Clastic-volcaniclastic Rocks in Papaghni Sub-basin: Implications for Syn-sedimentary Felsic Volcanism during the Deposition of Paleoproterozoic Vempalle Carbonate Sequence, Cuddapah Basin, India

Based on detailed field, petrographic, mineral chemistry and geochemical studies, succinct details on the clastic - volcaniclastic sequence recorded within the dolomite horizon in Paleoproterozoic Vempalle Formation, Cuddapah basin, India are presented. The clastic rocks represented by rudaceous-arenaceous sequence and the volcaniclastic rock represented by an intervening tuffaceous horizon are noticed in the Vempalle dolomite near Tummalapalle area, in southwestern part of the Cuddapah basin. The conglomerate is matrix supported with dominantly chert clasts and the arenaceous unit is represented by fine grained quartz arenite. The tuffaceous unit is finely laminated exhibiting typical; clast matrix texture characteristic of fine grained pyroclastic rocks. Zircon, apatite, rutile and monazite are the accessory phases in the tuff. Geochemically, the felsic tuff is rhyolitic, peraluminous and shows relative enrichment of LREE. The chemical composition of the feldspar falls close to the K-feldspar end member in the Or-Ab-An plot. The clastic - volcaniclastic sequence in the Vempalle carbonate sequence indicate a localised break in carbonate precipitation accompanied by syn-sedimentary felsic volcanism during the evolution of Paleoproterozoic segment in the Cuddapah basin, India.