Carbon, Oxygen and Uranium Isotopic Study of Uraniferous Dolostone from Cuddapah Basin, Southern India : Implications to Depositonal Environment and Uranium Alteration

Abstract

The dolostones show a narrOw range of δ¹³C values but a large range of δ¹³O values. The small spread of δ¹³C from 0.1"° to -0.9"° is typical of marine carbonates, whereas the large range of δ¹³O from -7"° to -14"° represents characteristic Proterozoic marine carbonates some of which were exposed to alteration by fresh continental waters. A diagenetic environment of mixed marine and fresh water for the dolostone alteration is also supported by earlier studies in sedimentary structures and petrography. The ²³⁴U/²³⁸U activity ratio of 0.7 in some of the mineralised samples shows the effect of ongoing chemical leaching of uranium from discrete uranium minerals like pitchblende and coffinite.