2019 年 69 巻 2 号 p. 97-109
Recent progresses on the iron oxide-copper-gold (IOCG) deposits, especially on principal Chilean deposits, are summarized to clarify metallogenesis and exploration of the type of deposits in Mesozoic extensional subduction regime. The principal composite-mode deposits (Candelaria, Punta del Cobre, Mantoverde) are closely associated with Cretaceous Atacama fault system, and are characterized by the typical Na-Ca-K alteration with the early-stage magnetite (or hematite) and the following Mg alteration with copper-sulfide and gold mineralizations. Fluid inclusion and stable isotope studies suggest that the IOCG deposits were formed by high-temperature hypersaline magmatic-hydrothermal fluids. If the IOCG deposits are generated from FeCl2-bearing magmatic fluids, the spatial-temporal relation between the IOCG and iron oxide-apatite (IOA) deposits is well explained by the magmatic magnetite-bubble segregation model (Knipping et al., 2015b; Simon et al., 2018). Nevertheless, a few problems still remain unsolved in the genetic model including contribution of basinal brines.
