Geochemistry of Magmatic Ore Deposits
The generation of ores from igneous rocks depends on the operation of common igneous processes in uncommon ways. Deposits of incompatible lithophile elements form when magmas containing unusually high concentrations of these rare elements fail to freeze at eutectic points, permitting their enrichment by extreme degrees of fractional crystallization. Deposits of compatible elements, such as Cr, Ti, and V, form when high-degree mantle melts undergo unusually effective processes of mixing or phase separation, including crystal settling or liquid immiscibility. Chalcophile element deposits form because of the extremely efficient segregration of very small quantities of immiscible sulfide liquid from large volumes of fertile mafic magmas that themselves were formed in the complete absence of sulfide melt in their mantle sources.