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MORFOLOGIA DOS MINERAIS DE OURO E ARSENOPIRITA NO DEPÓSITO MARIA LÁZARA (GUARINOS, GOIÁS) E SUAS IMPLICAÇÕES NOS MECANISMOS DE DEPOSIÇÃO

1992; Sociedade Brasileira de Geologia; Volume: 22; Issue: 3 Linguagem: Inglês

10.25249/0375-7536.1992257261

2177-4382

GÊNOVA M. PULZ, ÉDER S. MARTINS, Reinhardt A. Fuck,

Geography and Environmental Studies

DEPOSITION MECHA-NISMS.Morphology of gold and arsenopyrite grains occurring in the hydrothermal alteration halo of the Maria Lázara deposit (Goiás) was studied using optical and scanning electron microscopy.Arsenopyrite displays deformational and recovery features associated with corrosion textures (dissolution microcavities) due to late stage percolation fluids.The gold minerals investigated show a wide variety of forms which indicate the precipitation mechanism that operated after intense metabasalt sulphidation.Textural and chemical relationships of the gold-arsenopyrite association demonstrate that gold deposition in the veins and the hydrothermal halo was independent from the deformation and metamorphism mechanisms of arsenopyrite and hydrotermalized matrix.Gold precipitation from hydrothermal fluid after the arsenopyrite deposition can be related with: 1. oxidation of hydrothermal fluid and, 2. electro-chemical reactions due to high conductivity of the sulphide surfaces.Gold minerals associated with the latest deposition stage exhibit abundant features on their surface, suggesting post-depositional changes in physico-chemical conditions of the hydrothermal fluid.These changes during the evolution of the hydrothermal system at the Maria Lázara gold deposit lead to remobilization processes resulting in the erratic distribution of gold grade within the ore zone.