[en] Factor analysis of multi-element data for Dhanjori conglomerates of Singhbhum district, Bihar, in eastern India reveals three factors accounting for about 57% of the total information contained in the data. Factors 1 and 2 are associated with radioactive elements. They also indicate that the provenance is a mixed felsic and mafic terrain, and that the minor and accessory constituents of these rocks are concentrated in the conglomerates. These two factors appear to result from the same sedimentological process. The factor-3 results from the V-Al diadochy. Factor-1 which is seen to be associated with both zircon and radioelements does not contain Pb. Pb is relegated to the factor-2. (author)

[en] The economic potentiality of the heavy minerals in the beaches between Baruva and Bavanapadu extending for about 45 km was examined. In the sub-surface sediments, the heavy minerals were studied at an interval of 1 m up to a maximum depth of 5.8m. In general the concentration of heavy minerals is high in dunes followed by backshore and foreshore regions. Heavy mineral content increases from surface to sub-surface in dunes, decreases in foreshore and does not vary much in backshore. The heavy minerals include mainly ilmenite, garnet, sillimanite and ortho-pyroxenes with minor amounts of amphiboles, zircon, monazite, rutile etc. Majority of the heavies such as ilmenite, monazite, zircon etc. are concentrated in finer fractions while some of the heavies like garnet and sillimanite are concentrated in coarser fractions. The inferred reserves estimated for the area indicate its economical potential. (author)

[en] Recent investigations by the Atomic Minerals Directorate for Exploration and Research, have brought into focus the presence of uranium mineralisation hosted by granite in its fracture zones, close to the unconformity in the Srisailam outliers in Lambapur, Peddagattu and Chitrial areas in the northern part of Cuddapah basin. Investigations further east of the Srisailam sub-basin have revealed good uranium mineralisation, both at the unconformity and in the overlying sediments of Banganapalle Formation of Kurnool Group in the Palnad sub-basin, around Koppunuru-Dwarakapuri. Further investigations southwest of these areas in the Kurnool sub-basin, have revealed significant uranium mineralisation in the Banganapalle Quartzite, intruded by vein quartz, close to the Gani-Kalva fault. This uranium discovery in the Kurnool sub-basin and some of its salient features, which have enhanced the uranium potentiality of the sub-basin as well as along the Gani-Kalva fault zone (55 km length and 2 km width) are reported here

[en] Platinum group elemental (PGEs-Pt,Ir,Pd,Rh and Ru) contents, determined by ICP-MS, are reported in a rare REE-Th-Zr-Ti-rich ultrabasic tremolite- actinolite rock from Vattalakki, Kerala. Data on PGE, together with unusually high contents of REE, Th, Zr and Ti at present level, indicate this rock as anomalous. (author)

[en] Carbon isotope studies on calcite-graphite system yield narrow Δ Cal-Gr values, varying from 3.9 to 4.3, indicating equilibrium between coexisting calcite and graphite. Calcite-graphite geothermometry has assigned temperatures ranging from 630 deg to 700 deg C for the cal-granulites found to the NE of Usilampatti area. The inferred temperatures correspond to the retrograde temperatures obtained by cation exchange thermometry on the granulites from other areas in the Madurai Block. These temperatures may correspond to the late isobaric cooling event. X-ray diffraction studies indicate well ordered nature of these graphites and corroborate the findings of isotope geothermometric influences. (author)

[en] 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. This 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 quartzite is due to inter layering of siltstone/shale laminations/bands. Distribution of uranium indicates grey quartzite (av. U₃O₈ = 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 7 ppm) which is considered very high in comparison to normal sandstone (av = 0.5 ppm, Taylor, 1965). Trace elements like Mo,V, Ni, Cu and Pb are enriched in mineralised grey quartzite. Pitchblende is the main uranium mineral in grey and pitted quartzite units. It occurs as fracture fillings and also as interstitial 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), Ni (r= 0.4) and even TiO₂ (r= 0.87) are well correlated with Al₂O₃ suggesting their association with clays/ phyllosilicate. U/Pb dating of uraniferous grey quartzite indicated ages of 1336±14 Ma and 446±29 Ma suggesting remobilisation and concentration of intrinsic uranium. (author)

[en] The Velugumetla barite deposit, Khammam district is studied for fluid inclusions, sulphur and strontium isotopes. The inclusions that are random in distribution and varying in size from 15-30 μ are classed as primary and the inclusions less than 15 μ in size and having linear trails as secondary. Heating runs of the primary and secondary inclusions show peaks at 235 deg C to 245 deg C(T_h) and 130 deg C to 140 deg C respectively. Both the primary and secondary biphase liquid rich(L+ V) inclusions homogenized by the disappearance of the vapour phase. The composition of fluid has been surmised as H₂O+NaCl+KCl. The salinity was calculated as 12.7 wt% NaCl eqv. The minimum depth of precipitation or barite was estimated to bc 300 m and the density calculated as 0.94g/cm³ with a fluid pressure of 31.2 bars. The fluid inclusion data of barite veins of vein barites of Velugumetla. Khammam district and other vein deposits of the Cuddapah Basin are correlatable in terms of composition, salinity, density, pressure, depth of entrapment and temperature of homogenization. The δ ³⁴S values for barite varies between +23.5 to+25.6 % and pyrite has values between -0.9 to + 1.9 % in case of the barite pyrite pairs that were studied from six different localities of the Cuddapah Basin and Khammam. The δ ³⁴S values of the vein barite deposits of the Cuddapah Basin and Khammam area are similar to the contemporaneous sea water. The strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios show wide variation 0.705 to 0.722 for the vein barites of Cuddapah Basin and Khammam and indicates significant contribution of radiogenic Sr from older continental crust. (author)

[en] The Precambrian migmatites around Kudri host uranium, rare earth and zirconium mineralization, manifested, respectively in the form of discrete uraninite, allanite and zircon. Mineralization is mostly in the biotite-rich melanosome (restite), albite-rich leucosome and mesosome (mobilizate). Uraninite with UO₂ content of 79.93-82.45% (av.81.36%), and content of high Th (ThO₂:2. 98-5. 71 %, av.4.37%) and high REE (RE₂O₃: 0.82-2.11, av.1.41 %) and chemical age (736- 929 Ma, av.824 Ma) of uraninite (n=14) point towards its origin during Neoproterozoic (av. 824 Ma), probably by epigenetic, high-temperature, synmagmatic origin which later subjected to dissolution and alteration by hydrothermal process. However, textural evidence of corrosion of erstwhile euhedral uraninite suggests its subsequent dissolution and alteration, together with expulsion of REE, possibly by a saline, moderately acidic hydrothermal (100-300 degC), reducing solution at a lower pressure, related to regional tectonic episode. (author)

[en] Significant sandstone-type uranium mineralisation is recorded from the Rongcheng Plateau and Rongdinala, located north and WNW of Balphakram Plateau, South Garo Hills district, Meghalaya. Mineralisation is associated with grey coloured, medium to coarse grained, poorly sorted arkosic Wacke-Subarkose suite of sandstones, belonging to the late Cretaceous Mahaek Formation. Sixteen uranium occurrences located 2-30 m above crystalline basement and with dimensions varying from 5 to 300 m x 0.5 to 4 m, have been identified. Grab samples have assayed up to 0.52% eU₃O₈, 0.46% U₃O₈ (beta/gamma) and <0.010% ThO₂. The fertile precambrian basement crystallines constitute the source of uranium. Presence of organic matter and pyrite in the sandstone provided reducing environment for deposition of pitchblende as the principal discrete uranium mineral. (author)

[en] Surface exploration techniques have been key contributors in discovering mineral deposits over the past three decades. However, in the last decade there has been a growing emphasis on integrating remote sensing, geological, geophysical and geochemical exploration techniques to compliment them in identifying concealed deposits. Successful integrated exploration requires putting mappable petrophysical property contrasts in terms of geological and geochemical process that could be associated with different mineralisation environment. The Precambrian Gangpur basin comprising volcanic free sedimentary sequence is considered as a potential geological setting for hosting uranium mineralisation. The Gangpur basin with metasediments of low to medium metamorphic grade classified as the Gangpur Group are known for hosting manganese, limestone and lead-zinc deposits. Uranium mineralization is reported in limonitic carbonaceous phyllite and sheared quartzite of Kumarmunda Formation at Jhamankele-Bhalulata areas. Several uranium anomalies have been associated with gossan at Kaedarpani, Jamdra and in ferruginised laterite at Badekachar, Jarmal, Jhagarpur, Kadorpani, Karamabahal, Tetelkela and Kumtinunda. In the present study geological, geophysical and remote sensing data sets are processed and integrated with other available data to delineate target zones for uranium exploration. Even though direct detection of uranium mineralisation remains unresolved in exploration strategy, instead it is becoming increasingly instructive to focus on mapping suitable depositional environments. The enhanced satellite imagery is interpreted in terms of thematic layers viz, trend lines, lineaments, faults and geological contacts. The aeromagnetic data is processed and interpreted thematic layers of magnetic breaks and linears from total magnetic intensity (TMI), the reduced to pole (RTP), tilt derivative and amplitude of analytical signal grid images. The radiometric data is processed based on their broad lithology and radio-elemental distribution maps viz, count maps, ratio maps, ternary (%K-eTh-eU) and eU/K - eU/eTh - eU images are generated to aid in mapping uranium favourability zones. The favourability image zones with high eU/K, eU/eTh and eU counts zones are classified into class based on statistics and anomalous high zones are picked up as uranium favourable locales. The thematic layers of geological contacts, lineaments and faults interpreted from satellite imagery, magnetic linears interpreted from aeromagnetic data and uranium favourability zone extracted from Airborne Gamma Ray Spectrometric (AGRS) data are overlaid. Based on spatial association exploration. of favourable features few locals are delineated for uranium exploration. (author)