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TitleMapping mineral systems with IOCG and affiliated deposits: a facies approach
AuthorCorriveau, L CORCID logo; Montreuil, J F; De Toni, A F; Potter, E GORCID logo; Percival, J BORCID logo
SourceMineral systems with iron oxide copper-gold (IOCG) and affiliated deposits; Geological Association of Canada, Special Paper 52, 2022 p. 69-111
Alt SeriesNatural Resources Canada, Contribution Series 20200398
PublisherGeological Association of Canada
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
Lat/Long WENS-119.1667 -116.0000 66.3333 63.3333
Subjectseconomic geology; metallic minerals; mineralogy; Science and Technology; Nature and Environment; iron oxides; gold; copper; mineral deposits; facies
Illustrationsphotomicrographs; tables; photographs; diagrams; location maps
ProgramTargeted Geoscience Initiative (TGI-5) Uranium ore systems
Released2022 07 01
AbstractOre systems with regional-scale iron oxide and alkali-calcic metasomatism host iron oxide copper-gold, iron oxideapatite, iron and polymetallic skarn, albitite-hosted uranium, and epithermal deposits. The deposits develop through prograde, retrograde, telescoped and cyclical metasomatic paths across diverse rocks types, leading to alteration zones with highly variable mineral assemblages, mineral contents, textures, structures and spatial distribution. Deciphering the evolution of these mineral systems through mapping alteration assemblages, veins and breccia is key to effective exploration, but can be hampered by the complexities of the systems and resemblance of some metasomatites to common sedimentary, volcanic, plutonic or metamorphic rocks. In the Great Bear magmatic zone in northern Canada, a series of well exposed and preserved mineralized systems were mapped from their sub-volcanic roots to their shallowest levels as well as along fault zones. The great complexity of the metasomatic rocks observed and described in this paper was resolved by applying a metamorphic petrology 'facies' approach to alteration mapping. This approach defines a given facies according to the spectrum of mineral assemblages that crystallized under similar physicochemical conditions and produced diagnostic bulk compositions. Rather than simply reflecting element enrichment or depletion, each alteration facies is a product of systematic elemental partitioning between fluid and rock, and the stability of the resultant mineral assemblages as the magmatic-hydrothermal systems evolve. This approach greatly simplifies the descriptive terminology and alteration mapping protocols for iron oxide and alkalicalcic alteration systems and their deposits.
Summary(Plain Language Summary, not published)
This scientific paper is a chapter of the Geological Association of Canada Special Paper 52 entitled 'Iron oxide copper-gold (Ag-Bi-Co-U-REE) and affiliated deposits'. It presents a protocol and the needed terminology for mapping alteration facies in polymetallic metasomatic ore systems associated with iron oxide copper-gold (IOCG) and affiliated iron, uranium or critical metal deposits. The paper also addresses the rationale for using an alteration facies approach to mapping and describes the field methods and the attributes of the alteration zones, veins and breccia that form these systems. Moreover, it refines the definition of their prograde and retrograde metasomatic paths to best portray their depth to surface evolution and the varied stages of retrogression observed. The research is an outcome of the Targeted Geoscience Initiative Uranium systems project and of an earlier project (IOCG/Great Bear project) of the Geomapping for Energy and Minerals program.

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