Mechanisms of pyrite and marcasite formation from solutions between 25 and 300 degrees Celsius.

摘要

The iron disulfides, pyrite and marcasite, only form from solutions supersaturated with respect to both iron monosulfides (amorphous FeS, mackinawite, greigite, and pyrrhotite) and the iron disulfides, via the formation and subsequent conversion of an iron monosulfide precursor. Nucleation of iron disulfides from solutions undersaturated with respect to iron monosulfides, but supersaturated with respect to pyrite and marcasite, is inhibited. Growth of pyrite and marcasite is, however, possible under those conditions. The reaction between ferrous ions and polysulfide species, which is commonly inferred to lead to FeS;The conversion of iron monosulfide precursor to FeS;Below 100;Above 100;The rate of the conversion depends mainly on sulfur source. Sulfidation with zerovalent sulfur (polysulfides or elemental sulfur) as a reactant is the fastest process to form pyrite or marcasite at any temperature. Sulfidation with hydrogen sulfide or bisulfide as a reactant proceeds only about 200;The inhibition of FeS