Portal de Periódicos da CAPES

Artigo Produção Nacional Revisado por pares

BIBTEX RIS

HONGSHIITE, PtCu, FROM ITABIRITE-HOSTED Au Pd Pt MINERALIZATION (JACUTINGA), ITABIRA DISTRICT, MINAS GERAIS, BRAZIL

2002; Mineralogical Association of Canada; Volume: 40; Issue: 2 Linguagem: Inglês

10.2113/gscanmin.40.2.711

1499-1276

Rogerio Kwitko-Ribeiro, Alexandre Raphael Cabral, Bernd Lehmann, J. H. Gilles Laflamme, L. J. Cabri, Alan J. Criddle, H. F. Galbiatti,

Geochemistry and Elemental Analysis

Hongshiite occurs associated with palladian gold, and more rarely with native platinum, in the sulfide-free, hematite-rich jacutinga mineralization of the Quadrilatero Ferrifero, central Minas Gerais, Brazil. Hongshiite occurs in grains up to about 1.5 mm in cross-section. The crystals (>0.1 mm) are generally covered by a porous rim from which copper is preferentially leached, eventually forming a rind of nearly pure native platinum. The morphological and chemical features of hongshiite are similar to features caused by the weathering of primary gold in a lateritic environment. Submicrometer-sized crystals, acicular in shape, replace an octahedral precursor phase, interpreted to be magnetite. The magnetite could have acted as a local redox barrier to the passage of oxidizing hydrothermal fluids leading to hongshiite precipitation. Sperrylite, isomertieite, atheneite, sudovikovite, a “guanglinite”-like phase, an undefined copper selenide, and barite occur as euhedral to anhedral inclusions in the larger crystals of hongshiite. Patches of a Au–Cu–Pt alloy within hongshiite have a composition nearly intermediate between tetra-auricupride and hongshiite, and could be called platinian tetra-auricupride, suggesting an extension of a solid solution toward hongshiite. The presence of tiny rosette-like crystals of native palladium in the auriferous jacutinga mineralization is also documented.