Provenance and genesis of the auriferous palaeoplacer deposits in the Palaeoproterozoic Moeda Formation, Minas Gerais, Brazil

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The Palaeoproterozoic Moeda Formation of the Quadrilátero Ferrífero in Minas Gerais (Brazil) consists of several conglomerate/quartzite units with economic gold grades in some conglomerate beds. These deposits bear strong similarities to palaeoplacer deposits elsewhere in the world where they are known for their enormous economic potential for both gold and uranium. The prime example is the famous Archaean Witwatersrand Basin in South Africa, which hosts about 40% of all known minable gold in the world. The success of any future exploration is invariably dependent on a sound genetic model. The goal of this project is, therefore, to reconstruct the genesis of the gold deposits in the Moeda Formation using modern analytical techniques and applying existing experience with the Witwatersrand deposits. The principal questions to be addressed are whether the gold came into the host conglomerate originally as detrital particles ¿ analogous to the Witwatersrand deposits ¿ and, if that was the case, where the source(s) of that detrital gold was (were) located, and moreover to which extent gold was (re-)mobilised by post-depositional metamorphic/hydrothermal fluids. To this effect geological fieldwork, petrological and lithogeochemical analyses, multiple sulphur isotope studies and trace element analyses of gold, selected sulphides and silicates are planned. This will be complemented by a comparative study on the gold deposits in the adjacent Rio das Velhas Greenstone Belt because they appear to be the closest equivalents to likely source(s) of the detrital sulphide and gold particles in the Moeda Formation conglomerates. Overall the expected results will help considerably in improving our understanding of this economically most important type of conglomerate-hosted gold (and uranium) deposits worldwide.