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TitleSignatures paragénétiques et lithogéochimiques des systèmes métasomatiques polymétalliques à oxydes de fer et à éléments alcalins et calciques : des outils d'exploration et d'interprétation
AuthorCorriveau, LORCID logo; Blein, O; Reid, A; Trapy, P -H; Gervais, F; Cayer, A; Pelletier, J; Pelletier, M
SourceQuébec Mines : résumés des conférences et des photoprésentations; Quebec Department of Energy and Natural Resources, Various Documents DV 2017-03, 2017 p. 67 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20170306
PublisherGouvernement du Québec
MeetingQuébec Mines 2017; Québec, QC; CA; November 20-23, 2017
Mediaon-line; digital
File formatpdf
Subjectseconomic geology; igneous and metamorphic petrology; geochemistry; Science and Technology; Nature and Environment; mineral deposits; metasomatic deposits; polymetallic ores; skarn deposits; uranium; iron oxides; gold; copper; mineral exploration; exploration methods; paragenesis; lithogeochemistry; mineral associations; tectonic setting
ProgramTargeted Geoscience Initiative (TGI-5) Uranium systems
Released2017 11 01; 2018 01 01
The spatio-temporal, chemical and genetic links between albitite-hosted U and Au-Co-U deposits, iron oxide Cu-Au or rare earth deposits (IOA and IOCG) and polymetallic skarns in mineral systems of the Grenville and Bear provinces in Canada and the Olympic Cu-Au Province in Australia illustrate that alteration facies control metal precipitation and associations in these systems not metal or fluid sources. The diagnostic composition of each facies helps prognosticate potential deposit types and discriminate these ore systems from other ore systems even after their metamorphism at high grade. The most fertile systems are those where albitites and high temperature Ca-Fe and K-Fe alteration facies have evolved to low temperature K-Fe and Ca-Mg facies. Reactivation of systems, including metamorphosed ones, results in remobilisation of metals along breccias and veins. Challenges to mineral exploration posed by metamorphism and remobilisations can be overcome through alteration mapping and chemical discriminations as illustrated by our Grenvillian case study at granulite facies. The Bondy gneiss complex in the Central Metasedimentary Belt shows strong lithologic and geochemical affinities with hematite-group IOCG deposits (e.g., Olympic Dam and Mantoverde) and their epithermal roof (e.g., Great Bear), which supports petrological modeling where reactions between iron oxides and phyllosilicates give rise to metamorphic assemblages rich in garnet, pyroxene or biotite as observed in the complex. The Cu(-Ag) veins represent late remobilisations from the host alteration facies. Alkaline rocks (1.07 Ga) cut the metasomatic system, its volcano-plutonic host (1.36-1.39 Ga) and their gneissic fabric. Another system has similar features north of the Belt, the Mitchi property, where a series of Cu-Ag-Mo, Cu-Au-Ag-Co-Ni-W, REE-U-Th-Mo showings are associated with phlogopite-bearing skarns and magnetite-bearing gneisses and breccias. The holistic nature of the alteration facies model for iron oxide alkali-calcic alteration systems and the examples of spatio-temporal relationships between deposit types illustrate the advantages of a broader exploration target for under-explored but IOCG prospective terranes of Canada and Australia, including those metamorphosed to high grade.
Summary(Plain Language Summary, not published)
The uranium system project of the Targeted Geoscience Initiative Program examines the processes involved in the genesis of deposits within iron oxide and alkali-calcic alteration systems in order to develop effective exploration tools for known districts and their possible extensions into under-explored terranes. A regular space-time, chemical and genetic evolution links albitite-hosted U and Au-Co-U deposits to IOCG, iron oxide-rare earth and some skarn deposits. Alteration facies predominantly controls precipitation of metals and metalliferous associations, not metal or fluid sources. The diagnostic compositions of the facies make it possible to estimate the potential fertility of the studied systems and to distinguish them from other families of deposits even if metamorphosed to high grade. The recommended genetic model explains the alteration facies and the type of mineralisation observed within systems hosting deposits. It is also applicable to the studied Canadian settings, which, although promising, remain poor in deposits of this type as still heavily under-explored.

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