Sulfur
91
3) a further depletion in deuterium in the methane being generated
from coal and oil.
Note the similarity in the fractionation trend as discussed for the
carbon isotope composition.
3. Sulfur
At present only a limited number of measurements on 34S/2S ratios
of biological material are available.
MEKHIYEVA and PANKINA (1968) have demonstrated that sulfur of
aquatic plants from a given water is slightly lighter than the sulfur of the
dissolved sulfate. The same results have been obtained by KAPLAN et al.
(1963) for marine organisms - plants and animals.
Several studies have been made on the 34S/2S ratios in natural crude
oil and associated materials, e.g., THODE et al. (1958), HARRISON and THODE (1958), PANKINA and MEKHlYEVA (1964), THODE and
MONSTER (1965), and THODE and MONSTER (1970), THODE and REES
(1970).
.
Sulfur isotope studies of petroleum and related sulfates and sulfides
can give information concerning the possible origin of petroleum sulfur
and concerning the environment in which the petroleum was formed.
Most oils are formed in a marine environment, and it seems reasonable
to assume that ocean water sulfate is the main source of sulfur in petroleum. Since seawater sulfate is rapidly reduced by bacteria in the shallow
muds in contact with the sea, it is very likely that it would be this
reduced sulfur that would finally be incorporated in the petroleum (sulfur originating from the organic primary material is only of minor importance). In general, the £534S-value for petroleum is depleted by "" 15%0
relative to associated evaporite sulfates, which would be in agreement
with a bacterial reduction of ocean water sulfate.
In general, single large oil pools are uniform in isotopic composition.
In contrast, oil pools in reservoir rocks of different geologic ages show a
wide range of isotope ratios W 4 S varies by about 45%0).
The pattern of sulfur isotopes in marine oils is very different from
that in nonmarine oils. For marine oils the £534S-values are related to
those of the contemporaneous oceans. Nonmarine oils have no relation
to the isotope ratios for contemperaneous oceans.
These results, together with the fact that hydrogen sulfide gas derived
from many of these oils has similar isotope ratios, (THODE et aI., 1958)
indicate that there is little fractionation of the sulfur isotopes in the
maturation or degassing of oil during which sulfur is lost. Thus, the
sulfur isotope ratio for oil seems to give information about the sulfur
isotope content of the source sulfur at the time of petroleum formation.
91
3) a further depletion in deuterium in the methane being generated
from coal and oil.
Note the similarity in the fractionation trend as discussed for the
carbon isotope composition.
3. Sulfur
At present only a limited number of measurements on 34S/2S ratios
of biological material are available.
MEKHIYEVA and PANKINA (1968) have demonstrated that sulfur of
aquatic plants from a given water is slightly lighter than the sulfur of the
dissolved sulfate. The same results have been obtained by KAPLAN et al.
(1963) for marine organisms - plants and animals.
Several studies have been made on the 34S/2S ratios in natural crude
oil and associated materials, e.g., THODE et al. (1958), HARRISON and THODE (1958), PANKINA and MEKHlYEVA (1964), THODE and
MONSTER (1965), and THODE and MONSTER (1970), THODE and REES
(1970).
.
Sulfur isotope studies of petroleum and related sulfates and sulfides
can give information concerning the possible origin of petroleum sulfur
and concerning the environment in which the petroleum was formed.
Most oils are formed in a marine environment, and it seems reasonable
to assume that ocean water sulfate is the main source of sulfur in petroleum. Since seawater sulfate is rapidly reduced by bacteria in the shallow
muds in contact with the sea, it is very likely that it would be this
reduced sulfur that would finally be incorporated in the petroleum (sulfur originating from the organic primary material is only of minor importance). In general, the £534S-value for petroleum is depleted by "" 15%0
relative to associated evaporite sulfates, which would be in agreement
with a bacterial reduction of ocean water sulfate.
In general, single large oil pools are uniform in isotopic composition.
In contrast, oil pools in reservoir rocks of different geologic ages show a
wide range of isotope ratios W 4 S varies by about 45%0).
The pattern of sulfur isotopes in marine oils is very different from
that in nonmarine oils. For marine oils the £534S-values are related to
those of the contemporaneous oceans. Nonmarine oils have no relation
to the isotope ratios for contemperaneous oceans.
These results, together with the fact that hydrogen sulfide gas derived
from many of these oils has similar isotope ratios, (THODE et aI., 1958)
indicate that there is little fractionation of the sulfur isotopes in the
maturation or degassing of oil during which sulfur is lost. Thus, the
sulfur isotope ratio for oil seems to give information about the sulfur
isotope content of the source sulfur at the time of petroleum formation.