S-ISOTOPIC STUDY ON BARYTE FROM THE ANDIYAPPANUR AREA, NORTH ARCOT DISTRICT, TAMIL-NADU

Sulphur-isotopic data on fifteen samples of baryte from the quartz-bar yte rock occurring along a shear zone east of the Elagiri Syenite plut on at Andiyappanur, Tamil Nadu have shown a narrow range of +5.1 parts per thousand to +9.5 parts per thousand, with an average of +6.70 par ts per thousand, for delta(34)S(CDT). The data, in conjunction with th e field and petromineralogical characteristics, indicate hydrothermal- type mineralisation of baryte. Association of relatively earlier forme d sulphides like pyrite, molybdenite and galena, and later formed sulp hates like baryte and jarosite in this quartz-baryte rock is attribute d to dual behaviour of sulphur in the magmatic-hydrothermal system, wi th formation of sulphides at depth under reducing conditions and of su lphates in the shallower oxidised zones.