The Proterozoic Cuddapah basin is a well established U province of India. Both the sediments and the basement granitoids of this basin are characterized by higher abundances of intrinsic U. Remobilization of this intrinsic U had presumably played a role in the formation of the deposits found in this basin. While intrinsic U in the granitoids is controlled mainly by the factors of igneous crystallization, in siliciclastics it is contributed from the detrital and the authigenic (non-detrital) sources. Authigenic U in fine siliciclastics is generally determined by estimating its detrital U with reference to the Th/U ratio of a reference rock. Considering the influence of sedimentological factors like recycling, mixing, hydraulic sorting on Th and the differential chemical stability of U and Th in the near-surface depositional conditions, detrital proxies viz. Al and Ti are taken here for estimating the detrital U.

Authigenic U in the mudrocks of the Gulcheru Formation is estimated at 3.33 ppm and 4.03 ppm with reference to the Th/U and the U/Ti ratios, respectively, of the average Proterozoic cratonic shale. Considering the differences in the stability of Th and U in the sedimentary domain, the former is taken as lower and the latter as higher estimates. The redox-sensitive metal ratios (Ni/Co, V/Cr) indicated that U authigenesis in the Gulcheru Formation took place mainly in oxic-dysoxic water. This study also elucidates the bearing of authigenesis on the elevated intrinsic U abundances in the mudrocks of the Gulcheru Formation.

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