'Massive sulfide deposits, consisting of pyrite and/or pyrrhotite and various ratios of chalcopyrite, sphalerite, and galena, are commonly associated with volcanic rocks that accumulated in eugeosynclines.' They are related genetically to these volcanic rocks rather than to granitic rocks. The source of the base metals may have been primary volcanogenic concentrations, dispersed metals in volcanics, or later magmas. Hydrothermal (meaning simply 'hot-water') solutions of various temperatures, probably containing alkali chlorides, have commonly been the transporting agent. The trace-element content of sulfides (Se and V in pyrite) and isotope studies are promising directions for research on genesis.

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