[en] The paper deals with the geology, petromineralogy, geochemistry and potentiality of the rare metal and rare earth-bearing pegmatites in the states of Karnataka, Andhra Pradesh and Tamil Nadu, southern India. The rare metal and rare earth-bearing pegmatites in Karnataka are of lithium-cesium- tantalum (LCT) type whereas those in Andhra Pradesh and Tamil Nadu appear to be essentially niobium-yttrium-fluorine (NYF) type. Weathering of all these pegmatites has resulted in concentration of rare metal and rare earth minerals in the alluvial, eluvial and delluvial placers from which tens of tonnes of the minerals like niobian-tantalite, tantalo-columbite, beryl, spodumene, etc., are being recovered by gravity separation techniques

[en] Aeromagnetic data over a part of the Singhbhum Uranium Province covered under 'Operation Hard Rock' have been analysed. Aeromagnetic anomaly map generated from the high-resolution data, its analytical signal and the Euler solutions helped in identifying the nature and depth of the magnetic sources in the study region. The Singhbhum Shear Zone is clearly demarcated and the known uranium deposits/occurrences fall on the identified shallow magnetic sources. Distinctive magnetic sources have been identified in the central part of the zone, lying between the Dalma volcanics and the Chotanagpur Granitic Gneissic Complex. The sources in this zone are shallow and depict similar magnetic characteristics as that of the Singhbhum Shear Zone, and may indicate zone of concealed uranium deposit that can be explored in the future. The analysis shows the importance of conducting high-resolution aeromagnetic surveys and how a proper systematic analysis of aeromagnetic data can be useful in the identification of concealed mineral deposits. (author)

[en] Proterozoic Shillong Basin of Meghalaya comprises metapelites of Paleoproterozoic Tyrsad and arenaceous siliciclastics of Mesoproterozoic Barapani formations. Two major igneous activities, in the form of basic dykes/sills and younger granites of Neoproterozoic age, intruding Proterozoic sediments, are reported from Shillong Basin. Significant uranium mineralisation, with values up to 0.1% U_3O_8, associated with NE-SW trending shear zone in Barapani Formation is discovered at Mawbeh area, Pynursla Plateau. The mineralised Barapani has undergone hydrothermal alterations in the form of sericitisation, chloritisation, illitisation and kaolinisation. Petrographic studies reveal that the host rocks are ortho-quartzite, subfeldspathic arenites, quartz wacke, sericite phyllite, quartz-sericite-chlorite rock and quartz wacke. X-ray diffraction (XRD) studies of radioactive Barapani quartzite revealed the presence of uraninite. (author)

[en] Radioactive sand stone samples of sedimentary rocks constitute fine particles like clays, hydrous iron oxides (goethite) and humic acid. All these colloidal particles have the property of sorption, ion-exchange etc. under suitable conditions. Hence the ability of these fine particles for uranium sorption and retention has been investigated in detail individually on ferric hydroxide gel, goethite and humic acid gel and the thermoanalytical studies were also carried out. Freshly precipitated ferric hydroxide gel exhibited uranyl sorption upto 9%. Natural and synthetic goethite showed upto 2.8%, and humic acid upto 6% under optimum conditions of pH and uranyl concentration. Differential thermal analysis was carried out to characterise ferric hydroxide gel, natural and synthetic goethite and humic acid gel. (author)

[en] A simple, effective and accurate method of decomposition, dissolution and separation for the spectro-photometric determination of Nb and Ta in Nb- Ta and tin slag samples is described. Nb-Ta samples are fused with (1:1) mixture of sodium di- hydrogen ortho-phosphate and tetra sodium pyrophosphate in a Pt crucible. The melt is dissolved in distilled water. Tin slag samples are treated with HF + HNO₃ to remove Si and then evaporated with HNO₃ and fumed with H₂SO₄ to remove HF and HNO₃ completely. Acid hydrolysis was carried out in presence of SO₂ solution. Nb and Ta are precipitated quantitatively from HCl solution. The precipitate is filtered, dried and again fused with the same flux and dissolved in distilled water to get a clear solution. Suitable aliquots are taken for the analysis of Nb by H₂O₂ and Ta by malachite green method. Iron interferes in the analysis of Nb by H₂O₂ method. Hence the optimum parameters for quantitative precipitation of Nb and Ta and complete removal of Fe like volume of sample solution, HCl concentration and effect of SO₂ water are investigated. The validity of the method is checked with CRMs IGS-33, IGS-34 and synthetic mixtures of varied composition conforming to Nb- Ta and Sn slag. For tin slag samples validity of results were checked by comparing with ICP AES analysis without separation. The RSD of the method varies between 1-5% depending on the concentration. (author)

[en] Middle Proterozoic intracratonic Abujhmar Basin forms the northwestern part of Bastar Craton. Volcanosedimentary sequence of Abujhmar Group unconformably overlies the rocks of Bengpal Group in the southern part, Nandgaon Group in the northern part and Dongargarh Granite in the western part. Lineaments such as Bodhghat (NW-SE), Kotri (NNE-SSW), Raoghat (WNW- ESE), Mundatikra (WNW-ESE) and other faults have played major role for disposition of the rocks in and around Abujhmar Basin. The sediments of Abujhmar Basin derived from basement granites, Bailadila iron ore, Nandgaon sandstones/rhyolites and Dongargarh granites have been deposited in a fluviatile to shallow marine environment with Gundul Formation forming the basal unit. Uranium mineralisation in the Gundul Formation of Abujhmar Group is essentially strata bound type and unconformity proximal type. The Upper Gundul sandstone shows profuse development of secondary uranium mineralisation in the central part of the basin near Kerali and Saragipal, indicating strata bound character of the mineralisation. In the northeastern margin along Bogan- Gundul tract, uranium concentration is observed in the lower units, close to the unconformity. Near Kotri lineament (Waler area), the pyritiferous greyish green arkosic sandstone, immediately overlying the conglomerate, also shows significant uranium anomalies. Although the uranium occurrences at Bogan and Waler are apparently strata bound, the influence of structure and their proximity to the basic sills, dykes, flows and proximal placement to the unconformity are noteworthy. Considering the different favourability criteria and wide spread occurrence of uranium anomalies all over the basin, particularly along the margins, in addition to the strata bound sandstone type, unconformity related type uranium concentration of economic significance could also be expected in Middle Proterozoic Abujhmar basin. (author)

[en] This note presents the first account of uranium occurrence (250 m x 2-3 m ) in conglomerate at the base of Satyavedu Formation of Upper Gondwana sediments of Palar Basin, near Allapakonta and Vembakam, Chittoor district, Andhra Pradesh. Grab samples (n=7) have analysed 38 ppm to 218 ppm eU₃O₈, 32 ppm to 232 ppm U₃O₈ with negligible thorium. Radioactivity in conglomerate is associated with chlorite, zircon and ferruginous material (limonite). (author)

[en] A simple, sensitive and efficient method is developed for the separation of Rare earth elements (REEs) La-Lu, and Y and some trace elements Cd, Co, Cr, Cu, Ni,V, Zn from thorium matrix and their subsequent estimations by ICP-AES. In thorium-rich geological samples, the estimation of REE's by ICP-AES suffers from the spectral interferences due to the presence of excess of Th. In the proposed method, thorium is separated from the matrix by the solvent extraction. To optimize the separation, of REEs and trace elements from Th matrix, synthetic mixture solutions was prepared containing Th, REEs and trace elements maintaining different acidic conditions (1M, 2M, 4M, 6M, 8M and 10M HNO₃ and 2M, 4M, 6M and 8M HCl) and each solution was subjected to solvent extraction. The solvent extraction was carried out using a mixture of di-2-ethylhexyl phosphoric acid (in 30 % Toluene) and 1- pentanol in the ratio of 5:1. The aqueous phase containing the required elements was evaporated to dryness and an acidity of 5% HCl is maintained in final volume. Solutions were analysed by ICP-AES and the quantitative recovery of REEs and trace elements were obtained at 6M HNO₃ acidity. The developed method was applied to the certified standard reference material: IGS-36 and the values obtained were comparable with the certified values. The method was also applied to the real time monazite sample and the recovery was quantitative. Corrections have been applied for the REEs inter-elemental interferences in ICP-AES. (author)

[en] Uranium occurrences along the NE-SW trending lineament of the Malani Igneous Suite (MIS) of Neoproterozoic age are being reported for the first time from Tavidar, Danthewara, Lakhavas areas of Jalore district, Rajasthan. The uranium concentration ranges from 3.5 to 340 ppm U in K-rhyolite and rhyolite agglomerates. (author)

[en] The albite rich pegmatoid leucosomes at Naktu, Son valley, host uranium mineralisation and form a major part of the early proterozoic migmatised arkosoic to psammopelitic sedimentary rocks. These leucosomes occur as repeated, concordant lenses and bands in association with melanosomes, measuring 10 m x 5 m to over 1000 m x 160 m with thickness varying from few centimeters to over 30 m. The migmatites show combination of phlebitic, surretic, opthalmitic, and stromatic structures. The uranium minerals are dispersed mainly within the albite rich leucosomes containing disseminations of recrystallized and unaltered biotite selevages. U₃O₈ values range from 0.012% to 0.20% with traces of ThO₂. The mineralised zone is also locally enriched in Mo, Cu, and Y minerals. Uraninite (mostly euhedral) is the main ore mineral; other radioactive minerals include zircon, and xenotime in association with molybdenite, pyrite chalcopyrite, apatite, and fluorite. (author)