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Platinum-palladium nuggets and mercury-rich palladiferous platinum from Serro, Minas Gerais, Brazil

Alexandre Raphael Cabral, Georges Beaudoin, R. Kwitko-Ribeiro, Bernd Lehmann, Jose Carlos Polonia and Marc Choquette
Platinum-palladium nuggets and mercury-rich palladiferous platinum from Serro, Minas Gerais, Brazil
The Canadian Mineralogist (April 2006) 44, Part 2: 385-397

Abstract

Arborescent, botryoidal and reniform grains of platinum and palladium from Corrego Bom Sucesso, Serro, Minas Gerais, Brazil, were investigated by scanning electron microscopy and electron-microprobe analysis. The nuggets reach a maximum length of 2.5 mm and exhibit core-to-rim compositional zoning in platinum, palladium and mercury contents. One grain is noteworthy for a marginal halo of mercury-rich palladiferous platinum and internal vermiform lamellae enriched in mercury and gold. The mercury-rich palladiferous platinum has 10-20 wt% Hg and an empirical stoichiometry close to (Pt,Hg) (sub 2) Pd. Hexagonal crystals occur in palladiferous platinum forming a peripheral zone of an arborescent grain. These crystals are compositionally analogous to stoichiometric PdPt and seem to represent an ordered phase distinct from either platinum or palladium. Most Pt-Pd grains have dissolution pits, suggesting that they are primary nuggets that have been weathered. Anatase, with or without intergrowth of gold, and Na-K-Cl-bearing aggregates postdate the Pt-Pd nuggets. Selenium is a minor alloying constituent (up to 0.3 wt%) in the Pt-Pd nuggets. The ratio S:Se is <1 and suggests fractionation of selenium from sulfur under low-temperature oxidizing conditions. Such oxidizing conditions are reflected in the Fe-poor bulk composition of the alloys. The Pt-Pd nuggets from Corrego Bom Sucesso are consistent with the observation that almost all economically important Brazilian Pd-Pt-bearing deposits associated with gold or hematite (or both) have a distinctive seleniferous signature.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 44, Part 2
Title: Platinum-palladium nuggets and mercury-rich palladiferous platinum from Serro, Minas Gerais, Brazil
Affiliation: Universite Laval, Departement de Geologie, Quebec City, QC, Canada
Pages: 385-397
Published: 200604
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 54
Accession Number: 2007-005992
Categories: Mineralogy of non-silicatesEconomic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
S23°30'00" - S14°00'00", W51°00'00" - W39°45'00"
Secondary Affiliation: Centro de Desenvolvimento Mineral, BRA, BrazilTechnische Universitaet Clausthal, DEU, Federal Republic of Germany
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200702
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