M.I.T.
Therefore the spread of tho da~a at various
centration
lave].s is a ~ea11st;.1c indication
duc1b111ty
(Tabla 4.6).
~Table 406
Summaryof Triplicate
of the repzooc,"
Rb a.nd Sr Analyses.
Sr p~
394.9';'t,;
402.9
397.1
398.6
:t 2 0
0
:/:.o.
5~"
:t 3.1
~ 0.93%
131.7*11<11
148.3
149.7
149.0
:t 0.7
:t 0.47%
'i: 0.99
:!:.: O. 66S~
lll'
Using concentratl!dRb97
spike (63.2~..9'- 1m!).
t/. USing f3r8~ spike.
G** Spiking in doUbt.
C011c:>
Om1tted from. the average.
(continued)
-163- 'fable 4.6 continued
-,
Saniple
~Yo.
P3111
pyroxene concantr.
Average
,c-
Rb ppm
Sr J:mm
12.7
272.7
13.2
13.0
257.9
254.9
13'.0
' 261.7
E
t 0.147
:f: l.l~
c:r
:t
E.
% 1.96%
0.255
;t 5.6
i: 2.14"
9.6
z' 3.67%
:t:
17.50
0.92
1.41
03111
Garnet concentr.
Average
1.03
21.80
17.70
1012
19.00
Cf
-
1.
B
:t 13.~
rr
z
0.148
0.257
1: 22.9%
E
_
0-=
2.~
Z dfl.
:t
~
~
1.40
7.37%
2.~2.
!: 12.7%
x
)
100
'n(n-I)
por ~he purpose of evaluating
of an individual
a single analysis
the precision error
analysis the standard deviations
«(/) is most applicable.
In general
the precision of rUbidium analyses in material
lngN10 ppm Rb is of the order of ~ 2%.
tion decreases
for
contain-
As the concantra-
to 1 ppm the error increases
rapidly to
material containing
150 ppmsr or more is of the order
of .; 1%, but may be as higll as::t4%. At 'the 20 ppm leyel
.
the .precision appzoach~s t. 15%.
From the evidence 'pgsoo
sented here a conse~vative est~ate
precision erxoor of a single analysis
robidium
and strontium
of ~e
probable
ist 2% for both
whe:ce Rb;? 10 ppm and
sr:; 150
ppm.
It is of interest to noi:e that the rubidium and
strontium concentrations
of R1292 which were made using
..
t~econcen~r&ted
Rb87 spike and the. Sr84 spike, respec~
t1ve~Ytlare in perfect
This gives confidence
. Rb87 spike
agreement \'11:'th the other valusso
in the calibration
and the 8%,86.spike
of the dilute
which \\'ere \lsed on' almOst
.all the other analyses.
The accugacy of rUbid1um analysss is indicated
by
a comparison of the r~sults obtained 'here for. aRbCl
soiut1on prepared by G. R. T111;on:to ~ose of several
other laboratories
(Pinson, 1960. p.244).
was analyzed in triplicate
different'
by Professor
~s
solution
W. H. Pinson using
pgooportlons'of sp11te and shelf solution.
resul~s given here ha~e been.recalcula~eduslng
the
The
la~est calib~a~ion data fox the ROB7 spike solution
T~le
4.1
Analytical Datafor ..Tiltont.s
Shelf Solution.
Spike: shelf
1:1
0.6355 .
69.,41
1.009
68.17
67.69 68.18
68.66
1.263
.1.254
AveragG
Concentration:
6a.79~er/ml.
if = t: 0.36(0.5%)
a- =
t;
0.62(0.9%)
The reproducibility in te~s of tho standa~d deviation
for a single
analysis is Z. 1%. This is a. m1n1mum
"slue
because
these analyses
did not.'include the chemical
cessing
used, fo~, analysis
pro-
of rock G&~ples~
The aver.age of t.he M.l.T. analyses is identical w1thin experimental
erxoor to ~e
Table 4.8 Interlaboratory
resul1:s obtained elsewhere.
Results forT11:ton's.Rubidlum
Shalf Solution
--
It!!JI' Iml ..
Laboratory
~
M.loT.
66 8:t 004
0
Carne91(~,r;.Insti tut.ion
GastD University
Minnesot~ ..
,
of
6705
6805
. Chapt.e&- S.
fgEASUREMEf.\lTOF THE ISO'rOPIC
COf.iPOSITION OF STROIG~UM~
~ntroduet1on •.
The cbemical procedures ~nd instrumental
used in this investigation
techni~es
are not new but were developed
f'
over a pe:e1od of years by members of the ~eoch!:onology
Laboratory
bave
Vag-laus"aspects
81: M.IoT~
been described
in 'the Annual
'as,in the geochemical
literature
of these procedures
Pro~lress
Reports as wel:".
(Hart, 1960, p.169,
:Pinson, 1960, p.237J sexzog et al., 1960, Herzog et al.,
1958, Herzog and Pinson, 1956).
In this chapt:er these
analytlcalt:echniques are briefly summarized foll~
by
a discussion of.measurement precision ,and absolute accura~
ey.
Chemical Procedures
'It
For strontium isotope ra1:io determ1na~ions roek.
samples were ground to a'grain size of less than 250
m1c~onsin ,a steel, percussion mortar.
Approximately
0.5 grams of the powder, which was well mixed by rOlling
it on a sheet of paper, w~s placed in a Pt crucible
digss'ted :i:nabout
2S rols of a 10:~. mixture
and
of:HP and
on a bOilin9-waterba~1n a fume hcod~. ~ilic~
4
.
was volat.ilized as SiP" by a reaction.with Fions and a
4
...
H S0
-
2
.
.
solut1c~ of soluble sulfa~es wa~ obtained (Vincent, 1960,
p.41) .•
'1'he decomposi'tion process Z'equ1red from 3 to 4
hours.
The resiClue:was dissolved
demineralized water.
in about. 50 mls of
"the solution was stirred
clean Teflon stirring. rod, if necessary.
of the. residue.
all
of HF the
almost to dryness.
1Ina~ely 2S.mle of 2N vycor-dist111ed
thus converting
to dissolve
In ordaZ" to remove all traces
water solution was evapora~ed
w11:ha
Approx-
HCl were then added,
the salts to chlorides.
The solution
was'.cooled and f11'tered into a pyrex beaker. for t~mporary
storage.
" Strontium was separated
fx-omthe other elements by
.cat~on e2tchange t:echn:1quea using
12~.cross-linked
eluan't.
~esin and 29 vycor-d1st111ed
The exchange columns ~X'e
successive
,distilled
Dowex. SO, 300 mesh,
samples by duplicate
cleaned
washings
Rei as
between
with 6N vycor-
Bel" followed by 21fHCl or dew.nex-alized water.
Before the solution was put on the column it was filtered
a second time ~o remove p~ecipitatee which usually
.
).
formed on standing (Rei, ~aC12)e
A few mdlliliters
of.a solution contain1~9 radioaciive
Bras
were added
.to give su~fic1ent activity so that the location of
.
'the si:.rontium en the ion exchange column could be
detected
"lith a .Geiger Counter.
was .then levelled
column.by
.
T11etop of the z:esin
. ana the solution
means .of a pipette.
'Was pl,acea on t!-:~e
Care \'Jas taken not 'to
lJ
disturb
the surface
of. the. resin to obt.ain the best
possible
separa~1on of strontium
diuman~
potassium.
The order
and alkaline earths are eluted
Ll, .N-a, K, Rb, Ca, Sr (Conn1er',.
.fraction containing
from calcium,
rub1~
in \tJh!ch the allta11s
.fhOi'D
'the colUmn is
1952, p.7.2).
The
the stron~1um waG collected. in
25 ml po~t1ona 1n 3 t:o 4- pyX'ex beakers which we:r~
'then evaporated 1:0 dryness.
the greatest.
The beakers containing
amount of ~lct1v1ty were selected
residues were d1ssolved1n
and the
a few ~11i11texsof
demin.
,
erallzed water.
This.stron~ium concentrate was ~tored
in a clean 1
polyethylene
OZ ..
bottle
until
it could be
analyzed on.the mass spectrometer.
Whenanalyzing
e'trontiu..1U in basal~s
it
\i8S
usually
all soluble oxalates.
capillary
Next, it was picked up in the
tube' and deposited
in the cent.er of a cl@)an
tantalum filament in the source of the massspectromet.er.
'rhe liquid
was evapora'ted
by passing
a small
current. '(NO.5 amperes) through the filament until
sampla forme(! a small
wh!te cake.
Th~ filament.
the
~emperaC)
ture was raised for an instance ~o red hea~ ~o expel
occluded gases fram the sa~ple and to convert the
o~ala'te1:0
the oxide ..
and/placed
in the tube of the mass. spectrometer
preparation
'.me source was now. re-assembled
in
for the analys1sG
Mass s~ctrCmet%ic Teehn1croes.
The instrument. 1s a 60° sector,
6 inch radius,
solid source, single collector mass spectrcme~er
which t~as built
at N.I.Te
lot employs a magnet: sweeip
and the ion current 16 amplified
ing reed electromet.er
cOZ"porat.ion,
Pasadena,
by
means of a vibrat.-
(Model 30, Applled.Physics
california)
Cl
Samples
were
mounted on a tantalum ribben (0.001 x 0.030" by
Fansteal Metallurgical
co~ra~1on"
Nor~h'Chicago6
IllinoiS} spot welded to posts in 'the source.
Operating
'p~easures ranging
fr~"'l1 3
rom Hg waze obtained,by,means
x
6 to
10....
:l'
5
10-7
of a high capacity mex:cury
d1'ffusion' pump using a large cold ~rap cooled t'.1i th
liquid
nitrogen
coupled'with
Scientific
(i-1 8. Ma~t1n Co." .Evanstcn#\,
Illinois,>"
0
a fore-pump
(Duo-Seal Pumps, W.,M. Welch
Co., Chicago).'
\1ere recorded on a
The ~alts
:Brown Electric Strip Chart. Recorder
(Er~;n Instrument
Co., tiphiladelphia).
After 'the 'sample l1ad been applied to the filament
tbe~source waS returne~to the maeB, spectrometer
bOi:ted into',place.
' To ensure a tight.. seal a
Aluminum,gasket was used .for
each run.
mass .spectrometer was than evacuated.
"measured, by means of.an
and
l'leW
The tube of ,the
Pressures
~re
ion gauge (CJ.lfpe DPA 38 ,Consoli-
.dated. Elect.rodynamics Co., Pasadena, California,
D1st. Prod. corp.).
Whent;he pressure
formerly
had. fallen
.about 2 x 10-5 mm Hg (usually in less ~hanone
t.o
hour) ~e
filament current was turned on and the sample was con,ditlonod ~or 2 ~o 3:hours at.a temper~ture just belOw
..t;hat"at which strontium ion emssion' begins.
ing the sample in this
Condition-
""Jay allows r\.widium conta1lt)ina'tion
to be burned off, gives abetter
operating
vacuum, and
imp~ove9 the aenBitivi~yof ion emission du~ing ~he run.
filamsnt,curxent was ~nc~eased alowl~~
s~le
p~event the
from falling off 'the filamentJuntil
Of strontium
ions began to increase
the peak heights
\fJ6X'eJ
the emission
spontaneously
When
D
great.'enough to be in t}~erange of
1;he 100 (81;87, sr86, srS4) .and 1000 milll~~o;Lt (sr88)
scales of the V.R.E.,
from SO to 100 consecutive
scans
t'}
were reco~ded wltho~t further
changes in 'the. filamen<t
In this 1nves~i9ation an ins~rumen~al precision
'for 'the sr87/sr86 ratio of better than 0.1%was desired.
Experience
.sho~~d tha~' such precision
by recordingbetwean
bfusing
could be achieved
80 and 100 conseQJu'tive
the 100 an4 1000 mv scales on the V.R.Eo
twq'scales are least sensitive
and small irregularities
to hi.gh';.
84: to' 88, is
molecules
lit
(These
~requency noise
in the ion emission.)
The.re~olutlon of.1:he instrumen~,1nthe
mm,8<) •.
scans arid
mass range
adequate at prestSu&"es.' less than 5 x .10-6
higher pressures
causes broadening
i~ overlap of the pe'aks.
collisions of ions with gas
of the ion beam-resulting
The Sr88 peak i'n particular
intezfs~es with the smaller sr81 peak with the ~esult
that the measured values of the sr87/sr86 ratios are
too high.
In this
\'Jork pressures
o~3leas than 2 x 10-6
rom of Hg were prefer&-ed for a reliable
the Sr
87.
ISr
86
measu&"ement of
ratio.
After s~rontium isotope ratio and isotope dilution
runs the filament was cleaned by heating at maximum
tem~rature
until no trace of strontium or rubidium
could be detected at a filament current higher than
that: employed during a run.'
In this
~lay up to six or
eight consecutive samples ~~re run on the same filament
without danga~ of contamination.
It was found to be
safe to interspace strontium iso~cpe dilution and
isotope
ratio, runs although
'this was avoided
as possible in' this project.
as much
After making a 1~b1dium
analysis the filament must be discarded because rubidium is difficult to clean off the filament.
After completion of the run the chart was analyzed
as follows.
pencil
Baselines
'tiara drawn wi1:h a sha11:pNo. 4
and peak height.s were measured to the closest
0.01 inch uSing an engineering
ruler.
The peak
heights ~~re averaged in se~s of six and isotopic
ra~ios ~~ge calculated for each set.
valueS foE:'the entire
ratios
obtained
The final average
run \~re calculated
for all
'the sets.
from t.he
The number of scans.
i~cluded in each set should be even in order ~o remove
the effact.of increasing or decreasing peak haignt:s from
the isotope ratios.
An instrumental
aevia.tion
the form of the standard
culated for the average sr87/sr86
precis10n
error in
of the' mean was cal-
ratio of each run.
This ,erEor was used t;o judge -the qualit.y of the measuremente
It will be discussed
in more. detail
in 'the next
section.
p~scussion of Errors.
In'trcduct1on •
.
.
In the following discussion
bet~en m$asurement pxecis10n
'the absolute ,accuracy.
or
a distinction
reproducibility
The formsr lethe
errors arising from several sources.
is made
and
sum'of randcm
The magnitudes
of
these rand~~ errors in a mass spectrometer cannot be
predici:ed wii:h certainty.
In thissi:udy
the x-eproduc1
b111ty of the sr87/sr86 ratio was dete~lnad from a
number of analyses of the same sample and was e~ressed
Ct
as the standagd deviation for a single analysis calculated,fzam these results.
0-==
~f
2,',
d::'
of a nUiuberof measurements
)
I'J -I
average' is M implies
tbat an, additional
the a8lT~quantity,has
the band M
.Z
The standard deviation)
whose
measurement
of
a 66" probabilit.y of falling inside
0- •
The absolute accuracy 1s. tIle algsbraic sumof all
systematic. errors affecting
a series of measurements.
Again such e~rors arise from many sources and are difficul~/to evaluate
in ~he. lengthy and complex procedu~e
used to dete~ne
isotope ratios. Because the ~rUe
value of the quanti'ty to be measured is usually
no~
'known. lt 1s ,customary t~ analyz9 inter-labora.tory
II
standards
to ensure
'that at least, a certain degree
consistency is maintained.
/
The standard used here is
a S,X'C03 by Eimer and AmendttJhich has previously
been
analyzed by Aldrich et ale (1953) and Herzog et &l~
(1953) .'
The p~~c1sion errox or xeproduciil11ty
measuzoement of the
B-;:87/sr86
of
ratio
of a
1s 1:he s~
of
-seveX'al random errorso
Several of these elrZ"ors, \ih1ch
are listed below, may be systemat.ic for a single measurement but are random for a series of repeated maasurements.
They therefore affec~ the reproducibility
and are included
These ares
in this discumsion w1~ the truly random erxors.
1.
20
Contamination of the sample with variable amounts of
C:normal" or: I'8spikeco stront1wn during chemical process
ing or mass spectrometric ana~y~is.
Variable
effects
evaporation
from
t1on, deflection
't1on of 1cnso
30
of fractionation
the fil~nt,
~y.the magnetic
Pluctua~lonein~s
of isotopes
lD
auring
ioniza~lon, accelera~
analyzer
and collec-
rate of e~esion of.ions from
the filament caused by inadequate temperatuxe cont!:'ol
of the hot filament, chang8~ in. the resistance of
the filament, excessive bulk or near-exbaust:ion of
the sample and other reasonso
4.
High frequency electronic noise as ~el1 as instrumental drift due 'to 'temperature changes, interference
from 'the operation of other electronic equipment,etco
s.: ///Lack of
sufficient resolution of peaks due 'to bJ:oaden1ng of the ion beam as a resul~ of collisions of
ions wi 1:h gas at.emv:; in the mass spectrometer tUbe.
The resolution is also affected when 'the ions are
not mono-energet1c
because of improper alignmen~ of
the fil&~nt, the sample and the slit of the accelerating. p~a'ts •.
6.
Instabill~y of ~he magnetic field and of the accelerating voltage.
Low frequency noise in i:he st;~ength
of the magnetic field results in corresponding
1ns'tab111ty of peak heights •. Var1at:ions in the
accelera'ting.voli:age affect 'the spacing of peaks but
may also affect t:he peak"height.if
such changes occur
just before the recorder reaches the top of a peak.
7.
Uncertainties in drawing baselines and measu~in9
pealt heights with a roler.
Of these sou~ces of errors contamination
of the Ba~ple,
and poor resolution may be systema-
isotopic fractionation
tic for a single run but differ from one analysis to~he
next ~hus affecting the reproducibility.
An
isotopic fractionation
all meaauredsr87/sr86
correction was applied to
ratios on the assumption
that "the
sr86/s~88 ratio is constant and equal to 001194 (Nter,
1938).
Any deviation
from this value was asc~ibed to the
effects of isotopic fractionat1ono
Only one-half of the
correction needed to xeadjust the-sraG/SraS ratio was
applied 1;0 the
sr87/sr86 ratio because "the difference in
'the masses 86 and 87 is
aa
only one-half'
tha.t between 86 and
Por example, 91ven that.
0
s%86jsrSa
s?:87/sx86
=
=
0.1187
0.112
then,
(sr87/sr86)
cOrr
-
0.712
00.1194
=
0.7099
0.11905
"Even though the exact nature of this
tionatlon in ~he mass spectrometer
isotopic
frac-
is not understooQ,
-Xi'2-
lanonnalization
Q
of the sr87/S~86 ratios is justified
the resulting improvement in the precision
and by the fact 'that the mean of several
,standard
(Table
~able 5.1
by
of the data
analyses
is not
5.2).
Xsotop1c composition of S~rot:!tium in Basalt
fX'~
Ki lauea. Hawaii (lR1292)
ES7
No.of
..
86
(87/86~orr 86/88
84/88
scans
Qual.
e7068
.1196
.0010
138
Fair
.067
.7012
.1194
.0063
84
Good
.7090
.054
.7069
.1187
~OO66
84
Good
4) 1/25/61
.7040
.13
.7058
.1200
104
Pair
5) 2/8/61
07091
.073
.7061
.1184
90
Good
Average
.7077
No. Date
87/86
1) 6/1:/60
.7062
0091
2) 8/31/60
~7102
3) 9/3/60
--
.0065
--
:t 0.00114
.0066
.1190
:t 0.00026 :t 0.00033 t 0.00015
:t 0.16%
:t 0.037"
a-
t 0000254
;t 0.00059 :t 0.00074 :!: 0.00029
E
:to 0.36"
~ O.OB~
0=E/'
/
.7066.
~
Z
0.28% t: 2.23%
0.62% ~ 4.45%
'the results in Table 5.1 show that the reproduc1b111t.y
of ~he sr87/sr86 ratio, expressed as the standardd3~1atlan
for a single
analysis.
is improved by about a factor
of
four by the fractionation correc't1on. In th1s set of
measurements a ~eproduc1b111~y of Z 0.0006 (0.08%) has been
achieved for
the
corrected
sr87/sr86
ratio.
The column headed E87/86 givas the inst~umental p~e~
ciaion er:~or of thesr81/srB6
not identical with ~e'
but indicates
Th1~ 'er&"o&"
£s
for eacb run.
rep~oducib11ity of the measurement
only the extent of varia1:ion of truly randam
erro~s affecting the particular
mass spectromstzic
measure-
,mente
The quality' of a run was determined
partly on the
G---.
basis of this instrument precision erro~ of the sr87/sr86
ratloand
partly from oi:her criteria
of
ion emission,
t:he
the run 'and evidence
of excessive
frac-
of scans recorded,
pressure
during
t;1onai:ion.
t)GoOdIll,
'the stability
As a. x:ule me'asurements having an instrument
error of 0.08%
w1th errors
or bei:ter ate of "Gooa" quality.
caFa1r"~ or apoor" on the basis of the other criRuns having an error greater
than 0.25' were considered
~e
Those
between 0.087£ and 0.2% a&"Sjudged to be
terici mentioned above.
discarded
such as the' number
to be "'PoorIt and
were
geneX'ally
or.repea~ed.
xeproduc1b11ity of the s~86/sr8a ratio in Table
5.1 1~t;O.6~ whereas ~bat
ratio 1stO.36~.
the sr87/sr86
of
the u~corrected
sr87/Sz86
This supports tbe earlier assumption th~~
ratio is. subject to only one....
half of the
-ISOisotopic f~actionation effect reco~Qed in the s%66;SrBS
ratio.
The ~eproduc1bility of th~ sr84/sr88 ratio as .
.
.
indicated in Table 5.1 ist4.4S~•
. AccuraCY...
~
The absolu~e accuracy of isotope ratio measurements
is diff1cult to assess.
demonstX'a~e
..consistency
Ir-.
made elsewhere.
The best that' can be done.1s to
of the measurements
For 'this purpose
with ot.hers
'the strontium
of a
S~C03 reagen~ (Elmer and Amend, lot 492327, Co~ier's
shelf ~olut1on) was analyzed at intervals throughout
course of the investigation.
Table 5.2.
~e
the
results are given in
-181-
Table 5.2
No.
Strontium Carbonate Reagent, Eimer and }\.m.end
lot 492327
(81/86)
87/86
Date
86/88
corr
84/88
Qual.
Good
.7114
.7116
.7117
.1200
.1195
.0068
.0066
Good
6/30/60
.7133
.7130
.1193
.0064
C-ood
4
7/20/60
.7133
.7127
.1192
.0062
Good
5
8/21/60
.7136
.7127
.1191
.0069
Good
10/17/60
.7128
.7116
.1190
.0069
Good
12/1/60
.7111
.7102
.1191
.0067
Pair
.0064
Goed
........
Good
.7098
4-
5/3/60
5/15/60
3
1
r#.
6
7
v-
".-1
8
2/13/61
.7083
.7077
.1192
9
2/27/61
.7093
•7123
.1200 .
0.7114
Average ""
-
:!: 0.00064
j;
a-
Z. 0.090%
0.0018
x
:t 0.077"
t:. 0.0016
B
!
"!;
0-
'E
0.25%
0.00055
spread ,than the uncorgected
are .zuns #7 and #8.
1:.
0.0066
0.00016 :C 0.00008
;t 0.134%
:t
1.23%
Z 0.00045 :to.00023
+' 0.38%
0.22%
sr87/sr86
The corrected
0.1194
0.7115
ratios
The values
ra't1os of these two runs differ
of
:t
3.48"
The only
~e
Run #8 is outside
therefore rejeoted.
ana
Sr87/sr86
from 'the mean by 0.8
will occur in a ;normal population
(Dixon
exceptions
correc~ed
and 2.4 (J. Ths probab111:t1es that these or
0.8%, respectively
smaller
have a markedly
ratios.
and whose standard.dev1~'tion.cr
-
lO\«3X'
a-
values
whose mean is 0.7115
= 0.0016
Massey,
are 21.2% and
1957., Table A4 ).
'the cus1:amary 5" confidence
limit and is
with the ~ssion
of run #8 the isotope ratios assume
c-r
average valueSe
the following
r:r
sr87/sr86
-
0.7119
,z 0.0006
, ~ 0.0016
(S,r87 /s~86)
-
007120
Z 0.0003
, Z 0.0009
0.1195
:t
0.0002
, :t 0.0005
0.0066
:t 0.0001
, ~ O~OOO3
corr
--
sr86/sr8a
COlt
sr85/sr88
It is apparent tha~ the average sra7/sr8G rat.io is identical
v-
to the corrected value of this 'ratio.
of the latter
is
Z. 0.0009
or
Oel~.
The results of this, series.of
favoura'hly with those previously
for similar
gatora
The reproducibilit.y
measurements
reported
strontium compounds.
work, is given in Table 5.3 (Also chapter
Tabla ,5.3
Isotopic
compare
by other
1nvesi:1-
A summary of
'this
3. Table 3.1).
composition of St.rontium in Chem1cal
Reagents.
Aut.hor
87/86
86/88
N1ez:, '1938,
O~712
0.1194 0.0068 Sr met~l 99.9~'pu%o,
p.277.
Aldrich,'
Z 0.007
et
af.,1953,
00711
":t 000004
8A/a9 ,Remarks
%0.0012 :to.00014'
E~mer and Amend.
0.1195'
0.0067
:to.0003 %0.0005
SXC03'
Average
Eimer & Amend,'
of
6 analyses.
p.458.
Herzog at
0.712
al.,1953,p.462.
sr87/sr
Schumacher,
0.1196 0.0070 sreo3' Eimer & A~nd,
lot 492327.
= O.0703t.
0.0002
1956,p.210.
This work.
srC03'
Gen. Chem.,
C.P.,lot 10.
0.712
:t 000003
~.1195 0.0066
%0.0002 :to.OOOl
Srco3, Eimer & Amend,
lot 492327,
aver. of 8
.
analyses in nine monti~s.
Errors are the'st:andard deviations of the mean.
~ne agreement between the results of all of ~e
analyses
of 'the S!:'CO:;wit:h those previously
ctbe~ 1nvest19a~ors gives confidence
other isotope ratio measu~eme~~s.
necessarily
an indication
'stratesconsisi:ency.
accepted w1~
eight
reported
by
in the ~ality
of
Such agreement is not
of accu~acy bu~ merely demon~
A single measurement. cannot be
confidence
unless' it 1e part of a set of
lr-
similar
~asuJ:emen~s with which it: can be compared.
It
is well 1:0 :rememberthai: one out of the nine analyses of
the
srco]
bad to be rejec~ed even thou9h the run seemed
'to be of good qual! toy.
Conc:luslons.
The reproducib111~y
of measurements
is improvac1by as much as a factor
ratio
a fractionation
of the sr87/sr86
of j!our by making
correction based on the assumption
that the
sr86/srS8 ratio is ~. const.ant equal to 0.1194.
The reproducibility
of an oceanic basalt
..
:t O~OO~6
(O.O~)
by repeated
(R1292) and a srC03standard
analyses
is
and':t 0.0009 (0.12%), respect1vely.
on these results
of good quality
demonstrated
the reproduc1b111~y
is
aBs~d
to be
Based
of a single analysis
t:. 0.001
or 0.14%0
The instINman~ precision
sr87/sr86 ratios is a
quality of a run.
error
for the
useful crt'terion
re...eaeureri!.snt
for judging
of
the
Because it: is sma.ller than the repro-
duc1bl11~y it is unrealistic to claim a precision error of
-0.001 (0.14")
for the correc1:ed sr87/sr86
!:at;1c 'iFJhenthe
instrumont error alone has a value of 0.14%0
~e isotope ratios obtained for the
are in good agreement
Aldrichet
w1~
srco3 standard
resul~s reported by Nler (1938),
al~ (1953). and Herzog et ale
(195.3) and give
confidence in ~he accuracy of ,~he isotopic analyses of
s~ront1um in zacks reported in this thesis.
-lSSca
Tim ISO'lOP1C COMPOSITION OlF S'1'RONTlm~
!N OCEANIC AND CONTINENTAL BASALTS.
Introduction ...
Before the ratio of sr87/sr86 in igneous ~ocks can' be
used as acritex-1on
for a crustal or subcrus'tal o:ri9in~
the range of variation of this ratio in'rocks of known sub.crustal origin must be determined •. For this purpose a
survey was made of the isotopic
in a number of.oceanic
composi't1onof strontium
and continental
basalts
widely scattered geographic localities.
distribution
from many
The geographic
of the sample localities tests the lateral
an~/or vertical homogeneity
of.t~e subc.~stalsource
...
'
. regions of basalt magmawith respect to the abundance of
sr87•
All conclusions.and
calculations
in this chap~erare
based on corrected ,values of the sr87/sr86 ra~ioo The
nature of the correction
it are
and the reasons for'making
described 'in Chapter 5, page /77.
1ng the apparent homogeneity
~e
conclusions regard-
of ~he upper mantle are
not affected by the use of the corrected sr87/srB6
ratios.
as 1~4%.between success1ve
analyses of ~he same sample
(R1292,Chapter 5, Table 5.1~ P.I7S).
Th~s variation is
the result of isotope fractionation in the mass spec~rameteg.
Because
of Jot a reliable
determination
of the s&,86/8:("88'
ratio of a sample should be based on several
measurement.s spaced over an extended pariod
independent
of time .•
Ev1....
de~ce that the effects of isotope fractionation .1nthemasa
, spee~%om.eteraxe random is preasnted in Chapter 9 along
with a d1sc:~s~1on of the.- numerical. value of the
sr86/sr88
./
ratio.in
terrestr1almaterial
and tektites •
.The p~e~1Sionof the sr84/sr88 ratios
(r5").
Prequently
.n more'detailed
account is glv~n in.Chapter
9.
of. nib1dium and st.J:onUum in a
number of basai~s were dete~ned
method of isotope dilution
in order. to cOmpare
lev
only 12 to 18S.X'84 peaks were scanned •
The concentrations
representative
is very
(Chapte:r: 4)
0
by
the
This was done
the Rb/~r ra~los. of basalts
to ~e
calcula:ted .values of. ~he 'Rb/sr ratios in their. source
regions.
The RbISr J:a~ios of t~e magmatic
calculated
from the sr67/sr86
source mate&"1al W91:e
ratio' of Recent basalts by
aSBumi~g that the initial Sr81/sr86
"'z'O.C02 (Gas~. 19(0),and'thatthe
4.5biliion
years (~apter
ratio was 097004
age of the earth
1).
is
If,basalt or andesite
magmai!oms by part1.~l melting, of rocks in 'the upper
man~le, then the 'difference between the Rblsr ratios in
bas~li;s ancI'the' calculated values
of the source rcck,:is
~vlde~ce of magmatic'differentiation
Q~
of fractional
\r
melting' of the source rocks to produce
Another p~rpose of these analyses
tbe magma.
was to outline the
r~nge of variat1on'ofthe concentrations of rubidium
and strontium in oceanic basalts fer geochemical
in1:eres't.
Real variations
"'-
frOm
of the
sr87/Sx86 ratios in basal~s
~he same, or from d1fferentlocaliUes
are an indi-
,
cation tha~ magmawas derived
different Rb/~r rati9s.
calculated
from, several
Acamparison
of these ratios,
w11;h the assumptions,out:l1ned
found in different
souX"ceshaving
above, to those
types of ,ultrahas1c and basic
rocks
'may serve to give an,',indica'tion of the' nature of the
source material.
Analytical
Resultso
All experimental
data pertaining
to the basalts
are compiled in Tabla 601.
~'de6cription of the epeci-
mens as well as in.fomat!on c;.bouttheir .locali~ies
is
given in cnapter'lO.
Oceanic
Basal'ts.
The localities
an~lysJ.s
are .Hawaii,
Saiuoa, Ascension. Island,
the Mid-
and the. Azores •. In the 'following sections
AtlanticR1dge
..
from which specimens ware chosen for
\.r
the results will' be. discussed
fo;g eachof.theae
loca11't1es.
Hawaiian Islands.
The Hawaiian. Is~ands aX's a 9ro~~ of shield
'formed by flows-of
basal~s'and
primary
tholeeit.1c
either fozmed
crystallization'
of tholee1tic
basalt magma or represent a ..different'
. inatlng
fromot1)er
depth bf.th~s~
earthquake
. ~J
1960,p.
judging On the bas1sof
the base of the. crust. (Turner
219).
The isotopic compositions
Bb/Sr r~t1oB of'five basalts
were determined.
'l'he
t~ be be.tween 48 and 56
is: estima~
which 1sWellb~low
and'Verhagen,
m.a~1a series. or19- .
soui:.ce 8:'egions in the mantle.
source. regions,
focl,
lava •. Th.ec11vlne
derivatives
their alkali-rich
';as,<a r~sult of fractional
volcanoes.
of strontium
and the
from the Hawa1ianIslanda
The sr87/sr86
ratio
for one of these,
III
k
~
:a-,
en
~
~
N
.'0
11
tlt.
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•
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•
a basalt f~am Kilauea (R1292), wasm~asured
The average S'i:S1/sr86ratio
--+ ,
. ~
0-- ..,;.00026,
fo~ this
.'
five~imeBo
roclts ,is 007066)
,
'
<7"== - .00059 (Chapter 5, Table Sol,
po 178 )
0
The sr87/sr86 ratios of the other basal~$ from Hawaii
Island (R1282, R2001, and R1993) fall inside the band
O.1066.:t 0.0012(20-) •
They therefoK'edo not. differ
cantly from R1292 at the 95% confidence
signifi-
limit although the
possibility tha~ they belong to a,sllgbtly diffegent population 1s not ex~luded.
:t
O. 7069 :.t ~. 00025
.'
srB7/sr86
All four basalts average
fa: ) •
\)
The
sr87/sr86 ratio for a basalt from Maul Island
(R2002) is O.7~47%O.OOl
calculated:from duplicate analyses.
'this' basalt 'therefore seems ~o differ
the"other foUX'~ Ii: is customary 'to reject
..
that. 'two means are identical
..
them exceeds its own.error
(Evans, 1955"p.
D
= 0.0022
'deviations
746).
and.1-ts
the hypothesis
when the difference
ai: the 95% confidence
between
limit
In this case thed1fference
'eZ'J:ol:, ~.,
of the two means"
the evidence
from
considerably
calcUlated
is% .00106.
fram i:he standard
Since D ;;-
z.~,
1s suffic1sn1: to conclude that the two means
,are significantly
different.
of at least two source regions
have been derived.
t~
therefore have evidence
from wh1cbHawai1an
magmas
The calculated RbISr ratios for the ~wo source regions
are:
the Iaiand of Hawaii
P03:'
Maul Island. (RbISr)
11~ts
source
(Rb/Sr) eOUICce
= 0.022 Z 0.012.
0.034:t .011,
C
The errore
are
of uncertainty and do not necessarily reflect on
the p~ec1sion of these values.
~ ~ampar1son ~o the RbISr ratios of igneous ~ocks
(Chapter 2, Table 2.2)
'-r
material
shows 'thai: t:he magmatic: souzce
resembles .mos~ closely the basic: and ultrabasic
19neousrocks.
Moreo'ver"
it. is evident
t~at neither
chondx-1tes nor ~he achondri~es listed in Table 2.2 are
a suitable source material for the Hawaiianbasalts.
The
'Rb/$r ratio of the chondrites is ~oo high whereas that of
the achondrites is 1:00 low.
I't is unfortunate that: the
data"on the concentra~ions of rubidium and strontium in
~l 'trabasic igneous rocks are so fragment.ary.
survey of these rocks 1s desirable
values of ~e
systematic
if the calculated
RbISr ra~10 ~re to be used to identify the
.nature of the ma~at1c
eougce ma~e%ia16
The mean RbiSI.' ra~o
1~ O.024SZ:0.0005.
for the three
basalts
The rubidium and strontium
are remarkably unifoftl
:t 6.2 ppm,
A
respec~lvely.
from JCilauea
concen~ra~ions
and avez&ge 9. 56:!:0.31 ppm and 386
R1993, a basalt
from Mauna. Rea,
contains 46.7 ppm rubidium and 1249 ppm stron~ium but has
basa~t8
areB
=
and RbISr
Rb m lB.at'
9,,3 ppm,
8r
aD
601091: 209. ppm
O.031:t 00019 •.
RbIsX' ra,1:ioof the basal1:s from the Island of
The
Hawaii .1s identical
#
wi thin experimental
e1:ror, t~ the
RbISr ratio of their source region calculated
average~sr87/sr86
page
from'~he
with ~he a~sump~1onB ou~lined on.
•
The rocks of the Samoan islands belong to the typical
alkali-rich
olivine basalt association of ~he 'Pacific
petrographic province.
Two of the three rocks analyzed
.
are olivine basal~8, the third (RiggS) 1s an olivine
gabbro f!Ccm a volcanic
lr.ieckon. Ofu Island.
•
sr87/sr86 ratios fom
The corrac~ed
I
a homogeneous
set of values averageD
.
+
..
,
log 0.7077 - 0.00009.
The Samoan rocks differ significantly
on Maui .Island in their
sr87/s:r86 r'atioso
between atem and 'the rocks from the island
however, may net be significant.
from the basalt
The difference
of Hawaii,
The average concentrations
nb/Sr
and the
Rb
=
ratio
2S.Si:a.3
of rubidium
and stgont1um
Samoan'&"ocks aure
of 'the three
ppm, Sr :.419.8+105
ppm,
Rblsr
=
0.061-:-
The large standard deviations of 'tbemeans'
O.025c
a fairly wlde range of values which for rubidium
indicate
to 41.6 ppm and for strontium from 22205 to
is from-14.1
567.6 ppm •
.
~e
V"
calcula~edvalue of t~e
region' ~s O.03St ().Oll.
Rblsr ratio of ~e source
This value is less than the pre-'
sent Rb/Sr ra~10of the basal~s
and indicates
enrichment
of the basalt
(or depletion
of stl:ont1um)
magma in rubidium
relative to the souJ:ce ma'terial.
Mid-Atlantic Rid<;le. and t:he Azores.
AscensiOn Island.
\
87-
/sr
The Sr
86
ratios
.'
of 'the specimens
from Ascension
Island and the M1a-Atl~tlc) axe 0.7070 and 0.7062
0.00065
respect1 vely
«(f),
0
The value
for ~ba boulder
f:om ~e 141d-AtlantlcRidge is based on duplicate an~lyses
The sr87/SJ:86
is 0.7088.
zoat10 of the
oll,vine
basalt from 'the Azores
This is higher than observed in any of 'the
Concentrations
of rubidium
and strontium
waxe ob~a1ned
0
-195-
for the basalts from ~scensio~ Island and the ~dA'tlantic .~dge.o
Rb.
=
31.9 p~,
'the latt~r Rb
The resuli:s for the fozmer are
Sr
e
643.0 ppm, Rb/sr
= 9.75
= 000496 and for
ppm, Sr callB.3 ppm,
RbIs%'
:D
0.08240
The calculated Rb/Sr %atios .of the source material
,
of the b~salts a~e as follows •. Ascension
0.035, M1d-At:lant1c
Rblsr
= 0.044.
Island RbISr
Ridge. RbISr ::0.030, and 'the
=
Azores
'l"he.value. for the Azores is the highest
.0£ all oceanic basalts.
I..ummary.
All averages discussed ~n the previcu~ section are
summa~1zed
\
\
..
in
Table 6.2.
Table 602
Summary-of
Data on Oce.anic Basalts.
Noo of (87/86)
colt'r
Locality samples
Hawaii
4
0.7069 (0)'
+ 0000025
Rb
ppm
18.8
(Rb/Sr)
.. so~;X'ce
Sr
ppm
RbIsX'
601.9
0.031
0.034
:to.019
:to. Oil
.t 9 3 :t 209
0
..
1
MaW..
0.7041 (2)
0.022
:t 0.012
:!: 0.001
Samoa
v-
Ascension
Mid-'.
3
:!: 0.00009
" 1
1
r
j
.Averages
0.7062(2)
1
0.7088
11
0.7072
t 0.00033
\\
NOUI
0.7010(1)
25.5 419.8
0.061 0.038
:t 8.3 :tlOS
:t 0.025 :tOoOll
3'1.9
643.0
9.75 118.3
0.050
0.035
00082
0;.030
:t 0.00065
Atlantic,
Ridge
Azores
0.7077(3)
(1) A.ll errors
0.044
21.5
492.0
~ S.O:tl08.S
0.044
0.036
~ 0.014 ;to.Oil
are standard deviations
of t.he mean
or are calculated from them.
(2) The average RbIsX' ra1:ios were calculated from
the average concentrations of Rb and Sr.
(3) ~r
in b~acket8 indicates number of analyses.
-197ContinentalBasalts~
sr87/sr86 t:atlos were dete1ro1ined for 16 volcanic
rocks from eight continental
localities.
This part of
the invest:1gat1on 1s an important phase of the test of
the la1:eral homogeneity of the upper mantle.
toplccompQ!$it.1on of s~ron~1um entering
the mantle is of pagt1cular
the
The
180-
crusi: f:rom
significance for any inter-
pretation of the origin' of crust;al igneous rocks.
'Specimens'of volcanic
were chosen.
rocks from tbe following
loca11ties
Japan, Deccan 'lateau, Indiar Columbia
"
River area, Qregonf Di&ba~efrom New Jersey,Iceland,
Mt. Vesuvius, Italy.,., Yellowstone' park,'and
Squaw~reekf
Montana •
.The
experimental
\'
data are compiled
..
!nTable
6.3.
"
Japan.
Tb3:ee ~ocks f:ro:a
two
Japanese localit:les were
analyzed •. Two of .these are andes1 tesfrom.
the~1:rd
1s.a dac1t.e from Banda!
were e.X11pted
~e
0==
in historic
San.
All
Sakuraj lma,
three rocks
'time.
average corrected sr97/sr86 ratio1s 0.7081,
1:0.00013.
c:r-=:J: 0.00023.
sidered to l1e ou~side
Japan is. generally con-
the Pacific petrographic' province
- -198lot
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ex)
0
......
ON
00
00
00
0
••+1
•
•
N
C\
I'
&n
\0
0
\0
CD
.......
\0
~
\0
0
•
1ft'
~
Ln
0
C)
(I)
0\
\.0
0
0
CD
CD
1-t
0'\
.....
O~
....
...s
00
00
00
0)
• •
•
1-1 1-1
~
k
~CJ
0
...
;
0
\0
r-
~
l'
I'
CD
0
•
•
r-
~
N
....
s.n
\0
CD
0
en
0
,.....
00
0
l'
0
•
N
0
~
"•
•
"'0
0"-
CD
00
+.• ~I•
0)
'IlIIlI'
CD
....~
~
0
eX)
'a
.......,I
c
0
BIU
"..
.9
•
...
fP
~
C4
<:)
P-I
\0.
"...
~
~
::r
~
....
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0\
N
CD
::s
.a....
'nl
\D
"•
~
...,0
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u
~
en
~
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~j
f~
'"...
r:
cu
CD
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H
•
0
\0
0"
Q
..-4
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\0
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~
tn
'0\
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If)
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cu
.tJ
H
~
N
4t;St
~
U1
GJ
.,..
....(0IU
'a
CD
to
~
:::~
C
~
....
•.
1
1-1 +1
\0
~
~
Jp Q
....U
-.
fa
~
~
U
~'f)'
~
~.
C
~
an
In
00
OQ
r4
II
I'
~\O
. 0 ....
\0
~~
... ...
~
~
.&J
~
...
0
CD
•
"
co
(X)
N
\0
lid'
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:
u
........
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ca >
........
o &'0.
........
s:
& Z.
"'....
.......
~m
GJ c. 0
~82
and to fall
inside 'the -andesir;;eline.
It is therefore
of interest 1:0 ~cmpalte the averagesr87/sr86 ratio of
the Japanese
:rocks totbose
'test for the difference
for
Hawaii and Samoa.
of two-means reveals
Japanese rocks differ significantly
and Samoa, witb1ng
experimental
The
th-at 1;he
from those of Hawaii
error.
The calcula~ed RbISr rai:10 of the source z-Eg1onis
0.040 t.O.Oll wb1chis not too different: from the value
Hof _thls_~at10
in olivine ~~salt8.
The concent~a1:1ons of rubidium
-'. andes11:es
and
Deccan Plateau.
and strontium
in
'the
'the dac1 te were not detem1ned.
Ind:1a.-
-'the t:holeelt1c basalts of the DeccanPlateau in
)
western_ India
toClay occupy an area ..of 200,000
.
miles
\
and naacb a max1mum~1c1tness of
Bombay.
This. immense -quanti t.y -of ~asalt
in Cretaceous
square
.. EOcene 'time.
6000 feet
near
was extruded
'the rocks resemble closely
in chemical. compoSition and volume similar o~currences
. in 1:be-Columbia - .snake River area of WaShington,
ana Idaho, ~he Ke~enawanlavas
S~rcmber9 ..1avaB of _South Africa,
of Lake Superior,
the Triassic
Oregon
the
diabases
-
-202-
of New Jersey, and ~he Paranao basalts of South .»meriea (Turner and Verh~gen,
1960, p •.205).
The 1s0'top1c composi1:ion of strontium of three
basalt spec~mens
m1ned.
from the Deccan Pla~eau were deter-
The .average correC1:edSr87
O.7089.~= ~ O.00019,~~
has
.of .solidification.
The.
(R1864) is 0.069.
ratio of
°If the age
tha
increased by 0.0003 since the time
The initial
ratio
would
therefore
average sr87/sr86 ratio for 'theDeccan
basalts is very slightly
ese volcanics.
i!!i
is taken .i:o be 100 1Qi111on years,
sr87/sr86 ra~10
be 0.7086.
ratio
* 0.00032. The Rb/Sr
one of the. three basal~s
of the basalts
/sr86
higher than that of 'the Japan....
The .calculated Rb/Sr ~at10 of the source
region is 0.043%0.011.
Columbia River Plateau.
Oreqon..
Three specimens of basalt were selected
Unfortunately
the resul'tsobta1ned
for analysis.
on two of these
(R1435,
R1443) are of inferior: quality because
of instrumental
difficulties
spec1ment (R1428)
(poor vacuum).
was.analyzed in triplicate
8:87/sr86
= O.7067:t
The ~ixd
and the average of 'these,
0.0001, . is considered to be 'the best.
estimate
of the t"roe value.
Specimens.
R1435 and R1443
average 0.7113.
concentrations of rubidium and strontium of
~e
R1435 aze Rb
a
54.8 ppm, Sr
=
=
310.6 ppm, and RbISr
0.176.
Since the .age ,of the basalts is Miocene
~llion
years) an age correction of 0.0002 is applied ~o
the average
srS7/8:r:86 ratio.
'lbe best: estimate
.a~10 1s therafore
s~7/sr86
initial
(25
The'calcula~ed RbISr ratio'of ~e
of 'the
0.7065:to.'OOOl.
sour~e region is
, '+ 0.011.
'
0.032,'Triassic
Diabmses',of Mew Jersev and Connect:1cut •
. TwO specimens
of diabase from the Palisade sill
(~4209, tt4210) avorage s:87/sz86
14 1:hird speciman of diabase
cut.
was.
ratio
= 0.7094
bebieen
Since
analyzed
The average
Connecti-
srB7/s:r86
The test for the difference
two means shows that
D~ 2 ~,
from Nt.. Carmel,
in' duplicate.
0.00065.
= O.7075z 0.00045.
the a1fferenc:e
D•
is
-
,0.0019,00.=:1:
'
0.00079.
significant, However,
because the age of these diabases is apprOximately200
mill:l.on years,
~ed1fference
in the ,amoun~s of r~logen1c
solidification
may
be'due
to differences
8%87 accumulated
of the magma. Since analyses
since
for rub1dlWl1
and stxont1um axe not available,
'ra'tio for all
three
the aVGxage sr87/sr86
rocks is calculated
corZ'sction is applied
and an age
to the average on 'the assump't1on
that RbISr :. 0.1 and the age is 200 million years.
best est~ate
= O.7072,cr=
is therefore sr87/sr86 =0.7081
The
- 0.0009
~ O.0007~cr= ~ 0.0012 •. The calculated
Rb/Sr
zoatio of the source region 11' 0.036%0.011.
Miscellaneous
Localities.
Single 1so~pe
rat1~ analyses were perfcxmed on
basalts from four continental
ratios of these area
localities.
The sr87/Sr86
IcelCUlda 0.7101, Mt. Vesuvius,
I~alYI 0.7082, Yellowstone
Park& 0.7084, Squaw Creek,
Montana& 0.7096.
The olivine baBal~ f~om Iceland is pOBt-Plels~ocene
in age and ha~the
highest abundance of Sr87 of any
~asal't encountered 1n i:he survey.
sOurce region has a calculated
Its
sUb-crustal
Jtb/Sr ratio
~ 0.051 :t
0.012.
The .ar87/sJ:86
ratios of tite
o~eZ'
X"ocke are well
wititin the range of what may be considered afJeraqe ' .
.sub-czustal
of Tertiary
s'trontiUJJl. The basal't from SquawCreek is
age.
Assuming an age of 50 million, -years
and a Rb/sx ~at10
'=
by 0.,0002 to 0'.7094.
0.1, its sr87/sr86 ratio is reduced
The RbISr
source :regions, are as follows:
ratios calculated for the
Mt. Vesuvius 0.041,
Yellowstone Park 0.042, squaw Creek, Montana, 0.047.'
Summary.
The results'discussed
summarizad1n
1n~epxey1ous'sect1on
age
Table 6.4.
'Table 6.4 Summary of Data for Continental Basalts a~
the Tima of Their Extrusion.
Locality
lfo. of
Itb
Sr
Spleso(87/86~orr
ppm
ppm
Japan
3
(Rb/Sr1
~b/sr
.7081
+ 0.00013
~ccan
3
'Plat •• India
.70a6~
:t
16.1
234.9
00069
. 0.00019
Columhial
0.70650(3)54.8 '310.60.176.
Riv.,
0.0001
Oregon
Tr1asslcD1a-
base,
1
0.040
0.011
0.043
:to.Oll
0.032
r 0.011
0.036
30.7072*
':!: 0'.011
.New Je1esey
Xcelilnd .
~ource
0.051
O~7101
:t 0.012
Nt.Vesuvius
1
0.041
0.7082
~ 0.012
I~aly
Yellows~one
0.042
1 0.7084
:t'O.012
'Park
s~aw'Cxeek
1 0.7094*
0.047
:t 0.012
Montana
Average
14 0.7083
z.,O.0004
*
35.5
272.8
:t19 ~)4 ;t 38
small age correct1~n applied.
0.13
t.. 0.07
0.041
.:to.Oll
Conclusions.
The, average
volcan1cr~ks
continental
0.0012.
s~87/sr86 ra:tio for
of BUb-c~stal
'locall ties
is
=
25 basalts
and other
origin f~om oceanic and
O.7078J 0= = :f: 0.0002, f:r
= :r:
The values range from a. low of 0.7047 for a basalt.
from Maul Island to 0.7101 for an olivine basalt from
Iceland.
The average
localities
Sr87/sr86
for eleven basalts
.1s 0.7072 :tOo0003.
from continental
localities
from oceanic
Pourteen volcanic rocks
averags O~7083%0.0004
0
The difference between
oceanic and continental ba~alt3
.
'
is probably not: signific:an1:. Although tbere is a tencisney for continental basalts to ,have slightly higher.
srB7/sr~6 ratios than oceanic basalts,
exceptions are
common.
The magma~1csource regions in the upper .mantle are
therefore homogeneouswithin narrow limits .. The limits. of
homogeneity
0.7078 +
e~ressed
in teJ.'tltS
of t:he Sr87/sr:8~ raUo
are
0.002.
- 0 ..003
The
Rblsx gat10 for the magmatic source regions, cal-
culated from the average sr87/sr86 ratio, is 0.039 ranglng from 0.022 to 0.051.
The upper mantle is therefore
-201homogeneouswith respect
i4>/sr
limits
=
to its
RbIsX'
ratio
within 'the
00039+0•012 •
.
- 00017
source re9~ons have a calculated
The Bub~eanlc
RbISr ratio of 00036 whereas the sub-continental
sources
average 0.041.
Small but real differences
be~weenbasalts
from different
in the sr87/sr86 ra~!o
localities
seem to exist.
Such differences are evidence that magma was derived from
more than one source
,and
that small variations in tlle
Rblsr ratio of ~e upper man~le ex1B~o
Small differences.in
sr8'/sr86 ratio are diffi-
the
cul~ ~o de~erm!ne reliably because. of isotopic fractiona.
'
t10n in 'the mass 'spect:rome~er.
partly
by applying
'this
can be overcome
a fractionation correction based on
a constant value for 'the Si:86/sr88 ratio and by making
several independent analyses spaced over a period of tim9.
The conc~ntrat1ons of rUbidium and stron~1um ~n the
oceanic
basal'ts
.respectively.
average
21.50~ 5.0 ppm and 492% 108.5 ppm,
Rubidiumconcentrations
range from 9.13 to
46.7 ppa'lwhereas strontium concentrations
118.3 and 1249 ppm.
vary between
'lhe ~b/Sr ratio, calculatedftom t:he
average concentrations, is' O.044:t 0.014.
Concentra~1ons
of rubidium and strontium for thole-
eitlc basalts were detaxmined
average values
are Rb
=-
foz only two rockso
+
35.5-1904,
The
'm.
_
+
pP.'
Sr - 27208- 38e The
DDn7
IT
corresponding average RbISr X'atio is 0.13 zOo 07 •
Thole-
e1~ic basalts ~erefore seem ~o have a higher Kb/sr xa~10
'than oceanic basalts •.
of the RbISr ra~1os of .the basal~e
A comparison
with thoBe calculated
for their source regions may give
some indication of ~be processes
of magma foxmat1on.
Generally ~he RbISr ra1:1os of t:he rocks are higher 'than
those of ~e1r
source material.
Rb is enriched
(or SE' 1~ depleted) in t:he liquid fraction.
~e
only exception
This is evidence that
to this occurs in ~e
basalts
from the
island of Hawaii where the Rb/Sr ratio of ~he basalt: 1s
1dent:1calto 'that of tbe1r source.
This may be 1n'ter-
preted as evidence of essentially complete mel~ng
the source rock.
may bt! identical
of
If this 1s .true, the lavas of Kilauea
'to 'their sub-crustal source material
..
with ~spect
'to the concentrations
of major elements .as
well.
A comparison
of the Rb/Sr ratios of ~e
source regions w1th tho~e. of certa1~e
magmatic
of igneous
rocks may give same indication
mantle.
According to Chapta~ 2, Table 2.2 olivine basalts
and i:be eclogite.have
0.045.
of ~he nature of the upper
identical
Rb/srrat:ios
at abou~
Very similar values are indicated for the source
regions in ~e
following loca11~iesl
Deccan Plateau
(0.043), Nt. Vesuvius
Park (0.042), S~aw
Japan (0.040),
(Oo041), Yellowstone
Creek (0.047) and the Azores
This similarit.y does noi: necessarily
above mentioned volcanic
melt1ngof
(0.044).
provetha~
the
rocks .\tIGre formed by partial
a basal~1c or eclogltic mantle.
Other ultra-
basic rock 'types such as per.1doti'tes, pyroxen11:es,etc.
may have suitable Rb/Sr ratios
possible interpretations,
concentrations
as well.
Because of such
a comprehensivesurvey of the
of rUbidiUM and strontium
1n ultrabaslc
igneous racks is highly desirable.
Neither chondritic
nor achondr1~lc
meteorites
listed in Table 2.2 are a suitable source material ~or
Recent .basalts.
The Rb/sr J:a~10 o~ chondrit.ic meteor-
ites 1s'too high whereas 'that of the achondri'tic'meteoJ:1~es 1st.oo low.
-210-
sr87/Sr86
Tim
RATIO, IN PRSCAtmRZAt~
BASIC INTRUSIVES.
In~roduct1on.
The isot.opic
material
of
compos:!.
i:10il of
the soux:ce.
basalt: magmacan be determined by analyzing.
Recen't basali:s~ 'The value
billion
s~ront1um of
of 'the 87:87/8r86 ra1:io 405
yeu:s ago is known from measurements of t119
achondrite pasamonte (Chapter 1). With 1:1118 1nfoxmat1on
a development line for ~e
crustal
siC~7/sr86ratio in the! subc:a
source regions throughout geologic. 't1me can be
drawn (Figure 704).
An attemp~ has been made 1:0 determine
of
this devel~pment 'line 1ndapend~ntof
'the slope
any mete~rl~e
,data by obtaining ini tlal .sr87/sr86 ratios' for basic
.igneous intrusives
of subc:.CruS'talorigin
,
us
known. ~e
'
samples chosen foX' 'this study are
frcm tile Bushveld Complex 1n South Africa,
Duluth
whose ages
Gabbro in Minnesoi:a.
and 'the
Introduction.
,
T
-
-.
The basic rocks of the Busbveld Complex are the
prOducts of frac~ional crystallization
~1on of a large volume of basaltic
and differen~1a-
magma.
They are
overlain and in~ruded by the so-called -RedGranite"
0%
Bushveld, Granite.
'rhe relationship
'to \;he basic rocks is not clear.
(1960, p.298)su998st
of the gran! te
'l'urne'r and VeJ:'hoog~n
that all 19DeOus rocks of'the
Complex belong ~o ~he same cycle of igneous activity.
Concentrations of rUbidium and strontium as well
as
sr87/sr86 ratios were deteJ;mined for three basic
and ul'trabas1c igneous xocks in an attempt
-the io1 tial
ar87/sr86 ratio, at; the
,'!'he Age of the
Schreiner
Bushveld
and
.three
time of emplaeement,.
Complex.
(1958) :r:epo:r:ted
Bra average age of 192~
m11110n yesxs by 'the Rb-S:r: method
ites
1:0 measuxe
feldspars
separated
for
fCNX' whole
from
them.
gran-
W.S
data have been recalculated and are presented in
F1gure 7.1 in diagrammatic
J:oclcs . (921,
fOnl.
Three of the whole
810. arid B6) form an "aX:l"ay" end conve:r:ge
. -212-
1
I
,,
1
~,
I
I
I
{):I
87 86
SrlSr
I. 500
(/)1
0'
iii'1
Ii.
1
iV'
FIGURE 7.1
Sr DEVELOPMENT
LINES
FOR RED GRANITE,
BUSHVELD COMPLEX,
SOUTH AFRICA
1.400
llJ,'
I
I
,,
,
I
,I
1.300
I
I
,
SCHREINER, 1958, R 114
I
I
I
,
1.200
I
,,
I
I
,I
I
,,
1.100
I
,I
I
,I
1.000
I
I
I
I
I
I
I
I
,
I
I
I
I
I
I
I
0.800
I
1
I
I
.., ...-
;I'
1/
... "~ ,..."
);1'
0.700
3
,
2
TIME
IN
BI LLIONS
OF
YEARS
923 probably
does not differ. sign1fican1:1y
three whola rocks.
The feldspaJ:s (B21. 810 and B6) seem 'to
d1fferen~ array converging
fo~aslightly
from i:he otheX'
.'t Ii 2225 andsr87/sr86
.:;.740.
at about
The reason for 'this
ence ~s not. ~lear.and .it may not be s19n1fican~.
ing to Schreine,r's data .the initial
Busbveld Gr~n1t.e 1s""'" O.740. ~ch
Accord-
sr87/sr86 ratio of the
definitely
sub-crustal origin for this rocle. ~reover,
the underly1n9
differ-
excludes a
the .9raniteand
b&s1c roclcs canno~ ..be co-magmatic •.
N1colaysen e~ ale (1958) ~eported a Rb-Sr age ~f 1915
%50.
~111on
. mica-pyroxene
years fo~ biotite fxam a coarse-grained
gabbro at 'the Rustenburg
same authors'also
~f
The
obt~;I,i1edU-Pb arid '111-Pbages on crystals
monazite and zlrconfrom
cluded that:
Platinum Mine.
an age
the Bushve1d granite.
of 19Sof 150 miliion
They con-
years for both
the granite and the basic xocks was con&is~ent with 'their
results.
B~r1mental
RSsul~s.
The anal~lcal
data are shown in !'able 7.1. and are
present.ed graphically
raUo determinations
*recalculated to
A
in Figure, 7.2 •. Only single ls0~ope
were. made foX' each Z'oc'kand an error
:a. i.~41,.Xl0-11 yrs.-1
oftO.OOl is assigned
to
The erroZ's
the ~ld1um
SbOit1n
.are considered
for
the'co~rected sr87/sr86 rat1oso
to be realistic
ana strontium
eB~~ates
of the reprodu-
cj"b111ty at the part1culaJ: concentration
T~le
4.6).
Descriptions
analyses
levels (Chap~er 4,
of ~he rock specimens and
infozmation about ~he sample localities are given in
Chap~er 10.
Discussion •
. ~)
sr87/sx86 ratios ls'consls~ent
The pattern o~ the
with the llb/Sr ratios
ment lines
1n the three rocks.
conyeE'ge 'toward a point. at about 4.5 billion
y~ars an~.a sr87/sr86'ra~1o of 0.707.
large er~or.envelopes.make
In. fact in~ersecticns.'are
~eBe values meaningless.
All intersection
at about
years 1s tilerefore. not excluded by th~ da1:a.
Intersections of ~e
81:J:ont::1umin
yeaX's
HOwever, the
obsezved from zero up to
about 14.3. b1111Qnyears.
2 billion
'l'he develop-
the1:hree
give' (sr87/Sx8~)o
development: lines. for 1:he
rocks .w1ti1 t:
as
O.110~ 0.001,
and 0.707't, 0.001, respectively.
xat10 of the anorthosite
= 1915% 50 million
0~708t:.OoOOl
Since the arB7/sr86
1s a1mos~ constant
in time,
.1'ts 1n1Ual raUo of O.707Z0.001 is cons1dexed to,be
-215-
~
en
i
...... ~
I:
{Q
121
....m•
-.8
"')
0m
• fa
•
K
,
.!l
•
i
...•
~
ig
.....,
j
.
"'S
~~
~ +1
.....
CV)
,
'N~
. ~ ...
o .,..,
::~
•
J
J
~~
oN
"
...
U')
\0
~
Q
m
~
\D
CD
w
~
~
~
r\0
.......
•
...
0\
00
...
0
~
I'
CD
"r-•
CD
....
it
cnRS
~
N
..t
•
.-..0
•
1'-.
...0'\'"
00
1'0
• •
1-1
r--
(f)
....
f"-
Q
0
....
•
r-
0
\0
0
\D
0
~
~
~
~
..t
~
S....
....
I!
•
0
0
...•
....
1-1 .
Q
./
N
I" .... . N ...
It')
oN
0
0
0
...
~
~
•
CO
.....
'"'!l&
O\Ul
...
•
r-o
0
•
&
~.8
0..@IO
.~
0'\
...
it
...
...r
•
I
B
1:
S
cae
~
1ft
...
:
en
+1
\0
0
0\
• •
t")
N
III
\0
CD
00
,)
en
0
0
en
..... (\1
~~
0
<:)
NO
'~Q
......+1
CD
~
......
. ..
• •
.(W1
lot
\0 ....
a. ....
.....
0
NO
00
00 . 00
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-217-
the best estimate of this ~antity
for the basic rocks of
the Bushveld Complex.
Figure 7.2 111us~rat9s
the difficulty
o~obtaining
p~~c1se age values,and initial srS7/sr86 ra~ios for
rocks having such low RblsJ: ratios.
'The precision
of
the measuremfJntscan be improved a~
the reBut tsmade
moxa meaningful by ,making a11'aetem1nai:ions 1n'triplicate.
Conclusions.
'.rbe age of 1:he basic: igneOUs
complex 18 1915'%(~o million
rocks of 'the Bushveld
years
1958).' An attempt tode~r:m1ne'
(N1c:olaysen eot al.,
the1x srB7/sr86 'ratio
,a~ 'that: t1me me't with 1nd1ffezen't 'success becau~e o~
the low precision of the measurements.
for 'the 'in1 Ual
sra1/sr86
The best value
X'atio is o. 707 t. 0.001.
\ '!'he Dului:h Gabbro.
Inb:oductlon.
\
~e
D\llu~
Gabbro COmplexis an immenses1l1-Uke
,
,
mass extendlnglS0
sota.
I~'
1I11es noZ"~'
east "from
Duluth,
was foxraec!by repea~ec1 In'tzuslon
.Minne-
and crystalli-
'zat.1on of feld~path1c gabbro,. layered gabbro, grano-
-218-
d~or~te ana 9ranop~yxe.
Lack of chilled margins indi~
~~t~s that the sepa~ate i~tru~ions took place in ~ela-
t1vely rapid succession.
be explained
The variou~ rock ~~s
in 'terms of dlffereni:iation
can
of a common
p~rent magma of basal~1c c::~position (Taylor, 1956, p.42)o
1\~
~xcellent summary of 'the geology of the Duluth Gabbro
Complex was given by Goldich et ale (1961).
~e
Gold1ch
age of
theDulu~,
'Gabbro as reported
~
by
"
et ala (1961) 1s abou't 1100 million
years.'
'l1lis
is an average value of several 1ndeP.E!ndentdeteminationa
by the K~Ar mathod on several
samples from
different localities.
A single specimen of gab~ro was analyzed for its
~ldlum
ratio.
and str:on~1um.content
~nd 11:8 sx87/sr~6
The stratigraphic position of the specimen 1n
the Duluth Complex is \noi: 'known.
~rlmenta1
Results~
. The analyt1ca~da~a areehown
in ~able 7~2 and
Pigure 7.3 •. 8rr~rs' assigned ~o the corrected sr87/sr86
ratio and.the concentrations of rubidium and strontium
axe considered to.be realistic es~1mates of the reprodUC1b111ty.
-219-
I
I
s~js~6
I
0.713
I
I
0.712
,
1--- -
... ..... ---. _ ..... --
-- I
------------------0.711
0.710
OU\..lJTH
GABBRO
-.---- -~----------- ------------~
I
.---r-~8-;~~~:~-0.70920.001
0.709
0.708
ok
0.707
I
I
0.706
0.705
0.704
I
I11100,
0.703
M.Y,
0.702
500
1000
AGE
IN
FIGURE
MILLIONS
7.3
DULUTH
OF
YEARS
GABBRO
-220Table 7.2 Duluth Gabbro
Sample
No. of
Nu~t9r Date
87/86
(8!./86~orr86/88
R1231 1/~2/61 .7125
".7101
84/88
Qualit:y
scans
.1186 .0067 84
'j: 0.001
,J{b
= 6.8.0
ppm :t~,
SX'
= 34S~7 ppm ~'2%,
Rblsr
O.0197t:O.0007
s
Discussion.
The X-Ar .age' of 1100 mil11on' ye~s
minimumage"for ,the rock.
probably a
is
The 1nlUalsr87/sz86 'ra~lc
)
fox the Duluth Gabbro is therefore
.
+
loss than 0.7092 -
O~OOl.
Summary and Conclusions.
Th~ analytlcal.J:88ults for three basic.and ultrabasic: igneous rocks from
~e BuebveldComplex are not
.
"
.with an age of 1915:'
50 million
..
1n~n81stent
years
)
(Nlcolaysenet al. 1958)•. 'the best estimate of the
sr:87 /s~6
rat:1.oat
,
A single
"
t:118t: time '1s O. 707'" o. 003
,
gabbro specimen
- 0.001.
from tbe Dulu'th Gabbro
l
w~
found,~o bave bad,a 8r87/sr86 ratio of 0.7092 %
O.OO~ about 1100 million yeaz:s ag~.
Figure 1.418
matle fo~.
a sUlIIDIlry
of ,the results
in ttiagram-
~ck'o' precision of. single detezminat10ns
<10221,
does not allow much confidence
in the numarical
values
-\
do not disagree
0%
invalidate
'the hypothesis tha~ 'the
sr87/sr86 ratio of the upper If,lantlehas increased
~rOU9hout
geologic time. approx1tn~tely as indicat~d.
in Figure 7.4.
-The precision
GJ:%OZ-S
can be decreased
and 'the
\
results made mote meaningful
cate analyses.
J'
Table 5.1.
by duplicate
or tr1pli-
Compareanalyses of Rl292, Chapt.er S,
-222-
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Part. 1
THE .naB OF .nN ECLOGITE BY THE Rb-Sr r-mTHOD.
In1:roduci:ion~
In zoec(!ntyears the hypothesis has 'been debated in
the literature whether the MOhorovicic
discontinuity
a phase change from eclog1te 'to basalt
OJ:
is
whether it is
a chemical and physical boundary between a peridotite
mantle and the sialic crust.
The debate was opened by Lovering
g9s'ted t;hat achondrlt1c
meteorites
mantle of a dif~erentiated
'therefore most. closely
(1958) who eug-
are derived from the
parent meteorite
body and
resemble the mantle of the earth.
Pointing to similarities
in the chemical compositions
eucrit1c achondrites, basalts,
of
nor1tes and ~clogites he
proposed that the upper mantle is composedof' 'eclogite
and that the MOhorovicic
discontinuity
dary bet.ween eclogit.e 'and basalt.
of t.he Moho under the continents
from estimates of the p~sBure
at the Moho he estimated
is a phase boun-
Prom the known depth
and ocean basins
and
and temperature conditions
the.P - T curve for this ~rans-
formation.
OU~
In support
of ~e
hypothesis
Lovering po!nt~d
tbat the heat flow measu&'Eid at 'the surface
ei,lr'th
CQuld.be
accounted
of t:he
for if 'the upper 200 - 300
kilometers of the man~le are ~omposed of eclogite and
'the concentrations
of U, Th and K decrease ~1~ depth.
The occurrence of diamonds in eclogite
xenoliths
found in
k:Lmberl1
te pipes 1ndlca1:es that the source of these ecl~
gites is at a deptb of at least 130 - 190 lan.
Similar
sugge~t1ons have been made before
(1914) and Holmes (1927).
Goldschmidt .(1922)
by Permor
proposed the
existence of an eclo91~e layer between levels of 120 to
1000 'km.
Birch (1952) on 'the basis
eclogite
of s~udies of .1ncomca
to' a depth of 300 or 400 laD.
Kennedy (1959) discussed the application of ~is
hypothesis
problems
to .tbe solution of fou~ impor~ant
geologlcal
I
of continental plateaus.
1.
~11ft
2.
Subsidence of geosynclinal
sediments 1n'to a denser
substratum and their subsequent uplift
20 fom
mountains.
3.
~e unifo~ty
of heat flow a~ the surface of
continents and ocean basins •.
4.
The diacxepancy between the rats of erosion and the
11fe~ttme of eont1nen~B.'
Kennedy concluded ~hat these ques~ions could be
explained qualitatively
by assuming
phase boundary between eclogite
'that the Moho is a
and basalt and that its
position is controlle~ by temperature
and pressure conditions.
MacDonald and Ness,(1960) ~xami~ed the hypothesis in
'the light
o$: ex1st1n~ experimantal
that altbough the hypothesis
evidence.
They showed
could be' used to explain many
problems connected with orogenies and cont1nen~al
the expe~mental 'evidence :La insufflcient
O!:
uplift,
to either prove
disprove it..,
Harris and R0W811,(1960)
no theoretical
ofmeteox1tes
justification
pointed out that there 1s
fer using the composi~1on
in quanti~ative calculations of the composi-
tion of tile earth.
would be 60':' basaltic
An achondr1t1c mantle in particular
which cannot be rQconc11ed with
heat: flow measurements.
Moreover, partial
melting of a
basal~1c mantle would g1ve rise to rhyolitic or phono11tlc
magmaand one should expect these
reeks
dan't on tile cont:inents and in the oceans
are.
to be more abun-
'than ~ey
actually
They favoured a mantle of per1doUt1c composition
citing as evidence
~e
occurxence of ultrabasic nodules
in baa~lt and the e:ustence of.ultrabas1c
nonCl:>differentiated or1gine
If
rocks of pr1~a~y
the uppermntle
is
composed
of eclogite, fragments of eclogite should be found in
oceanic basalts.
In faci: eC1O<Jite
xenoliths occur only
in .k£mber11te pipes \~1ch are restricted
to the 'continents.
According ~o Powa~s (1955, p. 93) and Kuno (1959) in
Turner and Verhoogan (1960, p. 219) eclogibl
xeno11ths are
found in lavas of the Honolulu series of Oahu and the
Koloa serlsofKaul,
of Abundances of St:ront;lum Isot:01)eS in Basal f-:!,
~Dl:lcat1on
~
~~
Hawaii.
Eclogite problem~
Measurements of 'the srB7/s%,86 ratios
and continental
of bcen~
oceanic
b~salt:8 allow an estimate to be m~de of the
Rblsr ratios .of
their .sou:r:celDate~ial•. '1'bus 'the possib11tt:y
..
is here given to compare the 1O)/8r rat:1os of eclogites
those of ~e
whei:her
OJ:
source material
not eclog1b!s
from wbich to derive
isotopic compositions
of basalts
axe a suit.able
basalt
magma.
ana
to .de'term1ne
soUZ'cema1:er1al
By analyzing .1:he
of strontium and the concentrations
of I\b and Sr in several phases of the eclogite
be possible to detexm1ne.the time of its
An age of 4.5 billions
to
it. may alao
cJ:ystal11zationo
yens would be a strong argumen~ in
-227-
favour of the emstenca of emeclogi t.e layer 1n 'the mantle.
Wi'th 'tllese c:ons1deraUone in mind a series
of maaeurements
was undertaken on a~ eclogite from a kimberlite p1~
Robe~t Victor Mine in south
at ~s
Africa.
Geological Summary.
The diamond-bearing
upper Dwyka shales
kimberlite
pipes intrude the
which are of Mesozoic
The pipes
~'e.
contain abundant xenoliths of all reeks in the stratigraphic
section.
The emplacslDBnt
to have been preceded
rock fragments fell
lite
magmacarrying
up•
.A detailed
of ~e kimberlite
by a gas explosion
back into 'the cavity
diamonds and xenoliths
magma1s believed
following
wh:Lch
in which kimberof ecl~1~e
walled
descrlp~lon of the geology and t:he occurrence
of diamonds in the kimberlite
was given by Williams (1932).
ExPerimental Data.
The expezimental resul t8 are 91yen in Table 8.1.
a graphical representation .andinterpretation
r8$ul1:s see Pigure a..l.
detail
in Chapter 10.
of these
'I'he samples aredescrlbed
in
For
-228-
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Discussion of the Resul~so
The ..
average corrected sr87/s:r86 of the eclogite was
found to be O.708S.:t0.00075.
value of 0.711%0.003
it-yo
Rb/sr
The
1"especti~ely.
first
As
a
for an ~clog1te from the same .local~
~aUo of
th$ concentrations
GaSi:,(1960) reported
this
rock is O.0463.:t.0.0006 while
of Rb and Sr are 6.9 and 149.0 ppm,
far as 'the author is aware 'this is the
and only detexm1naUon of the rubidium and strontium'
concentrations
in eclogite
from the kimberlite
The sr87/sr~6 ratios of continental.end
range from 0.705 to 0.710 (Chapter 6).
pipes.
oceanic basalts
If 'this variation
is ~eal, the calculated Rb/sr ratios of the sub-crus~al
magmatic
source material range from 0.022 to 0.051.
These
calculated values are based on the assumpt10n that the
.iniUal
s~7/sx~6
ratio
is O.7004:tO.002 and that
of the earth is 4.5 billion
years
(Chapter 1).
gave values of O.014.~o 0.060 fox ~~s
ratio
of the ecl~1te
.
The
Rbis:
This is compatible with the
that at least same basalts could have been
derived from an. eclo91~
evidence,
Gas't (1960)
is w1th1~ 'the range of values 1nd1-
cated for the upper mant.le.
hypothesis
ratio.
the age
layeX' in ~e
however, does .no~ prove that
actually composed of eclogitesinoe
upper mani:le.
This
the upper mant.le is
peridotites
or o~er
ul~rabas1c rocks may have similar Rb/sr ratios.
Assuming that measurements could ~
made suffic1en~ly
accurately and tha~ ~he distribution of radiogenie srB7 was
not changed during the intruston
.of the,kimberlit:e magma,
the-time of crYsf::al1iz8t1on of the eclogite
inea.from the point of intersection
ment lines
can be determ-
of the B~rontium develop-
of the whole ~oc1c, th~ pyroxene, and ~ba garnet
(Figure 8.1).
Unfortunately, the results are .ra1:her 1ndiffel!-
en1:•. The following observations
can be madec
1.
The general pattern of the abundance of Sr87 1s compa~1ble with the present RbISr ratlos:.of ~he different
pbases.
2.
The error envelopes for the development lines of
strontium in the. pyroxene and the whole rock ov~rlap.
The two are therefore indistinguishable w1~1n experi-
mental erzoor.
3.
Al'thougb the pyroxene is enriched in Rb (13 ppm) 'the
garnet has the hi9hes~ Rb/S~ ratio and consequently
has the highest
4.
~e
5.
If the initial
sz:S7/sr86
ratio.
.strontium development 11ne of ~he 9arne~ intersects those of the pyroxene and 'thewhole rock at
12.6 and 11.OS'b.y~, respec~ively.
sr:87/sr:86raUo is as'sumed t:o be
O~700r O~002f the following intersections are obta1necf:
Pyz-oxene
Gamet:
and whole rock.
4.6:t 1.8 b.y.
2.0
5•g+
-1.5 b.y.
-232-
Conclusions.
The Ilb!Sr ra't10 of the eclogite
is 000463'1: 0.0006
which is w1tb1~ the range of values of this rat:10 for
the souree 9f basaltic magmas.
The ~oseib111ty ~bat
some baaalts are derived from an eclogite
layer in ~e
upper mantl~ is therefore not excluded.
ar87 developed in
The pattern of the radiogenic
the whole.rock a~d the garnet and pyroxene phases does
not lead to an unambiguous
of cry8tal11za~1on.
dete~nation
The evidence does seem to indicate
a very old age for ~he eclogite.
.determining
low concen~rat1ons
causes relatively
theposs1b111ty
The difficulty of
of rubidium and strontium
large expeZ'1mentalerrors.
'the intrusion
destroying
MorC!lover
~xists that a re-d1stribution of radiogenio
srB7 between ti1e pbases of the ~clogite
during
of the time
took place
of 'the kimbezo11te magma, thus
the st:Z'on'tiumdevelopment
pattern.
-233-
Part 2.
THE AGE OF ,.THE ELY GREENSTONE
AND THE SOUDAN
FORMATION IN MINNESOTA.
Introduction.
'the Bly greenstone
and .the Soudan
iron formation
.belong to ~he oldest volcanic and sedimentary rocks of
.,recambr1an
age in Mi.nnasota.
Clat:edlnd1r:ect.ly as being
These !:ocks have been
gran-
ol~er than the Saganaga
ita which 1n~rudes tbem (Schwartz, 1956, p.l) •
. An at:'tempt. was made to cief:e:mu.ne the age of
volcanics
directly by ~e Rb-St' method.
~e
For t~s
pu~ose one specimen of Ely 9reenstone.an~ ~oudan
shale have been. an,al~zed.
In addi~1on the
'rat.io of, c.alelt.e segreg~tlons
in ~e
bet.ween pillows
Sly greenstone was dete~ned.
This work is
~e
occurring
'sra7/sr86
present
not. cons:l.dered to be completed and
sUDDary' 1s in the nature
of a progress
repoX't.
Geoloqical
Summary.
The Bly greenstone consists of an assemblage of
lava flows, tuff
and I01nor basic
intrusives.
The
xocks axe fxe~ently al~ered to chlorite Bcblst. and
-234and h~ve been rec~Jstal1ized
contacts.
belts
near intrusive "igneous
The greenstone outcrops in disconnected
extend~ng from the Gunflint
west\"1ard tb~ough Vermilion
district,
On~ariO,
According to
~ake.
Goldich et. al •. (1961) the .Ely greenstone belongs to
~he Keewatin group and has been correlated
type Keewat1n~. volcanics
first described
w1th the
by Lawson
in 1888 near ~he Lake of the '~s.
The .Soudanforma~ion is composed .of al'terna't1ng
bands of ~hert and i~on oxides.
Ferruginous carbonates,
chlorite and sulfides also occur in small amounts.
Schwartz
(1956) considered
an upper member of the Ely greenstone.
(1961) prefer to give lot formational
The Keewatin volcanics
Gold1ch et ale
rank.
were intruded by the
Lau1t'ent1an gran1'tes one of which .i~ 'thfJ Saganaga
11'th on 'the Ontario - Minnesota border.
Saganaga
grani'te according
c1etemi~ed by Golcl1eh at:
to X-Ax' and
ale
(1961)~n
because
it:s age may actually
the Lauren~lan
bathe-
The ~ge of 'the
RbIDSr
ages
m1ea and feldspar
fram pegmat1tes 1s between 2.5 and 2.6 billion
~ver,
be
the soudan format:1onto
be ~reater
~an
granites "are believed
da~e the Algoman orogeny which tookpl~e
years.
this
to pre-
approximately
-2352.5 b111ion
years agoo
AccorCi1ngly, 'the age of the
01.50
R$ewatln volcanics
1nclua1ng the Ely 9reenstone
shouldvbs
greater than 2.5 billion years.
ZXPerirreental
Resul1:8.
Table 8.2 ,summarizes the analytical
reproduced in graphical
form in Plgure8.2.
assigned t.o the correQt~d
rubidium
dat:a which are
S7:87
/sr86
The errors
rat1'os and the
and 'stront1um analyses are estimates
xeproduc:ibi11ty.
Infomation
of the
regarding the locall1:1es
from which the samples ,were colleci:8Q ~e
given
in'
Chap~er 10.
Discussion.
'1'he,Elygreenstone
specimen has a sr87/sr86
of 0.8555 and a Rb/sr ratio of 1.45.
ly high for a basic
volcanic rock.
ratio
This is surprisingIts
s'tront:lum develop-
meni:iine intersects that of 'the upper mantle at '237S.:t
150 million years and sr87/sx86
The calcite
pillows
=
0.705.
occurs in font of narrow bands bei:ween
in an outcrop of 'the Ely Greenstone
at the C1t:y
lim1ts of Bly on 81ghway 21 enroute to, Babbitt.
not clear whether these s8gX8gat1ons
fo~
Ii: 1s
by pxecip1t:a-
t.1on from sea water at 'the time of eruption of the lava
-236-
....
0\
c-f 0
U)
N
&n\D
~O
~
~
•
....
0
e
~ 0
• •
00
+1
. -N
0
c
0
!
a.s
~~
g;
U)
N .. t
........
0
'ftl
e
&2
5
~
en
8
tN
0
~
C
to
8
r;;.
0
•co
~
en
ex)
G)
an
co.
\D
0
CD
Q
•
~
CD
s:(lJ
cf:
or4
~
CQ
.!
0
...
''8
• au0
.a.I
'10
~,
.... -H
i-J
lIS
='
'0
res
c
m
~~
M
+i
0
•
.-4
:5
rt)
an
;2.1
'tI
C)
Nlt
C'l)N
CD
~
\D
~
(X).
0\
...
0
0'
f"'f
•
pf
•
COt.4
tL1
~
~
....
CD
c
J.4
0
~
•
CO
N
NO
1""'0
..nf"'f
~
COO
r--
N
CD
+1
~
CD
I)
"'•
!! ...
Q
(\)
...
... cu
11
U3~
~
N
N
.s
c
Q)
5
~
f4
r:
0
\D
...s
~
'M
....
~
~
r-.
an
M
M'
Q4
..
...
r-
O)
tQ
~
+\
~
r--
\D
~
t-
• 0•
• 0•
.."
~
.......
an
&no
~
.e
0
fa.
~
'80
en
....0U1
s::
G)
~
C
...•
0\
en
0
t-
•
...>t
~
Sw
cw
res
CD
N
...
M
r--
•
....\0
~.
ti
~
~
~
:1;'
....tJ
co
ns
tI)
"r-
'" ...
C')
.....-
~
~
tJ
"
QJ
C't\
~
Ul
tf\
-237-
0.860
0.840
FIGURE
8.2
ELY GREENSTONE
AND
SOUDAN FORMATION
THE
0.820
0.800
Q780
0.760
UPPER
0.700
2
3
TIME
IN
BILLIONS
OF
YEARS
or whether
they age ths p:toduc't of later metamorphic
In any cae~ the
al'te~at1ons or hydE"othermal ac:tivi~y.
Sr87/sr86
that
ratio of the calcite' should be greater
of the lava at: the time of its
ing that the
small,
1:
=
Assum-'
Rblsr ratio in the calcite is negligibly'
an intersection
stone at
foxmatlon.
than'
1s ob'tained w1t:h the Bly green-
2300:t 125 million years.
The possibility
was introd~ced
into
cannot be excluded
that rubidium
the Ely 9%eanstone by metasomatism
solutions originat1ng fram'the
and hydro~he~al
Lauren~ian Int:r:usives.
In 'this c:asethe
age obtained
here dates the i:1ma of metasomatism and makes this
I'ock
unsw.~able for age deteminat.1on purposes.
The s~ronUum development linE» for
of 'the. Soudan fozmation
(1'1gure'S.2).
is plotted
An lntsJ:sact1on
ratios were identical
is not. necessarily
on 'the same diagram
with
wl'll have meaningful co-ord1natea
the 8pec.1men
the B.1y'9reenBto~
only 1£ their
a't the tiDa of deposition.
true.
0.68S.
the value
srS7/sr86 ratio at: 1:11epoint. 'of intersection
This
This
The SOUdanf()ZiDation gives
an age of 2700:t 250 wi'th the Sly greenstone,
of t.he
sz:87/sx86
almost: certainly
is
invalidates 'the age •. On
the other hand an intersac1:ion with the development
line for the upper mantle gives an age of approximately
1000 million
geological
This low age is contzoary to
years.
evidence.,
These d~screpancies
suggest that
the analytical data, for the Soudan formation are in
eJ:'ror.
Conclusions.
Theanalyt1cal
clusion
dat:a,ar8 consistent
r.
tha't the age of the Ely greenstone 1s 2375
150. This value, h~v,er,.
possibility
is suspect because of the
of metasomatic addition
..
Ely' greenst~ne
tian granites.
would make ~e
,pu~ses.
with the con-
of rubidium to the
at. t.ha time of intrusion
of 1;be Lauren-
This would lower the age value and
rock unsuitable for age dete~nat1on
A~cordin9 to Gold1ch et; al.
the Bly greenstone
is definitely
(1961) the age of
great.er than2.S'itb:Lllion
years.
The age of ~he Soudan fo~at1on, as 1nd1ea~ed by
the data, is incons1s~nt
both with geolog1ca~ evidence
and the abundances of stron~ium isotopes
as. they are
known at "'th,le date •. If . .'the ~ly 9re~nstone was enriched
in rubidium after
its
formation, the Soudan forma't1on
apparently was not. For 'this reason it may be more suitable for age determination pu~oses.
EVIDENCE OF SUB-CRUSTAL ORIGIN
OF ROCXtS
FROM THE MONTEREGIAN H1:LLS.
In1::r:oduction.
of strontium in four igneous
Isotop1c compositions
rocks from the fttOnteregian bills
of calc1'te
from a c:arbonatite
determined. 'the purpoDeof
demonstrate
a co-magmatic
and in one specimen
at Oka, Quebec, were
this investigation
was to
origin for the different
igneous rocks and the carbonat1te
occurrence at Oka
and to test t~e hypothesis that ~he parent magma was
de:lv~d from the upper mantle.
Geological
Summazy.
The Monteraglan
inent topograpbic
hills are a aer1es.of.e1ght
prom-
features extend~ng fxom Montreal
eastward across the St. Lawrencelowlands for a distance
of about. 50 miles.
'the centers of these bills
composed' of alka11-.rlch
igneous. rocks which collectively
consti~ute a distinct petrographic
one
of tile 1nt;rusives
ranging in campo~1tlon
are
province.
All but
consis~ of 'two or more rock types
from ultrabasic
and ..yamaski te to lni:ermediate
nepheline
and basic essex1~e
eyeni tea and
nordmarkitso
A campzehensive
of the 9aol~1cal
bibliog~aphy and a summary
information pertaining to the Mon'teregian
hills t1er~ given by Dresser and Danis (1944, po455~482).
Geological evidence sU9ges~ that the magma bodies
\\iers derived from
which ~ormed ~he individual intrusives
a common parent whose camposi~1on
diori'te~r
gabbro.
was that of an alkali
T"nemagmareservoir
to have been inside the Precambr1an
\\Jhich 1s believed
basement
was ~apped
1n several pliic'es and portions of ,:1. t were drawn off througb
pipes loc~ted al~ng. a fractu~e systeD?-which may ~
related
.1:0 the Appalachian orogeny.
s~ructural and Stratigraphic evidence ind1ca~eB a
post-Upper
Devonian age.
Osborne proposed a Tertiary
age on the basis of s1mtla:1tles
of pleochso1c
halos
surrounding crystals of zircon and t1~an1~e and those
developed
1944).
in 'l'erUary intrusives
Urry (1936, p.1221) reported
511:.'1.5 million
east
(Dresser and Denis,
years
of Mount Royal.
(LOwdon, 1960# p.38)
foX' a t1nguaite
The Geological
obtained
a Helium age of
sheet two miles
Survey of Can~da
an age of
122::t 9 m.y~ by
the K-Ar method using biotite
extracteCl from a nord-
markite
This ~ge be's been con-
from Broma Mountain.
firmed'by the Geochxonology
L~oratory at M.I.T.
(Eighth Anno prog_ Rep. 1960)0
rocks
The age of 'the igneous
of the l-iOntGE"eg1anhills is
therefoE"e
Cretaceous.
ExPer1men~al Results.
The experiment~l data are s~~ar1zed
and are shown in graphical
in ~able 8.3
form in Pigure 8.3.
The
errore ass1gn~d to the values of the rubidium and
strontium concentrations
as well as the corrected
sr87/sr:86 ratios are reasonable est1mai:es of the
reproducibility.
of
A description
the samples appears
in Chap~er 10.
Discussion.
The average value of the corrected arB7/sr86 ratio
of the essexi~,.
0.7049.
the yamaek1te and the. tinguate
is
This value is considerably lower than that for
However,
the nordmarkite which is 0.7156.
when the
s~~on~um development lines with ~e1r er~or 'envelopes
are plotted for 1:het norc1markite and the yamaski te , an
intersection
and
is obtained
.(sr8!ts:86)o
at t
=
11~:t.25 m111~onyears
= O.7947~ 0,_001.
This time is 1den1:i-
cal within exper1men~al ~rror to the age of the biotite
from Brame Mountain which was detexmined by 'the K-Ar
I
-243-
If&Q')
\00
MO
M
Ul
00
~
M
,
•
• •
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Ul
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NO
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e:
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pof
0
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+1
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0
al'
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a
pf
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ore0\'
tM
o
2
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to
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CD
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e-.
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cuttS
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~IG~
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• .... •
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-244-
to
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C\J
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I"-:
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--~~-- --i--- --=----
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V
metl1odo
'l:he ~ime at which the stxont1um development
lines 1ntersec.'t is 'therefore also the tirr..~ at t4hich
the diff'ereni: rock types wax-s separated
magmaand from each o'thar
radiogenic
from 'the paxen~
and began to accwnula:te
strontium 'in accordance with their different
Rb/sr xoat1os.
There is thus strong
evidence that ~e
nox:dmarkite is
a magmatic. differentiate
of tbe same
, parent magmawhich gave tise to 'the yamaski te and the
o~ber rock type.s.
The only way in whlch the nordma&"-
,kite could develop a sr87/sr86 gatio of 007156 i~ 115
million, years is 'to have. had an initial
O. 7047. , Had the no~ark1
'tEl ma~
ratio
of
been contaminated
at the i:1me of its 1ntzuslon w1'thold crustalnater1al •
. having a s-g87/szS6
~at10 much ~J:eater'than
0.7047, it
could not give an intersection with the'yainas1d.te at a
i:ime which is 'known 'to be 'the age
of
these
roclts from
.ot:her ev1denceo
The 's'rB7/srB6
ratio
: O.7047~ 0.001 •. This is
'
..
pared 'to 'the aveX'age
of the parent. magma was
suJ:px1s1ngly'low
sr87/sr86
rat100f
when com-
eleven Recent
.oceanic basal'ts which is 0.7012 (Chapter 6).
low abundance of.
This
sr87 indicates 'that the soUrce material
-24Gao
from which the magma wa~ fo~d
~lt1ng
by par~lal or complete
had a very low lUl/Sr ratio,
source ma~er1al
for average
oceanic
ratio of the scuJ:ce material
even lower ~an
'!'heRbISr
basalts.
can be estimated
by assum.
.'
inq an age of the eart:h of 4.5 billion
sra7/sr86
initial
The RbISr ratio
the
years and an
rat:Lo of O.10~4+ 0.002 (Chapter 1).
calculated
1n 'this way 1s O.022:t 0.011.
This value is so, low that only an ultrabaalc xock could
qua11fy
as a source for 1:he p:rimazy Monteregian
magma. If ,~e
content:
of alkali
bill
~lements decreases
downward in the upper' man~le, 'this would, 8ugges1: that
the source xeglon
fog the magma was at considerable
depth ,in ~he.upper man~le.
'The isotopic
concentrated
comPosition" of 'st.ront:lum in calcite
from Nb ore from the carbonati'te
Quebec, was de~em1ned
tium 1nthe
at Oka,
,foX' cempal"lson with the"st%'on-
igneous rocks of 'the Monteregian h1l1so
The .relationship
,of i:he carbonat.1te occuX'rences at
Oka to the intJ:U81ves of the Mon~ere91anbills
clear
ana the general quesUon of
bonatites
independent
:t 0.0005.
1s still
1s not.
the origin of car-
unanswez-ed. The 'average of two
detem1naUons
gave
sr87/sr86
1:1.
O. 7062
8,3
As can be seen in Figure -i t:beerrors
between
-247the carbonat1te
value and those of the essexite,
and yamask1te .overlap.
The
sr87/Sr86 ratio of ~he carbona-
t1te is noi: feeasurably different
igneous rocks.
from 'tha~ in the. basic
The resul'ts are 'therefore not inconsistent
with the conclusion
that the calcite of the carbona~ite
at Oka is. of magmatic
origin.
This conclusion
:La str~n9thened
a s~87/sr86 ratio of O.709~O.002
for Grenville
tinguaite
by comparison
with
reported by Gast (1960)
l1JQes1:one. An impure Grenville
11mes~ne
a small amo~nt o~ mica would give a much
containing
higher ratio.
Gast also
reported
a value of O.713:t
0.'003 for an Ordovician l1mestone from perry County,
Texas.
Conclusions.
'rhe' whole-rock Rb-Sr age for a nOJ:dmarkite from
Shefford
~
and a yamask1 te irem Ht:. Yamaska was found
115 t 25 11111100.ye~s.
detetm1ned
by
This. age 1s1c!entical
the. K-Ar method using
to
t:o. one
b1o~ot.e .'frOm
BrCme
Mount8iri •
.The
srS7/s~6
ratio
of
the paren1: .magma 115~ 2S
..
million
years' ago was .0.7047 :t..O.OOl 1~caUng
~hat. .the
-248-
source was sub-crustal.
the conclusions
~1e evidence
reach$d p:ev1oualy
presen~ed
confi~B
on the basis of
geologic evidence that the different
rock types are
products of magmatic dlfferen~1at1on of a common paren~
magma.
The unusually
magma in~icates
low
sr8~/sr86
ratio
of this
primary
that the source region had a lower
Rb/Sr ratio than that
~ouna
for continental basal~s,
suggesting an unusual depth of origin.
'l'be'1so1:op1c.
composition of stronUum
,from~e
car:bonatlte
in calc1~e
at Oka.1s compatible w1~ the con-
clusion that ~he calc1~e 1s of magmatic,
sub-crustal
origin and may be rela~ed to the igneous 1ni:ruslves of
the Cl:ea.
Cb.a'Qter 9.
VARIATiONS
sr86/sr88
OF THE
sr84fsr88
AND
r,
RATIOS.
Introduction.
,During the course of this investigation
96 strontium isotopE! ratio
fo~
determinations
a total of
have been per-
in ccoperaUon 'with C.C. Schne'tzler.
is composed. of 63 analyses of terrestrial
'!'he t;crt.al
rocks mos~ of
which are bas:Lc igneous rocks of sub-crustal origin,
25 tektite analyses
and 8 analyses ofa
The opportunity is therefore
srco3
standard.
given 1:0 compue the
..abundances of the non-radiogenic
in the three types of material
isotopes
of strontium
and to calculate
average
sr86/sr88 and sr84/sr88 ratios.
~rimental
Resul~s.
Most of the,
Bra6/ar8S
raUos
were calculated
frcm
. about 80 consecutive ..scans •. The reproduc1bl11 t:y ex-
pressed as t:hestandaXu deviation
istO.0006 ortO.5~.
(flable 9.1).
of a s1ngle' analysis
Duplicate runs on the
same' sample showed thai: i:hesr86/sz:88
ratio
c~
vaxy .by
-2S0cro>
as much as 0.0021
(1.8%) between
successive
the .samesample (Schnetzler ,T3990)
due to isotop1c
fractionation
0
analyses
of
'lhis variation
is
in 'the mass spactrometer.
~e sr84/sr88 zoatios are generally based on no
JQOre~han 12 to 18 scanso
ord~r oft
.,.st~dard
~e precision
0.0002 or 3.0% (~able 9.1)
deviation
error
is of the
expressed as ~e
for a ~1ngJ..e.analysis •. This ratio
was found to.vary.by as much as 0.0001 .(1%) between
successive
analyses
of the same sample
(Faure R1292,
~chnetzler T3986).
Average values of 'the
sr86/sr88
and the sr84/sx8B
raUos were.calculaUKJ for each of the three types of
material
as well as for all analyses combined (Table
9.1).
Table 9.1 AVerage.sr86/s:8B ,and sr84/sr8B
sr86(sx88
Ha'terial
sr~3
0.1195
a:
:t: 0.00018
<r
'1:. 0.0005
O.la192
.. ~kt.1t:e8
:t 0.00015
::t 0.00077
TeZ'%8strlal
Rocks.
C!?
cr
Comb1rtedAverag9
0:
.(j
0.1190
sr8~/sr88
0.0066(7)
2S
.' 0.0066(55)
63
.:t. 0.00055
:0.0002'
:t 0.0006
8
. 0.0068(18)
% 0.00006
1:0.00023
.:to.00003
0•.1191
No.of Analyses.
:t 0.0001
:t0.00027
:to 0.00007
Or 0.00006
hUos.
0.0066(80)
:0.00003
~0.0002
96
-251-
No. I
2
.1180
.1182
.1184 .1186 .1188
.1190 .1192
No.2
2
SrC03
(8
ANALYSES)
.1194 .1196 .1198
.1200
.1202
.1204
86 88
Sr/Sr
TEKTITES
(25
ANALYSES)
II
.1175
.1180
.1182
.1184
.1186 .1188
.1190 .1192
.1194
.1196 .1198 .1200
.1202
.1204
10
S8r~B~
No.3
IGNEOUS AND 3
SEDIMENTARY
ROCKS.
8
)-
(63
°6
z
w
ANALYSES)
=>4
0
w
0::2
lL
.1180 .1182
.1184 .1186 .1188
.1190
.1192
.1194 .1196
.1198 .1200 .1202
.1204
86 88
Sr/Sr
No.4
IGNEOUS a SEDIMENTARY (3)
ROCKS. TEKTITES, AND SrC03.
12
10
(96
ANALYSES)
)-
°8
z
l&I
•
=>6
o
l&I
.1208
0::4
lL
2
.1180
.1182 .1184
FIGURE
9.1
.1186
.1188
.1190 .1192
DISTRIBUTION
OF
.1194
86
Sr/Sr
.1196 .1198
88
.1200 .1202
RATIOS.
.1204
86 88
Sr/Sr
Discussion of Raeults~
In o~der to s~udy the distribution of values of ~le
sr86/Sg88 ratio in i:be th:8:'eetYPsa ~f ma'ter1al, a ,aezies
of histograms was construc~ed (Pigure 9.1).
of analyses
The numbe~
of the srC03 and the 'tektites is not tBuff!1-
ciant to show a distinct distribution patterno
.analyses of the igneous
dency toward a nomal
r001(3,
The
however, do show a i:an-
distribution.
The high frequency
of values in the range from .1184 to 01187 is striking
but is not considered ~o be significant.
An examina-
tion of the da~a shows t.ha;t no one rock type favours
this particular
this
range.
is an instrumental
It
is t:herefore suggas'ted that.
effect
and is due to the fact
that a large number of a.nalyses \~as made during a
pexiod of time when fractionation
processes
spectrometer favoured this range of values.
in the mass
The fluct-
uations in the measuremen1: of the sr86/Sr88 ratios are
well displayed by sample R1292 (Chapter 5, 'table 5.1)
and the
sreo]
sUlldard
(Chapter 5, Table 5.2).
All 96 analyses are combined in h1stogxam number 4,
Pigure 9.1.
A
normal distribution
same mean and standard
deviation
curve having the
was fi ~tad to the
h1stogxamo
The goodness o~ fit was tested by replo~tin9
the dat:a on normal probability
performing
paper
(Figure 9.2)
a c:hl'square test.
The plot on the probability
graph allows some ev1-
Qence of the presence of ~wo superimposed no~al
bu1:1ons.
and by
However, as mentioned before,
to instrumental
isotope
fractionation
this
d1stri~
is ascribed
effects.
More data
taken over a period of time would be needed to confirm the
existence 'of two normal populat1ons.
A
single
line can be fitted to the pOints indicating
overall. distribution
A chi square
is approximately
one.
to detexm1nC! the
gOodness of fit of the data to a nomal
I
that the
a no~al
tes't was performed
straight
dist.ribution
.
(Dixon and Massey, 1951 ~ p.221).
Thestatistic
used is
defined as
where
k
II
number
of ca1:egories
£1
=
observed fre~ency
p1
=
for each ca~egory
~eore't:l.cal. frequency for each category
assuming no~al distribution •
.Values of Pi are obtained by calculating
'the normal distribution
the areas under
curve between the l1m1'1:sfor each
-254-
CUM.
0/0
FIGURE 9.2
PLOT OF CUMULATIVE
DISTRIBUTION
OF THE S~'S~8 RATIOS
98
ON NORMAL - PROBABI LITY
95
PAPER.
90
80
70
30
7
20
o
0/
/
10
/
/
/
0//0
5
/
/
/
0/
2
.1182
.1184
.1186
.1188
.1190
86 88
SrlSt
.1192
.1194
.1196
.1198
-255-
Of,it P-are
'rhea1str1butiom
categozoyo
ant; degrees
of freedomo
~e
tabulated
fox: differ-
number of da9xoses of freedom
is determined by
d~
=
(lc-l)
- number of assumpt1ons:o
Since the meoan and ~he standardodev!a~lonfor
of .data mus't be knOWn before
dof
=
Pi °can°be calculated,
k-3.
It. is" cusi:omaEY to accept: the hypothesis
'tribution
a given set
"
is n~mal when 'the calculated
less titan l.tsopredlct.ed
that
a g1ven die-
value of
value at t.he 9~
X
3-
1s
confidence limit.
~
The value of ~
.
"
for the distri~t1on
of the
sr86/sr88
ratios 1s 15.50 ("able 9.2). Since ~b1s 1s less than 18.31
t.he hypothesis
for 10 deg1t'8ssof freedom,
tba~ th~ d1s'trl-
but:1on1s nomal is accepted at the 9!?"confidence lim1t
(D1xonand Massey, 1957, Table A-62°,
" '---v-
p.385).
"The average"oyalue of 'the sx86/Sz88 ratio
for the
entire" assemblage of" 96 analyses ls0.1191,cr-~ 0.0001,"
q-. % .. 0.0006.
"The spread of °tile dlst:w:1but1on
o
1s suell
tha~
0
~11
previously reported averages .(Chap~~ 3, Table
3.1) as
~ ,,,""
..
o
"
well as" tbe averages for "tbe'tbree
ponedhexe
fall
0
types of ma1:erlal re-
into t:he band O.1191:t 0.0006 «T) at the
68% confidence l1m1t.
'lite difference between the previous-
lYoaccep~edvalue" for t~e sr86/sr88 ofoO~1194 and the
-256-
Table 902
Chi SquaX'e Teat
Fi
Inte~al
(Ft-fi)2
£1
.!!i--fi) 2
Pi
.1180
3.2
1
4.84
1.51
.1180 - .1182
.1182 - .1184
3 ..2
3.24
1.01
5.2
5
~:i7
3.24
0062
.1184 - .1186
.1186 - •118a
.118a ...•1190
7G8
14
38.44
4.93
10.2
12.0
12.7
15
9
23.04
900
11
2.89
12.0
6
36.00
2.26
0.75
0.23
3.00
10.2
8
4.84
0047
7.8
5.2
3.2
.,
7
0.64
0.08
0862
3
3.24
0.04
3.2
3
0.04
95.9
96
.1190 - .1192'
.1192 - .1194
.1194 .- .1196
.1196 - .1198
01198 - .1200
.1200 - .1202
.1202
Totals
15.50
overall aveX-age obta1n~dhere i.a statistically
flcant.
0.01
0.01
not 81.;01.•
This conclusion is conflxmedby c.ompar1ng
mean reported
by Ald:r;1c:hat ale (1953)
the
to the average
re,ported here •
.1l1dr1ch et: al
'!'his work _
D
0.0004.0i>
=
'(1953)
CII
I
sr86/sr88
ar86/sr88
% 0.00032 •.
Since
=
O.119S:t 0410003(0=)
a O.1191:tO.0001(~)
D < 2. <rbJ
'the 'tWomeans are ident.1cal at. the 95" confidence
limi~.
Because the difference between 0.1194 and 0.1191 is not
statistically
significant,
or 'modify 'the fo~!:
value.
values of the sr$1/srSS ratio
The distr1butionof
is shownin Figure 9.3.
standard deviation
,The means is 0.0066 with Cl
of 0.0002 (cr).
fitted to 'the histogram
fit was obtained.
b111ty paper
there is no reason to %eject
normal curve was
A
(Figure 9.3) &nd a satisfactory
The data were also plotted on proba-
(Figure 9.4).
approXimate a stra19h~
, ~at: i:he distribution
The experimental
line
quite
well
thUB
points
confixm1ng
is normal.
Conclusions.
1..t...
The distribu1:ion
of
the
measurements of the sz:S6/srS8
is no:r:malabout: ~e mean at the 95%confidence limit.
The average for the total
of 96 analyses is 0.1191,
-
Because of
+
'
0-.:= - 0.0001,<:1- Z 0.0006.
the da~,
indicated
the large
spread of
by a s$;andard dev1at.1on of :t.O.OOQ6«01l.
this value is not significan~ly different. from tite prev10usly accepted value of 0.1194 (Nier. 1938) or 0.1195
(Aldrich et al., 1953).
The meaBu~nts
nomally
of ~e
sr84/sr88 xatlos are likewise
dlstr1bu<ted abou't the mean of 0.0066,0:. :! 0.00003,
-258-
14
12
>-
10
(.)
Z8
I&J
:)6
a
1&J4
a:
u..
2
.0060
.0062 .0064.0066 .0068 .0070 .0072
84 88
SrlSr
FIGURE 9.3
DISTRIBUTION
OF S8r1S~8
RATIOS IN ROCKS TEKTITES
AND StC03
(80
ANALYSES)
-259-
CUM.
°/.
99
FIGURE 9.4
98
PLOT OF CUMULATIVE
DISTRIBUTION
OF
S~iS~8 RATIOS
95
90
80
70
60
50
40
30
20
10
5
2
.0060
.0062
.0064
.0066
84/ 88
5 .. Sr
.0068
.0070
.0072
-260-
O-='~ 000002, which 1s ,identical
to the values
previously
reported by Nier (1938) and Aldrich at al. (1953).
Ev~n though the distribution ofthemeasuremants
1s
appZ'oximatelynormal, the wide spread of 'the .d~ta require's
a large number of 1nd1v~dua~ mea~urements before a sta~!st1cally reliable mean is obtained.
-261-
DESCRIPTXONOP
Oceanic
S~~LES.
Basalt:s
R1292 . Olivine basalt
Aphanitic: 'to glassy, highly ves1cular,almost
.a pumice. Scattered phenOcrysts of olivine.
Erupted in 1894, Kilauea, Hawaii. Collected
by N.E.~. Hinds near Postal Cavern.
R1282
Basalt glass
Glassy, highly vesicular with bubbly surface
indicating top of flow. probably erupted in
1921, K11aue~, Hawaii.
R2001
Olivine basalt.
Glassy, higbly vesicular, containing sca~tered
phenocryst.s of, olivine.
Recent: flow on floor
of Kilauea sink (Birch #20).
Rl993
. Basalt
Apbanit:l.c•. ves1cular, no olivine
observed.
R2002
Mauna Kea, Hawaii
phenocrys~s
(Bircb
#H63).
Basalt:.
Pine grained, composed of plagioclase and
pyroxene. No 'olivine observed. Maui Island,
Hawaii (Birch *858). '
~2029
Oliv1nebaeal~
Aphanitic, ..vesicular w1~h sca~~red phenocryst.s
of olivine ..Tu.t.uila, Samoa.
(Birch #2594).
RiggS
Olivine gabbro
.Medium.
grained, containing euhedral phenocrysts
of olivine.
Volcanic neck on .Ofu Island, Samoa
(Birch 12661).
-262."...'
R2030
Basalt
Aphanitic, ves1cul~r wi~hout obsegv~le olivine
phenocrysts. Ofu Island, Samoa (Birch ~2651).
R2031
Basalt
Aphan:l.t1c, vesicular
clase.
R4125
Ascellsion
with phenocrysts' of plagio-
Island'
(Blz.ch *2751).
Basalt
Aphanitic
and slightly
VG$iculax.
Mid-1\tlantic
Ridge Lat. '31~18.'8N, LO~9. 40Q 54.'3W.
Collected
"rift- f~
sloping bot~om.at depth
in
of about. 1250 meters." Bcho' sounding traces
ava11~le
from Capt:. Cous'te'au'. Gift: of Lloyd
Breslau, 1960.
R4156
Ollvinebasalt
Horta Payal, Azores.
M.I.T. Pe~rology Collection
«"6412.
R41S8
Obsidian
San Miguel, Azores.
#6410
Continental
R4161
Petrology collection'
H.I.T.
Volcanic Rocks
Hypersthene, augite andesite (bomb)
Pine grained, composed of plagioclase
and pyxoxene.
Erupted in 1909 at: Sakurajima, Kyosho, Japan.
M.I.T. Petrology .collec~:Lon. #2081 •. Collected by
Sidney Powers,
R4221
1915.'
.
Andesite v1'trophyn
Contains
hypersthene and augate •......
~rupU!a.1n 1914
at Sakurajima', Kyosho., .Ja~an.."q . M~I~'1'
•. Petrology
Collection #2082 •. COllectetl by Sidney.powers,
1915.
R4244
Dacite
Light. grey,
fine grained,
pyroxene .and
quartz.
cOmposedof plagioclase,
El'Upted in
1888.81: aandai
San, Japan. H.I.'1'. Petrology Collection
Collected by Sidney Powers, 1915•.
#2079.'
..
R1864
Basalt
samples from bore holes for KCgna ~1ver Project,
Bombay State •. Mapsheet No.47, Gill and 15,
between Pophal1 (17026 N, 73046°E).
El.2000(M.S.L.)60/922.
t
R186S
Basalt
.Same as above.
B.H.TS, El.978°(M.S.L.)60/937.
R1868
Basalt
Same as above.
B.H.T4, Elo1811'(M.S.L.)60/949.
R1428
Basalt
Aphanitic,
slightly vesicular.
P.M. Hurley and R.lj.
Trail
ate. u.s.
Fairbairn
B.H.T4B,
Collected by
.along Wahkeenah
30 jusi: east of Portland,
Ore90~..
Samples from flow cen'ters only, starting at t.op,.~.
of stratigraphic section of about 1000 fee't.
1U435
Sasalt
Aphanitic, slightly vesicular.
No minerals
identifiable.' Same as fo: R1428.
R1443
Basal~
Aphani~ic:, sllghtly. vesicular.
Same as for
R142Bo Bottom of s~ra~lgraph1c sac~lon.
R4209
Diabase
Pine grained, composedof plagioclase and
pyroxene.
cliffe
R4210
Palisades Inb!rs~ate Park, 'top of
Diaba~~
pa~1sades Interst~te. '1'ouriB~ Camp, 100. f~.
Hudson River.
R4211
Diabase.
Sleeping Giant Quarzy, .Mt. Camel,
Haven, Connec:Ucut.
R4159
above
north
of New
Olivine basalt
Vesicular, apban1't1c: wi'th olivine phenocrys1;s.
Post-Pleistocene ~n.age, Iceland, from M.Z.T.
petrology Collec~1on.
R4243
R1574
R4245
Taehy11~e (basalt glass)
Glassy, scorlaceous flow surface.
I~aly, M.I.T. Petrology Collection
Mt. Vesuvius,
i459.
Basalt
Aphanitic, ves.icular, Yellowstone Park.
Basalt
Tert1ary age, SquawCreek, Montana.
M.I.T.
Petrology Co~lection #4805.
Precambrian Basic Xn~rusives
R4193
Anorthosite,
with shaxpbands
of ensi:at1te
Wa~erkop 602, Bushveld complex, Shaler Memorial
Expedi1:ion.
Harvard #13444x.
Donated by
Dr. J.B. ~ompson.
R4194
Norit:e
Mosego Mountain, Buehveld comp~ex, Hackney 700,
Shaler Mem. Expedition.
Rarvazd #13434x. Donate~
by Dr. J.B. Thompson.
R4195
Pyroxenit.e - overlying cbz:onl'teband
Mooihoek
147, Bushveld Complex,
Donat.ed by Dr.
R1231
J.B.
Harvard #13452x.
Thompson.
Gabbro (Duluth Gabbro Complex)
Eight dnu.les south of bridge at Zsland - orchard
Lake, west: siae of Rte. 4, Minnesota.
Specimen
'taken 6- below glacialsuxface.
R4l86
Anortho81~e
Stillwater complex, Montana.
MontereQ1an 81119
R4i79
Yam~s1dte
Mt:. Yamaska, .Quebec.
1960.
Collected
by G.R. Beall,
-265-
R4180
Essex1te
f4t. Johnson,
OUebec •. Collected
by G.B. Beall,
1960•
.R4181
Nordmarkite
Shefford, Quebec. Collected by G.R. Beall,
1960.
R3069
T1ngua1te (1)
. St.
R3253
Joseph's. Boulevard,
Montreal Eas't, Quebec.
Carbonatite.
Ore grade Nb. concentration.
Collected by J.A. Gower.
C3253
R3111
Oka, OUsbec.
Calcite concentrate prepared from R3253 by
means of Frantz Isodynamic Separator.
Bet~er
. ~ha~95" pure calcite.
Eclogite
composed of pyroxene and gaxne~. Entire sample
ground up, no. hand specimen available.
Inclusion
in kimberlite pipe, Robert Victor Mine, S. Africa.
Given by F. B1J:ch.
P3111
Pyxoxene concentrated
G3111
Garnet concentrated
Keew&t1ft-.Volcan1cs
from
R3357A. Chlorite'schist'
framR3111.
from R3111.
M1nnesot:a
(Bly gre8ns~one) .
Dark' Green•. Bntire specimen w~s cxushed.
COllected
by P.M. Hu'rley, 1956, at SOudan Mine, Vermilion
Range, Minnesota •. Geological SOc:Le~y of America
Pield Trip Guldebook~ Precambrian of Northeastern
Minnesota, p.100.
-266-
R3358B
Qsaenatone (Ely greenstone)
Pl.llegreen, not schistose. Contains calcite
occurring in t1:lin bands between .pillo\nJs.
Collected by P.M. Hurley, 1956, at City limits
of
Sly
on
B1g1tway 21
enroute ''to
Babbi1:t.
GoS.A.
Guidebook 1956, p.104.
C3358B
C~cite leached out of R3358B by means of O.SoN.
vycor-dis~illtad hydrochloric acid.
R3354
Shale or fine tuffaceous sed1men~
Soudan foxmatlon.
Collttcted at Soudan Mine,
Venti110n Range, M1nnesota by P.M. Hurley,
G.S.A. Guldebook 1956, p.9S.
1956.
,Shale composites
R4184
composl~e of App~lac~an shales of Paleozo1c age.
S~le~
WSES col1ec~ed from exposures of, shale of
pennsylvania '.tUrnpikegoing east from Harrisburg_
Thickness of individual
shale beds used 'to weigbt
proportions of samples in the composite.
by
prepared
Jul1anPe1ss.
R4l85
composite of Paleozoic shales from the west coast.
Prepared by Pe1s8 in same way as described above.
'R4132
Gneiss
Labrador trough,' eas'tem gneiss, zone B. Unconformably underlying tueUmoJ:phozed trough sediments.
Collected byPierxe Sauveo (8-42-57) fxom 58°15°5,
69014°W. ,
.,,267-
BIBLIOORAPh.~
Aldrich, L.T •• L.F. Herzog, W.K. Holyk, F~B. Whiting and
L.F. Ahrens, 1953, variations in isotopic abundances
of strontium" Physo Rev., 89, 631-632.
Aldx:1cb, L.T.,
LoP. HeJ:zf?9, J.B'o Doak and G.L. Davia"
1953, Va:iations 1n stgont1umlso~ope
abundances
in ~nerals, p~rt I, mass spectrometric analysis
of mineral sources of ,stront.ium, Trans. Am. Geophys.
Union, 34, 457-460.
Ahrens, L.R., 1948, The geochemistry of radiogenic
tium', Mineral. Mag., ,28, 277-295 •
stron-
.nhrens, L.R., 1949. Measuring g8010g1c time by 'the strontium'method, Bull. Geol. Soc. Am., 60, 217-266 •
W.R. Pinson, M.M. ltearns., '1952, AssociaUon
rub1d1um'~d potassium and their abundance in
commonigneous r~ks and meteorites,
Geoch1m. et
Cosmocb1m.Acta, 2, 229-242.'
.Ahrens, L.F.',
of
Backus, MoM., 1952, Mass spectrometric
deteEmination
of
the rela~1ve isotope abundances of calcium and ~e
determination o~ geologic age, Ph.D. 'thesis, Dept:.
of Geology and Geophysics, H.I.T.
BelouBsOv, V.Vo, 1960, Develcpmen~ of the earth ,and
tectonogenesis,
J. Geopbys. Research,
65, po4127.
Birch, P., 1952, Elasticity and const:1~ut.1on of 'the
eartil's interior, J. Geophys. Research, 57, 227-286.
~rch,
F., 1958, Differentiation of the mantle, Bull.
Gaol. Soc. Am., 69, 483-486.
Bowen, N.L., 1945, Phase equilibria bearing on 'the origin
ana differen'tlat1on of alkaline rocks, Am. J. 8c1.,
243A (Daly volume), 75-89.
Bowen# N.L.,
1948, The, 9~ani'te
of multiple prejudices,
soc.
])mo,
problem
and the me'thod
in Origin of granite, Gaolo
Ment. 28.
fil.J. and A.A. Smales, 1957, The determination
of
rubidium and caesium in' rocks, m1narals and mei:eoZ'ites
by neutron activation analy~1s, The Analyst, 82,
Cabell,
.---:=:--
390-460.
F. W. and H.S. liasbing1:0n, 1922, The average chemlcal composition of ~9neous %'OC1(6, Proc. Natl. ,Acad.
Sc1"U.S., 8, p.10S.
Clarks,
Clarke,
F.W., 1924, The dat.a of geochemistry,
U.S'. Geol
Survey Bull. 770.
Clarke"
F.W. and H.S. liash1ngton"
of the earth's
Paper
crust;
u.s.
-
1924, The composition
Gaol. Survey, Prof.
127~
Cormier, R.P., 1952, Rubidium-strontium
ages of,glaucon1te
and their application t;othe'construc:t1onof
an
absolub!post:.,precawrlan i:1me scale, Ph.D. thesis,
Dep~. of Geology and Geophysi.cs, M.I.T.
COJ:Z'ens,CoW.,
1948, Die geOChem1sche
B1lanz,
Na1:urw1ssen-.
schaft, 35, 7~12.
Demin, AoM. and D.No Rhitarov,
1958, Geochemie1:xy of It, Rb,
and III applied. to problems of 'petrology,
Geochemistry,
6, 570-581.
Dixon" w. J. and P.J. Massey, '!'X:., 1951,' Introduction
.statistical
analysis,
,McGra,,*-Hill, New Yo.rko
Dresser,
J.A'. and'T'.C.
Denis,
1944, Geol~jy
to
of Quebec.
Geoiog1eal Report 20, J>escr1pt1ve Geology" Depa:r:tment
of Nines,
Bngelhardt,
province,
Wolfvon,
of Quebec.
19,36, Dle Geochemie des Bar1UlUB,
Chemie der Exda, 10, p.1S7.
Ewald, H., S. GaJ;be and P. Nay, 1956, Die Isotopenzusammen-
se~zun9 von'Strontium aus M$srwasser und as rub1d1umaxmen gestelnen.
~. Naturforschg.
11a, 521-522.
-
-269-
Evans,
R.D.,
1955, 'I'he atomic::. nucleus,
McGraw-Hill
New York, N.Y.
H.W., L.B. Ahrens ana LeG. Gorfinkle, 1953,
Minor element content of Ontario diabase, Geochim.
et comnoeh1m. Ac~a. 3, 34-4~o
Fairbairn,
Faul, H. (SQ.), 1954, Nuclear geology, Wiley and Sons,
In.,
Naw York, N.Y.
Fleischer, M., 1953, Recent. estimates of the ~undances
of the elements J.n the oarthOs crust, u.s. Geol.
Survey, Circular 285.
Plynn, K.F. and L.B. Glendenin,
1959, Half-life
and beta
spect:rum of Jtb87, Phys. Rev•• 116, 744-'148.
Gas't, P.W., 1955, ~bundance of sr87 during geologic
Bull. Gaol. Soc. Am., 66, 1449-1453.
time,
Gast, P.W., 1960a, Limii;a1:ions on the, composit.1on of the
upper mantle. J. Geophys. Research, 65, p.1287.
Gast, P.w., 1960b" ~lka11 metals in stone meteorites,
Geocb1m. et Cosmochim.
Acta, 19, 1-5.
Golciberg,,!:.D. and G.O.S. Arrhenius, 1958, Chemistry of
pae1f1cpelagic
sediments, Geochim. etCosmoehim.
Acta, 13, p.1S3.
Golaich,
S.S., A.O. Hier, Ho 8aaasgaard, J.B. Hoffman
and H.W. Kl'ueger, 1961. The Precambrian geology and
geochronology of Minnesota, Bull. Minn. Geol.
Survey 41.
Goldschmidt, V.M.,' 1933, Grundlagen der quantlt:at1ven
Geochem1e,Portsc:hrlt~e
17, 112-156.
d. Min., Krist.
Goldschmidt, V.M., 1937, The principles
u. Petrogr.,
of distribution
of chemical elmuents in minerals and rocks, J. ChemD
Soc., 655-673.
-270-
Goldschmidt,
V.M.,
1954,
ed. by Ao Muir,
Geochemi~'try,
Oxford a.t 'theClarendon Press.
Graf, D.L., 1960, Geochemtstryof
carbonate
sed1man~s
and
sedimentaxy carbonate rocks, Geo1. Suney Illinois,
Circ. 297,.. 298. 301, 308, 309.
Green, Jack and Axle Poldexvaart,
fields
and trends,
1958; Petrochemical
Geochlm. et Cosmochim. Acta,
13, 87-122.
Handbook of Chemtstry and Physics, 1951-1952, C.D. HOdgman
ed. in cb1ef,33zd.
ed1t::Lon,
Chemical Rubber Publish ..
ing co., Cleveland, Ohio.
Harns, P.G. and J.A. Rowell, 1960, Some geocbem1cal
aspects of .the Mohorovicic D.1scontinui t:y , J. Geophys
Research, 65, 2443-2460.
/I
1960, Measuremen't of potassium, rubidium and
strontium, in eighth annual progress :epon: for
Hal't. S.R.,
1960, A.E.C. Contract AT (30-1) - 1381.
Heide,
F. and W. Christ.,
tiums und Bariums,
1953, Zur Geochemie des St.ronChemie del: Erde,' 16, 327-330.
---
Herzog, L.P., LoT. Aldrich, W.K. Rolyk, I'.B. Whiting and
L.B. 1tbrens, 1953, Variations
in 8~ronUum iso~pe
abundances in minerals,
ltadiQCJenic Sr87 in
pari: II.
biotite, feldspar and celestite.
Union, 34, 461-470 •.
TZOBns.
Am. Geopbys.
W.B. P1nso~ Jr., 1956, Rb/Sr age, elemen'tal
and 1e~op1c abund~ce st.udies of stony met.eoJ:1tes,
Am. J. Sct •., 254, 555-566.
Herzog, L.P.
Herzog, LoP.,
.
ana
W.R. Pinson
Jr.
and R.P.
Cormier,
1958,
Sediment age deteXm1nat.ion by ~/sZ" analysis of
glaucon1~e, Bull. Am. Assoc. Pe~roleum Geologists,
42, 717-733 •
..
Hevesy. G.V. and K. WUrstlln,
des Stront1ums,
•
.
1934, Vber die Haufigke1t.
z. Ano~g •.Allgem.
Chem., 216. p.312.
-271-
Holmes, Ao,
1932, The origin.
o~ igneous
rocks,
Gaol.
Magazine, 69, po 550.
Horstman, E.L~f 1957, The dis~r1bu't1on
rubidium,
and caesium
in igneous
roc~s, Geochim. etCosmochim.
of
11t;hlum,
and sedimentary
--
Acta, 12, 1-28.
Burley, P.M., 1957, Test on the P9ss1ble chondrlt1c
~amposlt1on of the earth's mantle and its abun:dance o~ uranium,
Gaol.
Soc.
thorium
and potassium,
Bull.
Am., '68, 379-382~
-
Ka~chenkov, S.M. and E.I. Plegontova, 1958, Minor elements in the basement: rocks of the eastern part. of
'tbe,Russian"platfom,
GeOc:heitdst:ry, 2, p.224.
G.e.,
Kennedy,
r
1959,The
Qz:ig1n of conUnents,
mountain
ranges,.and ocean basins, .Am. Sc1ent1B~,47,
"
"
491-504.
Ruenen, Ph.H.,
1941, Gecchem1eal calculations
concernin the total mass of sediments in ti\e earth, Am.
J. Sei., ~39, 161-190.
Kuenen, Ph.B., 1946, Rate and mass of deep-sea
ment~Uon,
Am. J.
Se1'.,
sedl-
244, 563-572.
Lovering, J.P.,
1958, 'lhe nature oithe
Mohorovicic
discontlnu11:y,'tzoans.
Am. Geophys .• Un10n,' 39,
p.947.
Lowdon. J.A.
(ed.) , 19~O, 'Age determina'tions
Geological Su~y
by the
of Canada, Report: 1, Isotopic
Ages, Paper 60-17 •.
MacDonald,G.J
•.P •• 1959, ChondrLt;es and .'the chemical
ccaiposltlon d!, the earth, in Researches in Geo-
chemistry,
. Inc.,
Dew
P.R. Abelson ed.,
John wiley and Sons,
York, N.Y.
MacDonald, G.J.F.
and N.P •. Nesa,
transitions
with1n 'the ear~,
65,2173-2190.
'j
StabiUty of phase
J.Geophys. Research,
1960,
-272-
Machado, Jr., 1958, Compress1bil:Lty and 'tempezoatura in the
earth°e interior, Trans. Am. Geophys. Union, 39,
p. 943.
Mason
#
B., 1952, Principles of Geoche~stry,
John Wiley
and Sons,. Inc., New York, N.Y.
Mead, W.J.,
1914, The average igneous
rock,
J. Gaol.,
22,
p.772.
Nicolaysen,
L.O., J.W.L. de Vi~liers,' A.J. Burger and
Strelow, 1958., New measurements re~ating to
P.li.E.
the absolute age of the Transvaal System and the
Bushveld Igneous Complex, Trans.
Geol. Soc. S.
Africa, 61,137~163.
Nier, A.O., 1938, Isotopic constitution
'1'1, and 89, Phys.• Rev.,
Nockolds,
S.R. and R.L.
of Sr, Ba, Bi.
54, 275-278.
M1~chel1,
19~.
The geochem1s1:ry
rOCks, a study in the
the major and trace elements
o~ some Ca11don1an'plutonlc
relationship be~en
of igneous rocks and their minerals. Trans. Roy.
Soc. Bdl~urgh, 61, 535-75.
Nockolds, S.R. and R. Allen,
some igneous rock series,'
Acta, 4,.p.10S.
Nockolds, S.R. and R. Allen,
same ~gneous reek series,
Acta, 5, p.24S.
1953, The geochem18.~ry of
I.,
Geoch1m. et Cosmoeh1m.
1954, The geochem1st.ry of
II,
Geochim. et Cosmochlm.
Nockolds, S.R., 1954, Average chemical compositions of
.some igneous rocks,
Sull.
0801. Soc. Am.,
65,
1007-1032.
Nockolds, S.R. and R. Allen,
some igneous ~ock series,
Acta, 9, p.34.
Noll,
1956, The geocbemistry
III,
of
Geochim. et Cosmoch1mo
W.,
1934,' Geochem1e des Stront1ums, M11:Bemer'kuDgen
zur Geochem1e des Beriums, Chem1e del' Brde, 8, p. 507
0
-
-273Odum~ H.'1'o, 1951a, ~otes on the stZ'ontlum con'ten'tof sea
water. celestite, rad101a:1a and strontianite snail
shells, Science, 114, p.211.
Odum, H.'!'•• 1951b,
The stability of the world
e1:rontium
cycle, Scien~, 114, p.407.
Oftedahl,
.
, oxes,
,
c.,
19Se, A ~heory of exbala~1ve-sec1i_ntary
...
Geolog:Lska Po~en1ngen~ X Stockholm
'Forhand11ngax, 8Q,1-19.
Claire, 1956, Age of me~eor1tes and the eazoth,
Geochim., e~ Cosmochim. Acta, 10, 230-237.
Patterson"
Pecora, W.T., 1956, Carbona'tltes,
Soc~ 'Am'., 67, 1537-56.
a xev1ew, Bull.
Pinson, W.R., L.B. Ahrens and M.L. Pranck,
Geol.
1953, The
abundances of .L1•. Sc, Sr.
B~ and Zr 1n chondri ~es
and ,some ultramaf1crocks,
Act.a••. 4, 251-260.
Geoch1m. et Cosmochim.'
Pinson" W.B •• L.P. Herzog, P.A. 1\n~erson and R.P. Cormier,
1957, Rb.Sr. Ca, and It contents
and 'the isotopic
re1aUve abundanCes of Ca and Br in a sea water
sample, abstrac~, Bu~l. Geol.'Soc. Am., 68, p.1782.
Pinson, W.R. and Schnetzle:,
C.C•• 1960, Rb-Sr age study
of 'tektites,
Eighth Annual progr. ~ept. for 1960,
A.E.C. Con~rac~
•
. AT(30-1)-1381
Pinson, W.R •• 1960, Sources of error 1n the p~eparat1on
of spike and shelf solutions for geocbronametric
w~J:k, Eighth,Annual ,r09.' Rept. for 1960, A"B.Ce
contrac~ AT(30~1)-1381.
i»olc!ervaarl, A •• 1955. Chemistry of, the earth's
crost,
in Geol. soc.• Am., Special Paper 62.
Ramberg, 8., 1956. pegmai:i~s
Gool. Soc. ~.,
in
westem
Greenland,
67. 185-214.
Rankama, K. and 'l'h.G. Sahama, 1950" Geochemistry,
Univers1ty
Bull.
of Chicago Press.
'rile
-
R1n~~od, A.E., 19S5, ~e princ1plesgoverning ~race
elemen~ d1stx1but1on during magma~lc crystalliza~ion,
Geochim. st
Cosmoch1m. Acta,
7, pela9.
Ross, c.s., H.D. Poster an~ A.T. Meyers, 1954, Origin of
dun1~es and olivine rieh inclusions in basaltic roCks,
Am. Mlneralog., 39, 693-757.
Russel, R.D. and DoW. Allen, 1955, '!'heage of the ear~h
from lead isotope abundances, Monthly NoUces Roy.
Astron. Soc., Geophys. Suppl.,7, 80-101.
Russel. R.D. and R.L. S'tanton, 1959, Anomalous leads and
'the emplacement .of lead sulfide ores, Eeon. Geo1.,
54,' p.SSS.
Russel, R.D. and R.M. Farquhar,
1960, Lead ls01:opes 1n
geology, Intersc1enc:e,Publ1sheJ:8, New YO!:k, N.Y.
Sazh1na, L.I., 1958,'Qn the d1strlbutionof
rUbidiumin
gr~ltes
of the U.S.S.R., Geochem1stry,6,'
602-604'.
Schreiner. G.D.L., 1958, comparison of tile 87Jtb-S7sX' ages
of the red granite of ~e Bu~hveld Complex from
maasureme~t.s on the toi:al xock and separated
mineral fractions,
245, p.11Z.
P~oc •.Roy. Soc. London, Ser.A,
Schumacher, E., 1956, Altersbestimmungen von Ste1nmeteor1ten m1t der RublC11um-StrontiuuiMethode, zeit fur
Naturforsehung, 11a. p.206.
schumacher', B., 1956, Quantitative Besi:lmmungen von
Rubidium 'und Strontium in Steinme~oriten
mit der
massenSp8ctS1X1l8t.rlschen IsotopenveZ'dunnuDgsm9thode,
Helv. Chemica Acta,
39, p.S38.
Shand, S.J., 1947, Eruptive
Inc., Hew York, N.Y.
reeks,
Smales, A.A. and R.R.' Webs~r,
John Wiley and Sons,
1957. 'l"he detemination
of
Z"Ubldium1n sea water by tile s~able isotope dilution
t.ecbnique,
Geoehim. et COsmochlm.Acta,
11, p.139.
-
-275-
Suess, HoEo and H.C. Urey, 1956, Abunaances
ments, Rev. Mod~ Phys •• 28, p.S3.
of the ele-
Suess. HoE. and H.C. Ux-ey,' 19S8~ Die aaufigkeit
der
Elemente in den Plane'ten und ~1et:eor1ten, Handbucb
der Physik, 51, 296-323.
SujkowslQ.. ~.
L.,
1952, Average chemical
the sedimentary
Taylor,
RoB ••
composition
'of
roeks, Am. ~. Se1., 250, 360-374.
1956, i'he Duluth Gabbro Complex, Duluth
Minnesota, Guidebook for ~ield trip No. 1, Minn~apolis meeting of the Geol. Soc. Am.
-
-raylor, S.R., C.H. Bmeleus and C.S. Exley, 1956, Some
anomalous R/Rb &-ai:los 1n igneous
petZ'ologlcal significance,
Acta, 10, 224-229.
rocks
and their
Gsoch1m.' et: Cosmochim.
Turner, P.J. and J. Verhoogen, 1960, Igneous and met:amorph1c pet:rology, 2nd ed., McGraw-Hill Book Company,
Inc.
~E'ekian, K.X., 1955, The abundance of stronUum in
9J~anite and basal~1c rocks, Trans. Am. Geophys.
Union, 36, p.532.
Turek:Lan. 1t.1t. ana J.L. Kulp, 195~, The geochemistry of
strontium, .Geccb~. e~ cosmoc~lm.~cta,10, 245-296.
'1'urekian, K.R.
~e
and KoB. Wedepohl, 1961, Distribution
of
elements in some major uni~s of the earth's
crust, Bull.: Geol. Soc. Am., 72, 175-196.
Urxy,
W.D•• °1936, Ages by 'the helium me1:hods.
II-post-
K~weenawan, Bull. Geo1. Soc. Am., 47, 1211-1233.
V1ncent,E.A., 1960, Analysis by gravimetric and volums~ric methods, flame photometry, colorimetry and
related techn1ques, in Me'thods.1n Geochemistry,
A.A. Smales and L.R. wager ed1~ors,' Intersc1ence
Publishezos.
of distribution
of the chemical elements in tbe earth' s crust,
Vinogradov, A.P., 1956, The regularity
GeOkhim1ya, No.1.
1-52.
-
Wager
l
L.R. and R.L. M1tehell, 1951, The distribution of
trace elemen~s during strong fractiona~ion of basic
magma - a further study of the ,Skaergaard intrusion,
East Greenland,
Gecch1m. e1: Cosmochim. Ac1:a, .1, p.129.
Wager', L.R. and R.L. Mit:chell, 1953, Trace elements in a
suite of Hawaiian lavas, Geocb1m.
Coamocb1m. Ac1:a,
et
3, 217-233.
Webs1:er, R.K.,
J.li.
Morgan and A.A. Smales,
1957, Soma
Recent Harwell analytical work on geochronology,
Trans. Am. Geopbys. Union, 38, 543-545.
'iiclaoan, P.E.,
1948, Isotope
ratios.:
a clue to t;he age
of certain marine sediments, J. Geol•., 56, p.61.
Wickman, If .B., 1954, The "totalamount: of sediments and
the compos:LUon. of the average igneous rock, Geoch1mo
e't C:osmochlm. Acta,S,
p. 97 •
Williams,
A.P., 1932, Genesis of the diamond, 2 vola.,
B. Benn,' London.
Wilson, J.'t., R.D. Russel and R.M. Farquhar, 1956,
Rad1oactivi1:y and age of minerals, Handbuch der
Physik, 47,' p.2Sa.
-277BIOGRAPHY.
The author was born on May 11, 1934, in Tallin,
Estonia.
As a result of the outbreak of the.second
World War the. family was forced to move to ~astez:n
Germany in 1939 and to wes~ern Germany 1n 1945.
.family immigrated ~o Canada1n
London,
The
1952 and settled in
Ontario.
'!'he author c:omple~edhis high schOOl education
at
.the' LOndon Central Collegiate ~n 1953 and 1n 1957
received a B~SC. degree in Geology from the University
of Wesf:ernOntario.
student
He was enxolled
as a graduate
in the Departmen~ of Geology and Geophysics
in
1957.
~ile
at -M.I.T. he. was a balf-time
res~arc:h assis-
tant for two years from 1957 to.1959 and.a part-time
instructor
for Sclen~lfic
German in the fall semesters
"\
~f 1959 and 1960.
in geolog1cal
Foothills
field
'the
aut:hor
has
also
spent six Bummers
wor~ on t.he Canadian
~leld
and ~e
of 'theRoc'ky .Mo~n1:a1n.B•..
As an undergraduate
and as a graduate student at:
M~I.T. 'the author .was awarded -the Board of Goveznors'
~m1ssion
ScholushipII,
the .J.P. Bickell PounClat1on
-278Scholarship,
the Board of Governors'
Scholarsh~p,
.California Standard Company Scholarship.
Gold Medal, the 'Imperial
and a scholarship
the
~he University
Oil Graduate Research scholarship
from the 14.1.'1'. Ca!2adlan T~st
Pund.
The author is a member of the hner1c:an ~ophyslc:al
Union,' the Geochemical
Socie1:y and ~be SOciety of Sigma
Xi.
In september 1959 the author was married to Miss
BarbaraL.L.
Goodell of East Dennis. Massachusetts.