Meteorites
49
Table 8. Distribution and isotopic composition of sulfur in the Orgueil carbonaceous chondrite. (After MONSTER et al., 1965)
Form of sulfur
Percent of sulfur
b 34 S
by weight
MgS04 x 7 H20
2.1
-1.3
Elemental sulfur
1.8
1.5
Troilite sulfur
0.8
2.6
Other forms of sulfur
0.3
Total sample
5.0
0.4
In contrast to most terrestrial environments, sulfate in the Orgueil
meteorite is the isotopically lightest sulfur compound. MONSTER et al.
(1965) suggested that kinetic isotope effects in a sulfur-water reaction
may be responsible for the genesis of sulfur compounds in meteorites.
There is no evidence for biological activity having occurred in meteorites, since in this case the sulfate should have been enriched in the heavy
isotope.
HULSTON and THODE (1965) and KAPLAN and HULSTON (1966) have
measured the 33Sj3 2 S and 36Sj32S ratios in meteoritic material. Their data
give strong evidence against variations due to inhomogeneities in the
processes of nucleosynthesis and due to cosmic ray effects.
Carbon isotope studies on meteorites have been carried out by
CRAIG (1953), BOATO (1954), CLAYTON (1963 b), VINOGRADOV et al.
(1967), BELSKY and KAPLAN (1970), KROUSE and MODZELESKI (1970), and
SMITH and KAPLAN (1970).
BOATO (1954) determined the isotopic composition of total carbon in
carbonaceous chondrites. His results are summarized in Fig. 20. BOATO
argued that whatever the actual processes were that finally produced the
various types of chondrites, the decrease in l3C-content with decreasing
water and carbon content (shown in Fig. 20) may reflect an isotopic effect
during the particular process by which the volatiles were lost.
Besides the bulk carbon isotopic composition, the various carbon
phases occurring in meteorites (graphite, diamond, carbides, "organic"
matter, carbonates) have been separately investigated. According to VINOGRADOV et al. (1967), the J 13 C-values of the "organic" material vary
from - 22.0 to - 28.7%0, whereas the graphites range from - 5.0 to
- 6.3%0. CRAIG (1953) examined the l3C;nC ratio in cohenite from the
Canyon Diablo iron meteorite and found a J-value of -17.9%0, quite
different from the l3C/12C ratio for the graphite ( - 6.3%0) from the same
meteorite.
Carbonates which rarely occur in carbonaceous chondrites, have
been analyzed by CLAYTON (1963b) and KROUSE and MODZELESKI
49
Table 8. Distribution and isotopic composition of sulfur in the Orgueil carbonaceous chondrite. (After MONSTER et al., 1965)
Form of sulfur
Percent of sulfur
b 34 S
by weight
MgS04 x 7 H20
2.1
-1.3
Elemental sulfur
1.8
1.5
Troilite sulfur
0.8
2.6
Other forms of sulfur
0.3
Total sample
5.0
0.4
In contrast to most terrestrial environments, sulfate in the Orgueil
meteorite is the isotopically lightest sulfur compound. MONSTER et al.
(1965) suggested that kinetic isotope effects in a sulfur-water reaction
may be responsible for the genesis of sulfur compounds in meteorites.
There is no evidence for biological activity having occurred in meteorites, since in this case the sulfate should have been enriched in the heavy
isotope.
HULSTON and THODE (1965) and KAPLAN and HULSTON (1966) have
measured the 33Sj3 2 S and 36Sj32S ratios in meteoritic material. Their data
give strong evidence against variations due to inhomogeneities in the
processes of nucleosynthesis and due to cosmic ray effects.
Carbon isotope studies on meteorites have been carried out by
CRAIG (1953), BOATO (1954), CLAYTON (1963 b), VINOGRADOV et al.
(1967), BELSKY and KAPLAN (1970), KROUSE and MODZELESKI (1970), and
SMITH and KAPLAN (1970).
BOATO (1954) determined the isotopic composition of total carbon in
carbonaceous chondrites. His results are summarized in Fig. 20. BOATO
argued that whatever the actual processes were that finally produced the
various types of chondrites, the decrease in l3C-content with decreasing
water and carbon content (shown in Fig. 20) may reflect an isotopic effect
during the particular process by which the volatiles were lost.
Besides the bulk carbon isotopic composition, the various carbon
phases occurring in meteorites (graphite, diamond, carbides, "organic"
matter, carbonates) have been separately investigated. According to VINOGRADOV et al. (1967), the J 13 C-values of the "organic" material vary
from - 22.0 to - 28.7%0, whereas the graphites range from - 5.0 to
- 6.3%0. CRAIG (1953) examined the l3C;nC ratio in cohenite from the
Canyon Diablo iron meteorite and found a J-value of -17.9%0, quite
different from the l3C/12C ratio for the graphite ( - 6.3%0) from the same
meteorite.
Carbonates which rarely occur in carbonaceous chondrites, have
been analyzed by CLAYTON (1963b) and KROUSE and MODZELESKI