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

Abstract

Charnockites and basic granulites occur extensively around Coorg in Western Ghats. Minor metasedimentary rocks like kyanite/sillimanite bearing gneisses and ironstone also occur. A set of late dolerite dykes cross cut all the lithologies.

The Coorg granulites record a near-peak metamorphic conditions of 720 to 760° C at pressures of 7 lo 8.6 kb. Charnockites and basic granulites contain high-density ( 1.07 to 1.09 g/cc) carbonic inclusions. Micro-textures, mineral P-T and fluid inclusion data indicate "clockwise" P-T trajectory, pointing to a relatively rapid uplift/erosion of the Coorg granulites.

Keywords

Full Text

Abstract

Fluid inclusion studies in migmatites around Hunsur document the presence of a) CO₂-CH₄, CO₂ and CO₂-H₂O inclusions in paleosome, b) predominantly CO₂ inclusions in leucosome and c) CO₂ and low salinity aqueous inclusions in late pink granite.

Chronological studies of CO₂ inclusions in quartz grains from migmatites and their densities corresponding to Th maxima plus mineral P-T data for the regional metamorphism indicate that they are syn-migmatitic fluids. An internal origin of CO₂ inclusions during the process of migmatization is envisaged.

Keywords

Full Text