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TitleGeochemical composition of chromite from Alexo komatiite in the western Abitibi greenstone belt: Implications for mineral exploration
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LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorPagé, P; Barnes, S-J; Méric, J; Houlé, M G
SourceTargeted Geoscience Initiative 4: Canadian nickel-copper-platinum group elements-chromium ore systems -- fertility, pathfinders, new and revised models; by Ames, D EORCID logo (ed.); Houlé, M G (ed.); Geological Survey of Canada, Open File 7856, 2015 p. 187-195, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Targeted Geoscience Initiative 4: Canadian nickel-copper-platinum group elements-chromium ore systems -- fertility, pathfinders, new and revised models
File formatpdf
AreaPorquis Junction
Lat/Long WENS -81.0000 -80.7333 48.7500 48.5833
Subjectsgeochemistry; igneous and metamorphic petrology; chromite; mineral exploration; whole rock geochemistry; basalts; volcanic rocks; komatiites; chromium geochemistry; osmium; iridium; ruthenium; rhodium; Abitibi Greenstone Belt; Superior Province; Alexo komatiite
ProgramTargeted Geoscience Initiative (TGI-4) Mafic-Ultramafic Ore Systems
Released2015 06 22
AbstractThis study, which focuses on the composition of chromite from mineralized and unmineralized komatiitic flows and sills from the Alexo Mine area in Dundonald Township, within the western Abitibi greenstone belt, aims to develop new exploration tools for poorly exposed mineralized komatiitic systems. It is possible to clearly identify chromite derived from massive sulphide (having very high Cr# and depleted Ru content) from chromite derived from barren and poorly mineralized samples based on its composition. LA-ICPMS analyses show that chromite from massive sulphide are depleted in Al, Ni, and Mg, and are enriched in Ti, Zn, Mn, Fe and V compared to chromite from barren samples; however, alteration can also modify chromite chemistry. Samples from the Hart deposit are pervasively altered and their chromite compositions are enriched in Fe, Zn, Co, and Mn, and are depleted in Mg. We propose a binary diagram of Ni/Mn versus Ni/Cr ratios which can be used to clearly discriminate between sulphide segregation prior to chromite crystallization and later superimposed alteration. Mass balance calculations show that chromite does fractionate and concentrate Ir-group platinum-group elements (IPGE: Os, Ir, Ru) and Rh but that chromite contribution to the whole-rock IPGE and Rh budget is rather limited, and for mineralized samples, this contribution is even smaller. From these results, it is clear that IPGE+Rh-rich phases (nano- to micro- platinum-group minerals) are needed to account for the IPGE and Rh contents in whole-rock geochemistry.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This volume summarizes 22 research activities completed under the TGI-4 Ni-Cu-PGE-Cr ore systems project that focused on revised and new geologic models for Ni-Cu-PGE, PGE-Cu and Cr deposits, innovative techniques for determining potential fertility of intrusion (Ni-Cu-PGE), and defining pathfinders for Ni-Cu-PGE mineralization.

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