54
C. Variations of Stable Isotope Ratios in Nature
rived in large part from ISO-rich sialic crust by partial melting or assimilation and/or their differentiation occurred at much lower temperatures.
SHIEH and SCHWARCZ (1971) found that there are two different groups of
granites in the Grenville Province of Canada: 1) higher-level intrusions
into greenschist to middle amphibolite metamorphic terranes, with c5 18 0
ranging from 8.2 to 14%0, and 2) granite gneisses gradational into migmatite and upper amphibolite facies paragneiss, with c5 18 0-values between 6.5 and 8.8%0.
MATSUHISA et al. (1972) found a similar grouping: The granites intruded into a non-metamorphic zone showed "normal" 180rO ratios
between 8 and 9%0, whilst those intruded into a regional metamorphic
zone are enriched in 18 0 (c5 18 0: 10 to 13%0). MATSUHISA et al. (1972)
attributed this enrichment to isotopic exchange between the granitic
magma and the surrounding metamorphic rocks during regional metamorphism. These examples demonstrate that a simple relationship
among granites produced by differentiation of basic complexes with low
c5 18 0-values and granites produced by partial melting of metasedimentary rocks with high c5-values, unfortunately does not exist.
12
11
10
9
~ 8
Q;
§,7
o
E
I 6
!:!
~
:::J 5
o
./Garnet schists
.1
I
•
o I
a
Q:] Kyanite and
'I sillimanite schists
I
o
j 0 Plutonic
I
granitic rocks
I
II. Horse Mesa rhyolite
Lassen
I
dacite. I
I
I
I
I
I
!
/ ~ t.Qtz-biot =0.59
I
t.Qtz-mag
1
I
I
°O~~--~2--~3--~4--~5--~6~~7~~8~~9
l:!. Quartz - biotite
Fig.22. Relationship between LI-values of quartz-magnetite and quartz-biotite for
quartz-biotite-magnetite assemblages from igneous and metamorphic rocks. Data
are from TAYLOR and EpSTEIN (l962a), GARLICK and EpSTEIN (1967), and TAYLOR
(1968a). (From TAYLOR, 1968 a)
C. Variations of Stable Isotope Ratios in Nature
rived in large part from ISO-rich sialic crust by partial melting or assimilation and/or their differentiation occurred at much lower temperatures.
SHIEH and SCHWARCZ (1971) found that there are two different groups of
granites in the Grenville Province of Canada: 1) higher-level intrusions
into greenschist to middle amphibolite metamorphic terranes, with c5 18 0
ranging from 8.2 to 14%0, and 2) granite gneisses gradational into migmatite and upper amphibolite facies paragneiss, with c5 18 0-values between 6.5 and 8.8%0.
MATSUHISA et al. (1972) found a similar grouping: The granites intruded into a non-metamorphic zone showed "normal" 180rO ratios
between 8 and 9%0, whilst those intruded into a regional metamorphic
zone are enriched in 18 0 (c5 18 0: 10 to 13%0). MATSUHISA et al. (1972)
attributed this enrichment to isotopic exchange between the granitic
magma and the surrounding metamorphic rocks during regional metamorphism. These examples demonstrate that a simple relationship
among granites produced by differentiation of basic complexes with low
c5 18 0-values and granites produced by partial melting of metasedimentary rocks with high c5-values, unfortunately does not exist.
12
11
10
9
~ 8
Q;
§,7
o
E
I 6
!:!
~
:::J 5
o
./Garnet schists
.1
I
•
o I
a
Q:] Kyanite and
'I sillimanite schists
I
o
j 0 Plutonic
I
granitic rocks
I
II. Horse Mesa rhyolite
Lassen
I
dacite. I
I
I
I
I
I
!
/ ~ t.Qtz-biot =0.59
I
t.Qtz-mag
1
I
I
°O~~--~2--~3--~4--~5--~6~~7~~8~~9
l:!. Quartz - biotite
Fig.22. Relationship between LI-values of quartz-magnetite and quartz-biotite for
quartz-biotite-magnetite assemblages from igneous and metamorphic rocks. Data
are from TAYLOR and EpSTEIN (l962a), GARLICK and EpSTEIN (1967), and TAYLOR
(1968a). (From TAYLOR, 1968 a)