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The Serra Pelada Au-Pd-Pt Deposit, Carajás Mineral Province, Northern Brazil: Reconnaissance Mineralogy and Chemistry of Very High Grade Palladian Gold Mineralization

A. R. Cabral and B. Lehmann

Institut für Mineralogie und Mineralische Rohstoffe, Technische Universität Clausthal, Adolph-Roemer-Strasse 2A, D-38678 Clausthal-Zellerfeld, Germany

R. Kwitko

Companhia Vale do Rio Doce—CVRD, Centro de Desenvolvimento Mineral, Rodovia BR 262/ km 296, Caixa Postal 09, 33030-970 Santa Luzia-MG, Brazil

C.H. Cravo Costa

Companhia Vale do Rio Doce—CVRD, Diretoria de Metais Nobres, Caixa Postal 51, Serra dos Carajás, 68516-000 Parauabepas-PA, Brazil

Corresponding author: email, lehmann{at}min.tu-clausthal.de

A historic drill core from the Serra Pelada open pit was only recently assayed and has spectacular gold, palladium, and platinum grades over a 43-m-depth interval (4,709 g/t Au, 1,174 g/t Pd, 204 g/t Pt). The Au-Pd-Pt mineralization in a bonanza-grade interval (54.5–55.0 m @ 132,000 g/t Au, 11,400 g/t Pd, 359 g/t Pt) consists of coarse-grained, up to several centimeter-large, dendritic palladian gold aggregates (Au₇Pd) with abundant inclusions of guanglinite (Pd₃As), "stibio-guanglinite" (Pd₃[As,Sb]), sudovikovite (PtSe₂), palladseite (Pd₁₇Se₁₅), and an unnamed Pd-Pt-Se alloy. The palladian gold aggregates are often coated by goethite and are embedded in a powdery, ferruginous, clay-rich matrix with fragments of vein quartz. Iron and manganese oxides occur as vug fillings in palladian gold and are associated with native palladium and Pd-oxygenated compounds.

The near-surface bonanza palladian gold mineralization is part of a larger, deeply weathered, hydrothermal system which, in deepest drill holes (>300 m), has a relict sulfide assemblage with a variable degree of overprint by iron oxides, sericite, and kaolinite. The deep system still has gold, palladium, and platinum grades in the g/t range and displays erratically high contents in light rare earth elements, bismuth, and selenium. Drill core samples from intermediate depth (157–275 m) are high in gold, palladium, and platinum and show a very pronounced bismuth enrichment, as well as enrichment in iridium, mercury, rare earth elements, uranium, copper, and lead. The shallow drill core is extremely enriched in gold, palladium, platinum, mercury, and manganese.

The occurrence of gold dominantly as an Au-Pd alloy, the abundant selenide and arsenide inclusions in palladian gold, and the characteristic mercury signature point to an origin of the near-surface bonanza ore from a sulfur-deficient hydrothermal system, with apparently only minor supergene precious metal enrichment.

This article has been cited by other articles:

				A. R. Cabral, G. Beaudoin, R. Kwitko-Ribeiro, B. Lehmann, J. C. Polonia, and M. Choquette PLATINUM PALLADIUM NUGGETS AND MERCURY-RICH PALLADIFEROUS PLATINUM FROM SERRO, MINAS GERAIS, BRAZIL Can Mineral, April 1, 2006; 44(2): 385 - 397. [Abstract] [Full Text] [PDF]

				A. R. Cabral, A. R. Cabral, and B. Lehmann A two-stage process of native palladium formation at low temperatures: evidence from a palladian gold nugget (Gongo Soco iron ore mine, Minas Gerais, Brazil) Mineralogical Magazine, June 1, 2003; 67(3): 453 - 463. [Abstract] [Full Text] [PDF]

				B. Lehmann, J. Mao, S. Li, G. Zhang, and M. Zeng aRe-Os DATING OF POLYMETALLIC Ni-Mo-PGE-Au MINERALIZATION IN LOWER CAMBRIAN BLACK SHALES OF SOUTH CHINA AND ITS GEOLOGICAL SIGNIFICANCE--A REPLY Economic Geology, May 1, 2003; 98(3): 663 - 665. [Full Text] [PDF]

				A. R. Cabral, B. Lehmann, R. Kwitko-Ribeiro, R. D. Jones, and O. G. Rocha Filho ON THE ASSOCIATION OF PALLADIUM-BEARING GOLD, HEMATITE AND GYPSUM IN AN OURO PRETO NUGGET Can Mineral, April 1, 2003; 41(2): 473 - 478. [Abstract] [Full Text] [PDF]

				A. R. Cabral, B. Lehmann, R. Kwitko-Ribeiro, and C. H. C. Costa PALLADIUM AND PLATINUM MINERALS FROM THE SERRA PELADA Au-Pd-Pt DEPOSIT, CARAJAS MINERAL PROVINCE, NORTHERN BRAZIL Can Mineral, October 1, 2002; 40(5): 1451 - 1463. [Abstract] [Full Text] [PDF]