ABSTRACT
Sulfur is the 14th most abundant element in the Earth’s crust and can exist in redox states from −2 to +6 (Table 20.1). Inorganic sulfur occurs most commonly in the −2, −1, 0, and +6 oxidation states, represented by suldes (e.g., HS−/ H2S and pyrite, FeS2), elemental sulfur (S0), and sulfate (SO42−), respectively (Roy and Trudinger, 1970). The dominant forms of sulfur in the geologic record are base-metal sulde minerals (i.e., particularly pyrite) and sulfates, preserved both in sulfate evaporite minerals (gypsum and anhydrite) (Holser, 1997) and as carbonate-associated sulfate, where sulfate substitutes into the carbonate mineral lattice at ~100 to 1000 ppm levels (Burdett et al., 1989).
