Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

G. R. Gangadharan ¹, K. K. Achar ¹, K. Umamaheswar ¹, Mary K. Kumar ¹

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

Abstract

No Abstract.

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Ravi Kaul ¹, K. Umamaheswar ¹, S. Chandrasekaran ¹, R. D. Deshmukh ¹, B. M. Swarnkar ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, AMD Complex, Begumpet, Hyderabad 500 016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Uniara Gardens, Jawaharlal Nehru Road, Jaipur 302 004, IN

Abstract

The Siwalik Group constituting about 6000m of fluvial sedimentary rocks of Middle Miocene to Pleistocene age has been under exploration for uranium over the last two decades using different techniques including exploratory drilling, mining. More than 350 uranium occurrences forming eight major clusters between Poonch (Jammu, Kashmir) in the west and Tanakpur (Uttar Pradesh) in the east have been identified. A majority of these occurrences are confined to three distinct stratigraphic horizons: (1) lower part of Upper Siwaliks corresponding to the upper part of Garchandi energy sequence; (2) upper part of Middle Siwaliks (the middle part of Garchandi energy sequence); and (3) upper part of Lower Siwaliks (Jwalamukhi energy sequence).

Uranium mineralization occurs as small peneconcordant lensoid bodies with the longer dimension of individual lenses traceable from a few tens of metres to 700m, sub-parallel to strike or dip. The average grade of different occurrences in Siwaliks varies from 0.02-0.06% U₃O₈ and thickness less than a metre to 4m. Uraninite, pitchblende, coffinite, and a variety of secondary uranium minerals including tyuyamunite, uranophane, bayleyite, andersonite, schoepite, liebigite, swarlzite, and schroeckingerite have been identified. Azurite and malachite are also associated in some of the uranium occurrences in Lower Siwaliks. The sedimentological, geochrmical, and tectonic attributes of the Siwaliks indicate a sedimentary uranium province.

Uranium mineralization in Siwaliks is attributed to concentration of intrinsic uranium in the sediments derived from fertile Himalayan provenance and subsequent remobilisation by groundwater. Enrichment of uranium is controlled by sedimentary and lithological characteristics such as porosity-permeability barriers and abundance of reductants such as organic carbon, pyrite, and anaerobic bacteria. A secondary control by faults has also been observed at some places. Relatively higher concentrations of Se, Mo, Cu, Co, V, and Au have been noted in some of the uraniferous zones.

Keywords

Uranium Mineralization, Siwalik Group, North-Western Himalayas.

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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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S. Zakaulla ¹, H. S. Rajaraman ², A. P. Dhurandhar ³, R. Timothy ⁴, K. Umamaheswar ²

Affiliations
1 Atomic Minerals Directorate, Department of Atomic Energy, Bangalore, IN
2 Atomic Minerals Directorate, Department of Atomic Energy, Hyderabad, IN
3 Atomic Minerals Directorate, Department of Atomic Energy, Nagpur, IN
4 Atomic Minerals Directorate, Department of Atomic Energy, Shillong, IN

Abstract

In the Proterozoic Shillong Group, the Meso-Proterozoic arenaceous Barapani Formation, unconformably overlies the Paleo proterozoic Tyrsad Formation. Argillaceous quartz arenite, quartzite and quartz wacke are the constituents of Barapani Formation, in both Meghalaya plateau and Mikir Hilis in Assam. Samples from both the domains contain same type of detrital grains. Monocrystalline quartz forms about 70 to 90 % and feldspars and lithic fragments form minor part of the framework constituents. Sericite is the major mineral in matrix. Geochemical data (major and trace elements) of these arenites show overall similar elemental composition of all the samples from both Meghalaya plateau and Mikir Hills, Assam, indicating constancy of provenance. However, samples from the Mikir Hills as compared to that from Meghalaya Plateau show depletion in FeO(t), CaO, and MgO and enrichment in V, Cr, Co, Ni and Cu. Samples from both the Meghalaya plateau and Mikir Hills indicate a passive margin tectonic setting of sedimentation.

Keywords

Petrology, Geochemistry, Mid-Proterozoic, Barapani Arenite, Meghalaya, Mikir Hills, Assam.

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A. K. Dwivedi ¹, G. N. Hegde ², K. Umamaheswar ³

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Jamshedpur- 831 002, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Bangalore - 5 60 072, IN
3 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Shillong - 793 011, IN

Abstract

New occurrences of uranium mineralisation have been discovered in quartzite and siltsone/Shale units of the Gulcheru Quartzite Formation in the area to the north of E-W trending Idupulapaya fault around Idupulapaya, Malayalamma Bhavi, Tipparajupalle and Cheruvula Bodu. Mineralisation occurs in the form of lensoid bodies of 5 m x 0.5 m to 50 m x 1.5 m and is traced intermittently over an extent of 2000 m. Physical assay result of rock samples (n=66) has indicated values from 0.011% to 1.769% eU₃O₈, 0.017% to 1.848% U₃O₈ and <0.01% ThO₂. Samples (n=21) also analysed higher concentration of Cu (<25 ppm to 3202 ppm), Mo (<25 ppm to 472 ppm), Pb (<25 ppm to 2015 ppm), V (<25 ppm to 1010 ppm), Ag (<0.25 ppm to 3.92 ppm) and Au (<0.25 ppm to 1.40 ppm). Uranium minerals identified are uranophane, autunite, uranitite, pitchblende and U-Ti complex in association with pyrite, chalcopyrite, specular haematite and limonite. The above findings have opened up new potential target areas to look for uranium in the southwestern margin of Cuddapah basin.

Keywords

Uranium, Gulcheru Quartzite, Cuddapa Basin, Andhra Pradesh.

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S. Zakaulla ¹, K. Umamaheswar ², P. V. Tirupathi ¹, U. P. Sharma ¹, H. Basu ¹, M. A. Ali ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Nagarabhavi, Bangalore, IN
2 Atomic Minerals Directorate for Exploration and Research, Nagarabhavi, Shillong, IN

Abstract

Gulcheru Formation constitutes 200 m-250 m thick siliciclastic sediments Based on grain size texture and colour of the sediments, four distinct facies are demarcated They are pink massive quartzite, cross bedded grey quartzite, purple siltstone and pitted quartzite The ratios of Si/Al is higher (62 9 to 292 18) in pitted quartzite and lowest (2 122 - 18 247) in siltstone, where as grey quartzite has wide range of 3 78 - 8637 67 Ths difference is essentially due to higher quartz content in pitted quartzite and dominance of clays/shaly component in siltstone The wide range of Si/Al ratio in grey quartzlie is due to interlayering of siltstone/shale laminations/bands Distribution of uranium indicates grey quartzite (av U₃0₈= 9 9 ppm) and siltstone (av 15 42 ppm) have higher intrinsic uranium than that of pitted quartzite (average 5 6 ppm) and pink massive quartzite (average 7ppm) which is considered very high in comparison to normal sandstone (av = 0 5ppm, Taylor, 1965) Trace elements like Mo, V, Ni, Cu and Pb are enriched in mineralised grey quartzite Pitchblende is the man uranium mineral in grey and pitted quartzite unlts It occurs as fracture fillings and also as interstital material, associated intimately with chlorite Close association between pitchblende and sulphides like pyrite, chalcopyrite and galena is seen when pitchblende occurs as fracture fills Uranium in siltstone, is generally in adsorbed form with ferruginous material, where as associated trace elements like Mo (r = 0 515), V (r = 0 806), Nt (r = 0 4) and even Ti0₂, (r = 0 87) are well correlated with Al₂0₃, suggesting their clays/phyllosilicates U/Pb dating of uraniferous grey quartzite indicated ages of 1336k±4 Ma and 446±29 Ma suggesting remobilisation and concentration of intrinsic uranium.

Keywords

Gulcheru Formation, Cuddapah Supergroup, Siliciclastic Sediments, Uranium incidence, Gandi Area, Andhra Pradesh.

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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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M. B. Verma ¹, P. S. Dandele ², G. Nagendra Babu ², K. Umamaheswar ², P. B. Maithani ²

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

Abstract

Relationship of hydro-uranium anomalies (2-649 ppb) vis-a-vis underlying uranium ore body has been attempted based on seventy nine water samples collected from the exploratory boreholes on the northern periphery of Srisailam sub basin, Nalgonda district, A.P. Water table is hosted in the granitoid aquifer which underlies the cover rocks of Srisailam Formation. TDS (total dissolved salt) range from 123 to 1088 ppm (x^- = 329 ppm) and analyzed >500 ppm in eight samples. Water samples show a strong positive correlation of TDS with Cl^- (r=0.90), Na⁺ (r=0.82), Mg (r=0.80) and a moderate positive correlation with Sr (r=0.48) and Ca (r=0.70). Low value (<0.4) of Normalised Magnesium (NMg) indicates that host rock aquifer has not undergone chloritisation. Accumulate contour plan of uranium ore body shows NW-SE trend and coincides with the hydro-uranium contour. Correlation sections of ore body display true as well as false hydro-uranium anomalies in N-S and E-W profiles. Hydro-uranium anomalies owe their origin to uranium cations, dissolved from the mineralized horizon in to groundwater. Hydro-geochemical orientation survey carried out at Chitrial plateau may be applied regionally in the Srisailam sub basin as an effective tool to explore the concealed unconformity type uranium mineralization below Srisailam Formation.

Keywords

Hydrouranium Contours, Chitrial Plateau, Srisailam Formation, Accumulate Contour Map, Andhra Pradesh.

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D. K. Choudhury ¹, A. K. Pradhan ², S. Zakaulla ³, K. Umamaheswar ⁴

Affiliations
1 Atomic Minerals Directorate for Exploration & Research, Jamshedpur - 831 002, IN
2 Atomic Minerals Directorate for Exploration & Research, Shillong, IN
3 Atomic Minerals Directorate for Exploration & Research, Bangalore, IN
4 Atomic Minerals Directorate for Exploration & Research, Hyderabad, IN

Abstract

The granite in Samingiri - Dilsekgiri area occurs as discordant, isolated pluton within the migmatitic terrain of West Garo Hills district, Meghalaya. The pluton is exposed over 140 sq km (18 km × 8 km). It exhibits structures of solid state and piecemeal stoping effect proximal to the contact and enveloped by a contact metamorphic aureole of albite-epidote-hornfels facies. Modally, it is biotite-monzogranite and biotite-syenogranite with minor biotite, chlorite, epidote and sericite and accessories like zircon, apatite, allanite, pyrite, magnetite and sphene. Geochemically, it is marked by restricted composition (69-76 wt% SiO₂), high alkalies, low Ca, metaluminous to strongly peraluminous (Molar Al₂O₃/CaO+Na₂O+K₂O = 0.95-1.54), high FeO/MgO, high Ga/Al, high contents of Rb, Sr, Ba, Y, Zr and Ce and depleted in Ti and P. The field observation, mineralogical and geochemical aspects indicate the post-tectonic nature of West Garo pluton more like as A-type granite formed by partial melting of lower crustal blocks followed by low to moderate degree of fractional differentiation. Low Ca, alkaline nature and peraluminous character point to A-type nature of West Garo granite significantly different from other granites of Meghalaya Plateau. Rb-Sr age (616 ± 86 Ma) of granite, however, corresponds to widespread Middle to Upper Pan African activity, a thermal event prevailed during Late Proterozoic - Early Palaeozoic (500-800 Ma) period, manifested in the form of several granitic intrusions in the basement gneissic complex and the overlying Proterozoic metasediments of the Shillong Group in Meghalaya Plateau.

Keywords

West Garo Granite, Shillong Group, Meghalaya, Pan African Activity.

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