Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Abstract

A small and economically unimportant molybdenite mineralization is found in the Peninsular gneisses around Yegawakote. Pyrite and chalcopyrite are the other ore minerals found associated with molybdenite. These minerals are found as fracture fillings in quartz veins.

Fluid inclusion studies on quartz carrying ore minerals reveal the presence of carbonic, through CO₂-H₂O, to entirely pure aqueous saline fluids. Microthermometric data show that most of the aqueous inclusions are in the salinity range of 4 to 15 wt%. NaCl have formed at temperatures of around 200-370 °C.

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Abstract

The Hutti greenstone belt, containing several promising gold deposits is predominantly composed of metavolcanics represented by basalt with minor felsic volcanics and metasediments. Basalt has undergone regional metamorphism as indicated by the presence of characteristic metamorphic mineral assemblage of plagioclase, amphibole and chlorite. Electron microprobe studies are carried out on these minerals to study the chemistry and the mineral reactions in the rock. The analytical data indicate that plagioclase is andesine, amphibole is magnesio-hornblende and chlorite is ripidolite.

The mineralogical assemblage, the chemistry and in particular the co-existence of hornblende and chlorite in metabasalt indicates a metamorphic grade 'transition between greenschist and amphibolite facies'.

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