Iron oxide copper-gold (IOCG) deposits – A review (part 1): Settings, mineralogy, ore geochemistry and classification

Abstract

Characteristics of ten of the world's metallogenic provinces hosting iron oxide Cu-Au (IOCG) deposits have been critically assessed, including geochronology, geological and tectonothermal evolution, alteration-mineralisation parageneses, and ore geochemistry. A new classification framework is proposed in which IOCG deposits form the major part of a global family of Cu-Au-Fe (± Co, REE) or CGI deposits that also includes Fe-rich Cu-Au deposits lacking significant iron oxides. The CGI family is subdivided on the basis of combined tectonic setting, ore geochemistry, and oxidation state of ore-related mineralogy. Three subtypes of CGI deposits have elevated REE ± U, F and Ba and/or enrichments in Co (± Ni, Bi, Se, Te), with known deposits occurring in Precambrian syn-and post-orogenic settings. A fourth subtype of CGI deposits generally lacks significant enrichments in REE, U, F, Ba, Co, Ni, Bi, Se and Te and occur mainly in Phanerozoic Andean type magmatic arc settings. The REE-and/or Co-rich CGI deposit subtypes are geologically and geochemically distinct from porphyry Cu (-Au), skarn Fe-Cu and iron oxideapatite (IOA) deposits, although there are some shared features. The low-REE-U-Co arc-hosted