Petrography and Fluid Inclusion Studies on Late Proterozoic Palnad Siliciclastics, Kurnool Group, Andhra Pradesh

Petrographic studies of Palnad siliciclastics reveal medium to fine grained, sub rounded to rounded detrital quartz grains cemented by silica mostly as authigenic overgrowth. Fluid inclusions trapped in the quartzites of Kurnool Group (Palnad Basin) are of aqueous saline type. The melting temperature indicates salinity values of 5-17.2 wt % NaCl equivalent and the density of these saline fluids vary from 0.889-0.952 gcm³. The entrapment of fluids in quartz grains took place between the temperature range of 76.5° to 202°C. Petrography and microthermometric data of these quartzites points to granites and granitic gneisses as the source rocks. The presence of secondary inclusions indicates probable tectonic activity during the deposition of the sediments in the study area.