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A. K. Rai ¹, Himadri Basu ², S. Zakaulla ¹, K. Umamaheswar ²

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Bangalore-560072, IN
2 Atomic Minerals Directorate for Exploration and Research, Hyderabad-500016, IN

Abstract

Miniature pits of varying size and shape are found in the topmost arenaceous layers of the Gulcheru quartzite. Though pits in sedimentary rocks form in a variety of ways, in clean beach sands they owe their origin to mainly physical processes. Small pits, found in the Gulcheru quartzite, have been formed as a result of interplay of difierent physico-Chemical factors which prevailed in syn- as well as post-Depositional environments. In addition to different agents of physical weathering, which played a vital role in the formation of pits in the Gulcheru quartzite, syn-depositional precipitation of iron oxides and their syn-to post-diagenetic chemical changes are believed to be the main chemical factors.

Keywords

Pits, Ferric-Hydroxide, Gulcheru Quartzite, Cuddapah Basin, Andhra Pradesh.

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Himadri Basu ¹, G. R. Gangadharan ¹, Suresh Kuman ¹, U. P. Sharma ¹, A. K. Rai ¹, Anjan Chaki ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Nagarbhavi, Bangalore 560 072, IN

Abstract

Middle Proterozoic Gulcheru Quartzite marks the onset of sedimentation, after the Eparchaean unconforrnity, in the Cuddapah Basin. In the southwestern margin of the basin it is made up dominantly of orthoquartzites. On the basis of lithology, stratigraphic relationship, bedding characteristics, texture and colour of sediments and sedimentary structures, five lithofacies were recognized within Gulcheru Quartzite. The Gulcheru Quartzite, though dominantly of shallow marine origin, shows imprints of other depositional regimes. Detailed interpretation of the facies and study of their field relationships reveal that pink massive quartzite, the lowermost unit of Gulcheru Quartzite, is of fluvio-aeolian origin. Later marine transgression .led to the development of a moderate to low energy beach, which evolved with time into a barrier: spit complex.

Keywords

Depositional environment, Facies analysis, Fluvio-Aeolian, Barrier-Spit, Gulcheru Quartzite, Cuddapah Basin, Andhra Pradesh.

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Himadri Basu ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Hyderabad - 500 016, IN

Abstract

No Abstract.

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K. Umamaheswar ¹, Himadri Basu ¹, J. K. Patnaik ¹, Mir Azam Ali ¹, D. C. Banerjee ²

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Bangalore-560 072, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Hyderabad-500 016, IN

Abstract

Significant uranium occurrences are discovered recently for the first time in the Gulcheru Quartzite of Papaghni Group of Cuddapah Supergroup near Gandi, east of Papaghni river, Cuddapah District, A.P. Mineralisation is associated with an E-W fault. Friable whitish to light pink quartzite is the main host rock of uranium. Mineralisation occurs in the form of lensoidal bodies having dimensions of 20 - 200 m x 2 - 10 m in an E-W fault scarp section, over 2 km in length. Dip section is also mineralised. Samples have revealed anomalous concentrations of uranium, up to 1.441% U₃O₈ with negligible thorium. Concentration of Ni (<25 to 1033 ppm), Mo (<25 to 643 ppm), Pb (33 to 1515 ppm) and Cu (<25 to 170 ppm) points to the economic potentiality of the area. Petrological studies have identified uranium minerals such as pitchblende, uraninite and coffinite as fracture fillings and disseminations in the chlorite-sericite matrix of quartzite. The associated ore minerals are chalcopyrite, arsenopyrite, pyrite and limonite. These findings have important implications in the selection of new exploration targets for uranium in the basal beds of Cuddapah Supergroup unconformably overlying the fertile granitoid basement in the Eastern Dharwar Craton occurring in the southwestern part of Cuddapah basin.

Keywords

Uranium Mineralisation, Gulcheru Quartzite, Cuddapah Basin, Andhra Pradesh, Dharwar Craton.

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Himadri Basu ¹, K. Mahendra Kumar ², S. Paneerselvam ³, A. Chaki ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Hyderabad - 500 016, IN
2 Atomic Minerals Directorate for Exploration and Research, Jamshedpur - 831 002, IN
3 Atomic Minerals Directorate for Exploration and Research, Bangalore - 560 072, IN

Abstract

Provenance studies on the basis of U, Th and K reveal that the sediments of the Gulcheru Formation were derived from a minor heterogeneous but dominantly granitoid provenance, which often underwent moderate chemical weathering. Mixing of reworked and heavy mineral bearing matured sediments with newly generated detritus took place at different times. Sedimentation took place in three different phases. Initially the sediments were deposited in fluvioaeolian environment. Later, subsidence of the depo-centre along basinal growth faults led to the transgression of seawater over earlier sediments. The last phase of the sedimentation history continued in the marginal marine domain. The depocentre most possibly experienced semi-arid climate.

Keywords

U, Th And K Abundances, Provenance Characteristics, Depositional History, Gulcheru Formation, Cuddapah Basin, Andhra Pradesh.

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