| Abstract | Iron oxide copper-gold (IOCG) deposits host economic quantities of Cu ± Au and may also yield Ag, Co, Bi, Fe, Mo, Ni, PGE, Pb, REE, U, V, Zn and industrial minerals. Iron oxide-apatite (IOA) deposits
are sources of iron ore, and can in some cases contain REE ores. Affiliated deposits include, cobalt-bismuth variants of IOCG deposits rich in critical metals, iron and polymetallic skarn deposits, albitite-hosted uranium and Au-Co-U deposits,
molybdenum-rhenium and iron sulphide-copper-graphite or copper-gold deposits. All these deposit types form within regional-scale iron oxide and alkali-calcic alteration systems. An individual ore system will not encompass this entire array of
deposits, as system evolution and metal endowment depend on tectonics, volcanic activity, depth and geodynamic settings. The large resource potential for base, precious, REE, strategic, critical and nuclear metals, and the clustering of deposits in
districts along extensive geological provinces, make IOCG and affiliated deposits attractive targets for modern exploration. This Special Paper of the Geological Association of Canada documents these ore systems globally, and more specifically their
settings, alteration facies, breccia types and mineral chemistry. Examples discussed include the Olympic Copper-Gold Province and Cloncurry district (Australia), the Great Bear magmatic zone (Canada), the Central Andes (South America), the Bafq
district (Iran), and the Middle-Lower Yangtze River Metallogenic Belt,Kangdian, eastern Tianshan and eastern Junggar districts (China). Complementary information is sourced from the southeast Missouri district (USA), Singhbhum Shear Zone (India),
Norbotten district (Sweden), Bayan Obo deposit (China), and Central Mineral Belt, Kwyjibo district and Romanet Horst (Canada). The diagnostic alteration facies and breccias associated with these ore systems reflect regional chemical and textural
modification of host rocks, resulting from progressive and efficient metasomatic fluid-rock reactions across very steep physicochemical gradients sustained by heat ingress and the ascent and evolution of large hypersaline fluid plumes. Field examples
and processing of large lithochemical and geophysical databases illustrate the footprints of these ore systems and enable the development of new petrological mapping protocols, discriminant diagrams and lithogeochemical tools for
their
characterization. By documenting alteration facies, paragenetic sequences, mineral chemistry, structural controls, and geophysical and geochemical signatures, and framing them into ore genetic models and deposit classes, the examples provide
effective vectors to mineralization and address critical issues in exploring for these deposits worldwide. |
| Summary | (Plain Language Summary, not published)
This scientific paper is a chapter for the Short course Note 21 volume of the Geological Association of Canada untitled Iron oxide copper-gold
(Ag-Bi-Co-U-REE) and affiliated deposits. The paper reviews some of the main outcome of the Targeted Geoscience Initiative 5, project 1. Uranium systems, activity 2.1 Metal pathways and traps in polymetallic (U +/- Fe, Cu, Au, REE) metasomatic ore
systems. The first part provides an overview on the variety of deposit types within these giant ore systems It synthesizes how alteration facies evolve as the systems build-up and how they provide a record of fluid flow paths from sources to
deposits. The paper then addresses the need for synergies to optimize discoveries of IOCG and affiliated deposits, the time it takes between first discoveries and the development of new mining districts, the Australian successes, the social benefits
and finally the prospective districts in Canada. |