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 Cuddapah basin, fluid flow during contact metamorphism is documented in a vein-mineral-assemblage of a metadolerite intruding the carbonate rocks and shale of the Vempalle Formation of the mid-Proterozoic Lower Cuddapah Supergroup. The minerals in the vein are calcite, quartz, Mg-chlorite 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 sequential 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 (1986).