IOCG

IOCG stands for iron oxide copper gold deposits, a widely used classification for a family of hydrothermal ore deposits that are dominated by iron oxide minerals with copper and gold mineralization. The term reflects the common association of copper-bearing ore with magnetite or hematite-rich rocks.

Geology and mineralogy are central to IOCG deposits. The ore bodies typically contain iron oxides (magnetite or hematite) alongside copper minerals such as chalcopyrite and bornite, and often host gold and silver as accessory metals. Sulfide content can vary from sparse to substantial, and alteration halos around the ore body frequently include potassic and hematite- or silica-rich styles. IOCG systems are usually large and can show extensive alteration zones that extend into surrounding rocks.

Formation and setting are impacts of long-lived magmatic-hydrothermal activity. IOCG deposits are commonly linked to significant intrusions and crustal-scale fluid circulation, often in extensional or post-collisional tectonic settings. They may form in diverse lithologies but share the geochemical signature of iron oxide mineralogy with copper-gold mineralization, sometimes over very large footprints.

Economic and mining context. IOCG deposits are typically high-tonnage and can range from low to moderate copper grades with appreciable gold credits. They are commonly mined by open pit methods when feasible, with processing designed to recover copper and gold from oxide and sulfide mineralogy. Ore processing often emphasizes oxide copper recovery and subsequent sulfide flotation where applicable.

Distribution and examples. IOCG deposits are found in several regions worldwide, with Australia hosting several of the largest and most studied systems. Olympic Dam in South Australia is the largest example. Other Australian IOCG deposits include Prominent Hill and Carrapateena. The IOCG concept is used to describe a broad, evolving class of copper-gold-iron ore systems recognized for their distinctive mineralogy and alteration.