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TitleOn the use of the geochemical footprints of iron oxide-copper-gold deposit hydrothermal alteration as an exploration tool
AuthorMontreuil, J -F; Corriveau, L; Potter, E G; Grunsky, E
Source34th International Geological Congress, abstracts; 2012 p. 1
Alt SeriesEarth Sciences Sector, Contribution Series 20120253
Meeting34th International Geological Congress; Brisbane; AU; August 5-10, 2012
ProvinceNorthwest Territories
AreaFab Lake
Lat/Long WENS-117.0000 -116.5000 46.2500 46.0000
Subjectseconomic geology; geochemistry; mineral deposits; mineral occurrences; iron oxides; copper; gold; mineralization; alteration; hydrothermal alteration; hydrothermal deposits; exploration; exploration methods; geochemical interpretations; Great Bear Magmatic Zone
ProgramIron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT), GEM: Geo-mapping for Energy and Minerals
AbstractHydrothermal alteration, formed during the build up of iron oxide copper-gold (IOCG) systems is extensive, indiscriminately replaces host rocks at both local and regional scales and can lead to complete and systemic mineralogical, chemical and textural transformation of precursor rocks. Hydrothermal alteration in IOCG systems also displays a systemic development from sodic, to calcic-iron, and high to low temperature potassic-iron and potassic alteration.
An element mobility study of the Fab system in the Great Bear magmatic zone (Canada) highlights the extreme element mobility in IOCG hydrothermal systems, in which normally immobile elements like Ta, Nb, Th, Ti and the REE are strongly and massively remobilized. Geochemical modelling using the compositional data analysis method and principal component analysis demonstrates that the geochemical signatures of the characteristic sodic, sodic-calcic-iron, calcic-iron, calcic-iron-potassium, potassic and potassic-iron alteration developed as a result of this extreme element mobility. These characteristic zones are statistically different and are reproducible irrespective of the nature of the original host.
PCA has led to the elaboration of IOCG alteration indexes and the construction of an IOCG alteration discrimination diagram, which provides a tool to evaluate if a geochemical composition can be related to an IOCG hydrothermal alteration type. On regional geology maps, the alteration indexes portray the maturity IOCG system.