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Palladseite and its oxidation: evidence from Au-Pd vein-type mineralization (jacutinga), Cauê iron-ore mine, Quadrilátero Ferrífero, Minas Gerais, Brazil

Published online by Cambridge University Press:  05 July 2018

A. R. Cabral ,
B. Lehmann ,
R. Kwitko ,
H. F. Galbiatti  and
M. C. Pereira
A. R. Cabral*
Affiliation:
Institut für Mineralogie und Mineralische Rohstoffe, Technische Universität Clausthal, Adolph-Roemer-Str. 2A, D-38678 Clausthal-Zellerfeld, Germany
B. Lehmann
Affiliation:
Institut für Mineralogie und Mineralische Rohstoffe, Technische Universität Clausthal, Adolph-Roemer-Str. 2A, D-38678 Clausthal-Zellerfeld, Germany
R. Kwitko
Affiliation:
Centro de Desenvolvimento Mineral, Companhia Vale do Rio Doce, Rodovia BR 262 /km – 296 Caixa Postal 09, 33030-970 Santa Luzia-MG, Brazil
H. F. Galbiatti
Affiliation:
Diretoria de Metais Nobres, Companhia Vale do Rio Doce, 35900-900 Itabira-MG, Brazil
M. C. Pereira
Affiliation:
Diretoria de Metais Nobres, Companhia Vale do Rio Doce, 35900-900 Itabira-MG, Brazil
*
*E-mail: cabral@min.tu-clausthal.de
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Abstract

Palladseite (palladium selenide) and palladian gold occur as euhedral inclusions in specularite and as infill of microfractures and interstices in magnetite aggregates (host rock fragments) within specularite-rich auriferous veins (jacutinga). Palladseite has minor amounts of Pt (0.6–3.5 wt.%), Cu (2.9–3.5 wt.%), Hg (0.9–1.9 wt.%), and Ag (0.3–0.5 wt.%). The palladian gold contains up to 6 wt.% Pd, and minor Cu and Ag. Isomertieite (Pd11Sb2As2) and sudovikovite (PtSe2) are also recorded. The veins cross-cut the main tectonic foliation of the wallrock (itabirite). The feature of fracture infill and the Se-Sb-As-Hg-Cu-Ag geochemical/mineralogical signature of the Au-Pd mineralization point to a post-ductile deformation and possibly low-temperature (epithermal) origin of the jacutinga mineralization style.

Palladseite is replaced locally by a Pd-rich oxidation phase. Electron microprobe analysis of alteration halos around palladseite yields 76–80 wt.% Pd. Oxygen calculated by stoichiometry accords with a monoxide compound of the type PdO. However, the measured oxygen content is lower than expected for the PdO stoichiometry, suggesting loss of volatile species, and a more ‘hydrated’ compound, such as an oxyhydroxide.

Keywords

palladseite alterationPd-O speciespalladian goldsudovikovitejacutingaCauê iron-ore mineItabira Iron FormationQuadrilátero FerrõferoBrazil
Type
Research Article
Information
Mineralogical Magazine , Volume 66 , Issue 2 , April 2002 , pp. 327 - 336
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

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