SULFUR ISOTOPIC STUDY ON THE VEIN-TYPE BARYTE FROM VEMULA IN THE VEMPALLE FORMATION OF CUDDAPAH BASIN, ANDHRA-PRADESH

Baryte at Vemula near to the southwestern margin of Cudapah Basin occu rs as a vein-type deposit discordant to both the carbonate rocks of Ve mpalle formation and its intrusive dolerite. S-isotopic data on the ba ryte have a range of delta(34)S(CDT), between +16.2 parts per thousand and +23.3 parts per thousand whereas the coexisting chalcopyrite has a restricted range between +10.9 parts per thousand and +11.4 parts pe r thousand. The average value of delta(34)S of Vemula baryte (+20.8 pa rts per thousand) differs much from that of magmatic rocks (0 parts pe r thousand to +2.5 parts per thousand), metamorphic rocks (+3 parts pe r thousand) and sediments of continental margins, platform areas and g eosynclines (-12.5 parts per thousand -17.1 parts per thousand), but i s similar to that of sea water (+20 parts per thousand) which appears to be the source for sulphur. The narrow range of delta(34)S of baryte and chalcopyrite points to a uniform source with their sulphur possib ly derived from sea water sulphate by bacteriogenic reduction.