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TitleGenesis of chromite deposits by dynamic upgrading of Fe ± Ti oxide xenocrysts
AuthorLesher, C M; Carson, H J E; Houlé, M G
SourceGeology vol. 47, no. 3, 2019 p. 207-210, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20190118
PublisherGeological Society of America
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
Lat/Long WENS -86.2278 -86.1783 52.7969 52.7722
Subjectseconomic geology; igneous and metamorphic petrology; Science and Technology; mineral deposits; chromite; magmatic deposits; ore mineral genesis; mineralization; modelling; oxides; iron oxides; titanium; partial melting; iron formations; komatiites; chromium; magmas; fluid dynamics; Black Thor Intrusive Complex; Superior Province
Illustrationsmodels; plots; photomicrographs; schematic models
ProgramTargeted Geoscience Initiative (TGI-5) Nickel-copper-PGE-chromium ore systems - architecture - Cr-bearing systems
Released2019 01 18
AbstractMost magmatic chromite deposits, particularly those in stratiform layered ultramafic-mafic intrusions, are interpreted to have formed by processes that decrease the solubility of chromite. However, such models have difficulty in explaining the great thicknesses (up to 10 m) of chromite mineralization at Inyala and Railway Block (Zimbabwe), Ipueira-Medrado (Brazil), Uitkomst (South Africa), and Sukinda (India), and the very great (up to 100 m) thicknesses of chromitite at Kemi (Finland) and in the Black Thor Intrusive Complex (Canada). We propose a new process that involves partial melting of Fe ± Ti oxide-rich rocks (oxide-facies iron formation or ferrogabbro) and conversion of fine-grained oxide to chromite by reaction with Cr-rich komatiitic magma in a dynamic magma conduit. This process is analogous to the widely accepted model for the upgrading of barren iron-sulfide xenomelts to form magmatic nickel-copper-platinum group element deposits. We demonstrate that this process is geologically, physically, and chemically feasible, that it probably occurred in the Black Thor Intrusive Complex, and that it may have applications elsewhere.

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