δ34S = ((34S/32S sample/34S/32S standard) -1) x 1000
Standard is troilite (FeS) from Canyon Diablo meteorite in Arizona.
S=22.22 It is cosmically primitive and unaffected by organic processes on the
What are the proportions of S isotopes?
S = 95.02%
S = 0.75%
1. Fractionation of isotopes between sulfide and sulfate minerals in ores varies with
the temperature of deposition.
2. The initial isotope ratio is related to the source of sulfur: mantle, crust, or
3. The relative amounts of oxidized and reduced S species in solution are
proportional to T, pH, and fO2.
4. For marine sulfate, (precipitation from sea water), the range in 34S‰ is from +10
to + 30.
5. For organic processes, in the consumption of SO4-2 to make H2S, it is easier to
break 32S-O bonds. Thus lighter SO4-2 is consumed and lighterH2S emitted.
Sedimentary sulfides are light and have negative δ34S, for example in the Red Sea
they are about -25 to -35 ‰.
6. For inorganic sulfur, the proportion of S is enriched in more oxidized ions such
7. For inorganic sulfur, the heavier isotopes are most abundant in pyrite with
amounts decreasing progressively in sphalerite, chalcopyrite and galena. These
are related to the temperature of formation, and can be used as a geothermometer.
Providencia, Mexico—Pb-Zn thermal springs
Pasto Bueno, Peru—Cu porphyry and veins
Darwin Calif—Pb-Zn veins
Black Hills—Au shear zone hosted
Kuroko—VMS deposits in Japan
Pine Point—Mississippi Valley Type Pb-Zn
Park City—Pg-Ag replacement deposits (skarns)