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SULFIDE MINERALS IN SEDIMENTS
Wilkin*, R T. SULFIDE MINERALS IN SEDIMENTS. Gerard V. Middleton (ed.), Encyclopedia of Sediments: Sedimentary Rocks. Kluwer Academic Publishers, Hingham, MA, ( ):701-703, (2003).
The formation processes of metal sulfides in sediments, especially iron sulfides, have been the subjects of intense scientific research because of linkages to the global biogeochemical cycles of iron, sulfur, carbon, and oxygen. Transition metal sulfides (e.g., NiS, CuS, ZnS, CdS, HgS) have exceedingly low solubility products and might be expected to form during early diagenesis. However, with the exception of iron, d-transition metals are typically present in trace amounts in sediments, which often does not allow for any significant accumulation of sulfide minerals other than those of iron. In contaminated sediments or systems with high metal loadings, sulfides of Zn, Cd, and Cu have been reported. Trace metals are frequently found associated with pyrite and include Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Hg, and sometimes Mn. In particular, As, Hg, and Mo have a high affinity for pyrite and are generally enriched in pyrite relative to bulk sediments. This chapter reviews formation mechanisms of pyrite and precursor iron monosulfides.