Original paper

Gold and uranium contents in gypsum formed from percolating ground water in a Witwatersrand-like gold deposit, Ouro Fino, Minas Gerais, Brazil: LA-ICPMS data

Koglin, Nikola; Cabral, Alexandre Raphael; Brunetto, Wilson José; Brätz, Helene

Abstract

Results of measurements on gypsum for gold (Au) and uranium (U) using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) are reported. The Au contents were mostly below the average detection limit of 0.07 μg/g, with a maximum value of 0.20 μg/g Au, whereas the U concentrations vary from 0.04 to 1.82 μg/g. The gypsum formed from the weathering of auriferous pyrite in a Witwatersrand-like gold deposit, Ouro Fino, Minas Gerais, Brazil. The pyrite exposed along exploration adits was extensively dissolved in about 25 years by percolating ground water. The LA-ICPMS results indicate that gold has not followed the sulfate pathway during the weathering of auriferous pyrite. Compared to gypsum from continental evaporitic environments, the Ouro Fino gypsum shows some enrichment in U, which likely reflects its uraniferous Witwatersrand-like setting.

Keywords

gypsumgolduraniumla-icpmswitwatersrand-like metaconglomerateouro finomoeda formationminas geraisbrazil