FLUID-FLOW DURING CONTACT-METAMORPHISM - PETROGRAPHIC EVIDENCE FROM THE URANIUM PROSPECT AT TUMMALAPALLE IN THE SOUTHWESTERN PART OF CUDDAPAH BASIN, INDIA

In the uranium prospect at Tummalapalle in the southwestern part of Cu ddapah basin, fluid flow during contact metamorphism is documented in a vein-mineral-assemblage of a metadolerite intruding the carbonate ro cks and shale of the Vempalle Formation of the mid-Proterozoic Lower C uddapah Supergroup. The minerals in the vein are calcite, quartz, Mg-c hlorite and Fe-chlorite formed in that order due to fluid-infiltration -driven volatilization reactions involving CO2- and H2O- fluid having an external source in the nearby sedimentary rocks. The observed seque ntial vein-mineral assemblage is considered as a petrographic evidence of 'infiltrating fluid mechanism during metamorphism', proposed first by Ferry (1980), as well as for 'batch volatilization' of Valley (198 6).