CARBON, OXYGEN AND URANIUM ISOTOPIC STUDY OF URANIFEROUS DOLOSTONE FROM CUDDAPAH BASIN, SOUTHERN INDIA - IMPLICATIONS TO DEPOSITIONAL ENVIRONMENT AND URANIUM ALTERATION
Sk. Bhattacharya et al., CARBON, OXYGEN AND URANIUM ISOTOPIC STUDY OF URANIFEROUS DOLOSTONE FROM CUDDAPAH BASIN, SOUTHERN INDIA - IMPLICATIONS TO DEPOSITIONAL ENVIRONMENT AND URANIUM ALTERATION, Journal of the Geological Society of India, 49(5), 1997, pp. 495-502
The dolostones show a narrow range of delta(13)C values but a large ra
nge of delta(18)O values. The small spread of delta(13)C from 0.1 part
s per thousand to -0.9 parts per thousand is typical of marine carbona
tes, whereas the large range of delta(18)O from -7 parts per thousand
to -14 parts per thousand represents characteristic Proterozoic marine
carbonates some of which were exposed to alteration by fresh continen
tal waters. A diagenetic environment of mixed marine and fresh water f
or the dolostone alteration is also supported by earlier studies in se
dimentary structures and petrography. The U-234/U-238 activity ratio o
f 0.7 in some of the mineralised samples shows the effect of ongoing c
hemical leaching of uranium from discrete uranium minerals like pitchb
lende and coffinite.