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TitleGeochemical signatures of metasomatic ore systems hosting IOCG, IOA, albitite-hosted uranium and affiliated deposits: a tool for process studies and mineral exploration
AuthorBlein, O; Corriveau, LORCID logo; Montreuil, J F; Ehrig, K; Farbis, A; Reid, A; Pal, D C
SourceMineral systems with iron oxide copper-gold (IOCG) and affiliated deposits; Geological Association of Canada, Special Paper no. 52, 2022 p. 1-40
Alt SeriesNatural Resources Canada, Contribution Series 20200491
PublisherGeological Association of Canada
Mediapaper; on-line; digital
File formatpdf
Lat/Long WENS-180.0000 180.0000 90.0000 -90.0000
Subjectsgeochemistry; Science and Technology; Nature and Environment; metallic minerals; copper; gold; mineral deposits; iron oxides; hydrothermal deposits
Illustrationslocation maps; graphs; diagrams; cross-plots
ProgramTargeted Geoscience Initiative (TGI-5) Uranium ore systems
Released2022 07 01
AbstractIron oxide copper-gold (IOCG) deposits comprise a wide range of hydrothermal alteration types that intensively replace their host rocks. These deposits and affiliated deposits, notably iron oxide-apatite (IOA), IOCG, skarn, albitite-hosted uranium or Au-Co-U, and polymetallic vein deposits form through prograde, retrograde, tectonically telescoped, and cyclical metasomatic paths within regional-scale iron oxide and alkali-calcic alteration (IOAA) ore systems. From the roots of the systems at the base of the upper crust to the epithermal caps, these alteration types form distinct alteration facies that prograde from: 1) Na (albitite) and local skarn to 2) high-temperature Ca-Fe, 3) high-temperature K-Fe, 4) transitional K (brecciated felsite) and K-Ca-Mg (potassic skarn), 5) low-temperature hydrolytic K-Fe and Ca-Fe-Mg and 6) epithermal alteration. Each alteration facies has distinct chemical compositions from which to assess the maturity of systems and their potential fertility. The best geochemical discriminants for each alteration facies are their Na-Ca-Fe-K-Mg molar proportions. In parallel, aluminum + silica proportions instead of magnesium best discriminates IOAA systems from those hosting epithermal, porphyry, volcanogenic massive sulphide and sedimentary-exhalative deposits. Reporting cationic bar plots on the IOCG discriminant diagram yields a first-order identification of metasomatic processes that affect whole-rock composition and ore deposition. In this contribution, we investigate the footprints of key metasomatic systems from Laurentia in Canada, the Gawler Craton in Australia and other global examples. We utilise an extensive database of geochemical analyses from Olympic Dam, Acropolis, Punt Hill and other systems of the Olympic Copper-Gold Province as well as from the Great Bear magmatic zone, Romanet Horst, Central Mineral Belt, and Singhbhum Shear Zone. The footprints of these systems provide novel tools to discriminate least-altered rocks from metasomatites, assess alteration intensity and probable protoliths, follow the incremental alteration of a host at a specific alteration facies, characterize the sequential depth-to-surface development of highly intense alteration and identify tectonically telescoped metasomatic paths. Metal contents significantly vary according to alteration facies and record metal pathways from sources to deposits. The results provide innovative exploration vectors for IOCG and affiliated deposits and more global means to assess the mineral potential of prospective settings. In addition, distinct signatures emerge from one system to the other enhancing modelling capabilities and detection of mineral systems through processing of large corporate databases.
Summary(Plain Language Summary, not published)
Iron oxide copper-gold (IOCG) and affiliated deposits globally host significant resources in copper, gold, iron, cobalt, uranium, rare-earths and other critical, base and precious metals but remain significantly under-explored in Canada. This paper documents the geochemical evolution of representative Canadian mineralized systems (Great Bear magmatic zone, Central Mineral Belt and Romanet Horst) and compares them with global examples such as the Olympic Dam deposit (Australia). The system geochemical footprints record the metal pathways from sources to deposits and serve as mappable criteria for mineral potential assessment of prospective settings. Distinct signatures emerge from one system to the other enhancing geochemical modelling capabilities and detection of mineral systems through processing of large corporate databases. The regional footprints are unveiled through collaborations between government surveys, private sector and academia from France, Canada, Australia and India.

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