Magmatic Type Platinum Mineralisation in the Mafic-Ultramafic Rocks of Nuggihalli Schist Belt, Hassan District, Karnatak

The layered ultramafic complex of Nuggihalli schist belt in the western Dharwar craton (Karnataka) comprises dismembered units of serpentinised peridotites and metapyroxenites with discontinuous chromitite reefs, gabbroic amphibolites (± garnet) with seams of titaniferous-vanadiferous magnetite and anorthosites. Cumulus and intercumulus chromitite forming discrete lenses within the serpentinites are confined to two distinct zones at least in the central part of the schist belt from Byrapura in the north to Tagadur in the south. Since Archaean chromiferous layered complexes are considered as best repositories of PGE mineralisation, search for PGE in Nuggihalli ultramafics have been carried out time and again but for little success. The present write up is the first systematic approach to assess the possibilty and reports for the first time significantly high concentration of Pt+Pd up to 2.5 ppm. This is the highest PGE value recorded from Nuggihalli belt till date. Sample having anomalous PGE has also analysed Au up to 270 ppb. The finding of high PGE concentration (1.5 to 2.5 g/t) in two zones of 1m each from the gabbroic anorthosite having thin bands of magnetite(TVM) on the western margin of the Nuggihalli schist belt at Kamanayakanahalli opens up new possibilities of searching for PGE-rich zones in similar mafic-ultramafic sequences of Karnataka.