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TitleCompositional data analysis of hydrothermal alternations in IOCG systems, Great Bear magmatic zone, Canada: to each alteration types its own geochemical signature
AuthorMontreuil, J -F; Corriveau, L; Grunsky, E C
SourceGeochemistry: Exploration, Environment, Analysis vol. 13, no. 4, 2013 p. 229-247,
Alt SeriesEarth Sciences Sector, Contribution Series 20110237
PublisherGeological Society of London
Mediapaper; digital; on-line
File formatpdf
ProvinceNorthwest Territories
NTS86E; 85N; 86C; 86D; 86E; 86F; 86K
AreaHottah Lake; Faber Lake
Lat/Long WENS-119.0000 -116.0000 66.5000 63.5000
Subjectsgeochemistry; metallic minerals; mineralization; iron oxides; copper; gold; alteration; hydrothermal alteration; geochemical analyses; geochemical interpretations; Great Bear magmatic zone
Illustrationsgeochemical analyses; geochemical plots; location maps
ProgramGEM: Geo-mapping for Energy and Minerals, Iron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT)
Released2013 09 27
AbstractIron oxide copper-gold (IOCG) systems are characterized by a wide range of hydrothermal alteration types that indiscriminately and intensively replace their host rocks over areas of >100 km2. At the scale of a system, element mobility and chemical changes associated with alteration are of a magnitude beyond that of any other types of hydrothermal systems and also affect normally immobile elements. Least to non altered precursor rocks can be hard to find and in some cases the nature of the precursor rock itself remains uncertain as both original composition and textures have been severely modified. These properties of IOCG hydrothermal alteration zones limit the applications of mass-balance systems analysis (e.g. Gresen's equations) for their lithogeochemical characterization. In contrast, principal component analysis (PCA) of whole-rock geochemical data from a large suite (386 samples) of hydrothermally altered rocks has enabled the characterisation of the main signatures of the diagnostic alteration types as well as providing insights on coupling and decoupling of elements as alteration evolves. Samples were selected from the Port Radium-Echo Bay and NICO-Sue Dianne IOCG districts and some IOCG systems of the central Great Bear magmatic zone (Fab and DeVries Lake) from the Northwest Territories in Canada. Results show that K-rich alteration is characterized by strong enrichments in K, Al, Ba, Si, Rb, Zr, Ta, Nb, Th and to a lesser extent U. In contrast, calcic-iron alteration leads to strong enrichments in Ca, Fe, Mn, Mg, Zn Ni and Co. These variations in composition can be portrayed by a series of IOCG alteration index and discriminant diagrams. Combined with an IOCG alteration sequencing model, documentation of the lithogeochemical footprint of IOCG systems provides a useful tool to identify areas favourable for IOCG mineralization, assess the potential fertility and maturity of their host hydrothermal system and ultimately vector to ore during exploration.