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Stratiform and alluvial platinum mineralization in New Caledonia ophiolite complex

Thierry Auge and Pierre Maurizot
Stratiform and alluvial platinum mineralization in New Caledonia ophiolite complex
The Canadian Mineralogist (October 1995) 33, Part 5: 1023-1045

Abstract

The New Caledonia ophiolite contains two types of chromite deposits: podiform deposits in the mantle sequence and stratiform types in the cumulate sequence. Two types of PGE mineralization are associated: a typical Os-Ru-Ir association in the podiform chromite and a Pt-dominant association in the stratiform chromitite. In both types, the PGE enrichment is due to the presence of PGM trapped in chromite after crystallization from the melt. The constant association of chromite and PGM in chromite of the Pirogues cumulates suggests that PGM induced chromite nucleation. Thus chromite crystallization plays a major role in trapping and preserving the PGE mineralization. The levels enriched in chromite and PGE correspond with influxes of new magma into the chamber. PGM crystallization is promoted by the new conditions in which the melt finds itself, and is facilitated by low fS (sub 2) in the magma. The complex PGM assemblage in the Pirogues suite includes isoferroplatinum, tulameenite, undetermined Pt-Fe-Cu alloys, cooperite, Os-Ir-Ru alloy, laurite, bowieite, malanite, cuprorhodsite, sperrylite and base-metal sulphides with PGE in solid solution, and is explained as having formed under thermodynamic disequilibrium because the environment evolved rapidly in a closed system, with local changes in fO (sub 2) , fS (sub 2) and proportion of PGE without possible re-equilibration after entrapment in the chromite. The mineralized alluvium derived from primary mineralization shows solution features affecting certain grains, confirming a measure of PGE mobility during lateritic weathering. In Ni mineralized alluvium an even more complex assemblage results.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 33, Part 5
Title: Stratiform and alluvial platinum mineralization in New Caledonia ophiolite complex
Affiliation: BRGM "Metallogeny and Geodynamics", Orleans, France
Pages: 1023-1045
Published: 199510
Text Language: English
Summary Language: French
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 66
Accession Number: 1999-047046
Categories: Economic geology, geology of ore depositsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
S22°30'00" - S20°00'00", E164°00'00" - E167°00'00"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199916
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