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Palladium minerals from the Cauê iron mine, Itabira District, Minas Gerais, Brazil

Published online by Cambridge University Press:  05 July 2018

Gema Ribeiro Olivo  and
Michel Gauthier
Gema Ribeiro Olivo
Affiliation:
Université du Québec à Montréal, Département des sciences de la terre, case postale 8888, succ. A, Montréal, PQ, Canada, H3C 3P8
Michel Gauthier
Affiliation:
Université du Québec à Montréal, Département des sciences de la terre, case postale 8888, succ. A, Montréal, PQ, Canada, H3C 3P8
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Abstract

Palladium-bearing minerals from the Cauê iron mine, Itabira District, Minas Gerais, Brazil, are found in gold-rich jacutinga, a hydrothermally-altered Lake Superior-type carbonate-bearing oxide facies iron-formation. Palladium occurs as: native palladium with trace contents of Au, Fe and Cu; palladseite ((Pd,Cu,Hg)17Se15), which was found in the core of a grain of palladium; palladium–copper oxide ((Pd,Cu)O); and arsenopalladinite (Pd8(As,Sb)3), with inclusions of palladium–copper oxide. The palladium and palladium–copper oxide grains are coated with films of gold and commonly do not exceed 100 µm in width. These palladium minerals occur in hematite bands and in boudinaged bands of quartz and white phyllosilicate parallel to the S1 mylonitic foliation. Palladium-copper oxide also occurs as inclusions in gold grains which are strongly to weakly stretched parallel to S1.

Palladium mineralization is interpreted as synchronous with intense D1 shearing and contemporaneous with the peak of thermal metamorphism. At high oxygen fugacities and high temperatures (up to 600°C), Pd may have been transported as chloride complexes and deposited following changes in pH caused by mineralizing fluids reacting with jacutinga. Deposition may also have been prompted by the formation of insoluble selenide and arsenide–antimonide minerals and by the dilution of C1 concentrations in the mineralizing fluid. Textural studies, and the zonation observed in palladium and other hydrothermal minerals, suggest that oscillations in the physico-chemical conditions of hydrothermal fluids occurred during the mineralizing event.

Keywords

palladium mineralspalladseitearsenopalladiniteCaué mineBraziljacutinga
Type
Mineralogy
Information
Mineralogical Magazine , Volume 59 , Issue 396 , September 1995 , pp. 455 - 463
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1995

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