Occurrence of Gold in the Mesoarchean Mayurbhanj Gabbros of Singhbhum Craton, Eastern India.

Singhbhum craton of eastern India is bestowed with several metal deposits such as iron, manganese, chromite, and platinum group of elements (PGE). Iron and manganese ores are associated with banded iron formations of Paleoarchean greenstone belts, and chromite and PGEs are associated with mafic-ultramafic rocks of Mesoarchean Baula- Nuasahi and Sukinda belts. Earlier studies indicate a hydrothermal origin of PGE mineralisation. Here, the occurrence of micron-sized gold grain and base metal sulfides in the Mesoarchean Mayurbhanj Gabrro Anorthosite Complex (GAC) are reported. These gabbros are considered coeval with Mayurbhanj granites and comprise of plagioclase, clinopyroxene and orthopyroxene, amphiboles, minor quartz, chlorite, and accessory opaque mineral phases. Scanning Electron Microscopic study shows the occurrence of a ∼3 µm sized sub-rounded gold spherule in feldspar, along with disseminated grains of sulphides of varying sizes. Geochemical analysis reveals that the Sarat-Ghat exposure of Mayurbhanj GAC contains an appreciable amount of gold and PGE (∑PGEs up to 1094 ppb and Au up to 396.5 ppb). The presence of sulphide minerals and intense alteration of feldspars and pyroxenes in the mineralised zone points towards a hydrothermal origin. This lithounit warrants a detailed appraisal to understand the nature and extent of gold and PGE mineralisation. [ABSTRACT FROM AUTHOR]