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

Abstract

Universit6 du Qu6bec ~t Montr6al, D6partement des sciences de la terre, case postale 8888, succ. A, Montr6al, PQ, Canada, H3C 3P8 AbstractPalladium-bearing minerals from the Cau~ iron mine, Itabira District, Minas Gerais, Brazil, are found in goldrich 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,HghTSeis), which was found in the core of a grain of palladium; palladium-copper oxide ((Pd,Cu)O); and arsenopalladinite (Pds(As,Sb)3), with inclusions of palladium-copper oxide. The palladium and palladiumcopper oxide grains are coated with films of gold and commonly do not exceed I00 p,m 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 S 1. Palladium mineralization is interpreted as synchronous with intense DI shearing and contemporaneous with the peak of thermal metamorphism. At high oxygen fugacities and high temperatures (up to 600~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 CI 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.

On the Rosettes of "Native Palladium" From Minas Gerais, Brazil: Evidence From Gongo Soco

“…The occurrence of native palladium as a mineral species was noted for the first time in the early 1800s, when Wollaston (1809) investigated samples from gold mines in Brazil, possibly from Minas Gerais [vide Atencio (2000) for a discussion of the provenance of the samples]. Hussak (1904) detected grains of native palladium in residual concentrates from the gold washing at Itabira, later identified by electron-microprobe analysis (Olivo & Gauthier 1995). Also at Itabira, rosette-like crystals of native palladium were found on a crust of iron oxyhydroxide on Pd-bearing gold (Kwitko et al 2002).…”

Palladian gold and palladium arsenide–antimonide minerals from Gongo Soco iron ore mine, Quadrilátero Ferrífero, Minas Gerais, Brazil

“…21 Both Itabira and Gongo Soco are hosted by itabirite and they dislay a similar palladium gold assemblage of specularite and palladium arsenide-antimonide and selenide minerals. 5,6,8,9,[33][34][35][36] The jacutinga orebodies from Itabira have been considered by Olivo et al [33][34][35][36] as parallel to the tectonic foliation of the host itabirite. However, recent detailed geological mapping by mine geologists has disclosed that, like Gongo Soco, the jacutinga orebodies occur as crosscutting veins, 14 whereas further mineralogical investigation has indicated a mineral association compatible with temperatures in the epithermal range.…”

THE SYSTEM Hg-Pd-Se AT 400 C: PHASE RELATIONS INVOLVING TISCHENDORFITE AND OTHER TERNARY PHASES

“…The association of selenides at Minais Gerais and Serra Pelada in Brazil (Davis et al 1977, Olivo & Gauthier 1995, Cabral et al 2002, Cabral & Lehmann 2007 consists of the following minerals: palladseite, sudovikovite, chrisstanleyite, and jacutingaite. Palladium selenides also were observed in carbonaceous Precambrian black shale in the Voronezh crystalline massif in Russia (Rudashevskiy et al 1995).…”