Sulfideforming

Sulfideforming is the geological process by which sulfide minerals precipitate from sulfur-bearing fluids and accumulate as ore minerals within rocks. It is central to many hydrothermal and magmatic ore-forming systems and occurs wherever metal-rich fluids interact with sources of reduced sulfur under suitable temperature, pressure, and redox conditions. Common sulfide minerals include pyrite and pyrrhotite (iron sulfides), chalcopyrite and bornite (copper iron sulfides), and sphalerite and galena (zinc and lead sulfides).

Formation occurs as hydrothermal fluids derived from magmatic or metamorphic sources rise and cool or mix with seawater or meteoric fluids, causing sulfide saturation and precipitation. Redox shifts, pH changes, and pressure drop can drive sulfide deposition, while sulfide liquids may fractionate metals during crystallization, concentrating nickel, copper, zinc, and other chalcophile elements. Textures range from disseminated networks to massive sulfide bodies and veinlets, often with associated alteration halos.

Major sulfide-forming deposit types include magmatic sulfide deposits in ultramafic to mafic rocks (nickel and copper mineralization), volcanic-hosted massive sulfide (VHMS) deposits at submarine vents, and sedimentary-exhalative (SEDEX) deposits formed near ancient seafloors. Porphyry copper systems and related deposits may also host significant sulfide mineralization. Studying sulfideforming processes aids understanding of crustal differentiation, ore genesis, and the global cycling of chalcophile elements.