Garnets in the Yinachang Fe-Cu deposit, Kangdian region, China: Mineralogical and geochemical insights into fluid-rock dominated iron oxide-copper–gold (IOCG) mineralization

Garnet is an important metasomatic mineral in iron oxide-copper–gold (IOCG) ore systems, but its crystallization mechanisms and relationship to fluid evolution in IOCG are poorly understood. The Yinachang deposit is a typical IOCG deposit in the Kangdian region, southwest China. Zoning of the deposit include a breccia zone, a K-Fe alteration zone which can be subdivided into proximal and intermediate zones, and distal Na alteration zone. Iron ore bodies occur both in the breccias and in the meta-clastic rocks of the Yinmin Formation, and are replaced or cut by later Cu-Au-bearing layers and veins. The sequence of events include pre-ore Na±Fe alteration (stage 1), K-Fe±REE mineralization (stage 2), Cu±Au mineralization (stage 3), and barren veins (stage 4).