Atomic Minerals Directorate for Exploration and Research

Bangalore, India

Atomic Minerals Directorate for Exploration and Research

Bangalore, India
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Kumar A.,Atomic Minerals Directorate for Exploration and Research | Venkatesh A.S.,Indian School of Mines | Kumar P.,Atomic Minerals Directorate for Exploration and Research | Rai A.K.,Atomic Minerals Directorate for Exploration and Research | Parihar P.S.,Atomic Minerals Directorate for Exploration and Research
Ore Geology Reviews | Year: 2017

Lenses of radioactive Quartz Pebble Conglomerates (QPC) and associated quartzites are exposed along western margin of Archean Bonai Granite in Singhbhum-Orissa Craton, eastern India intermittently spreading over a strike length of 8–10 km. QPCs are radioactive while quartzites are mostly non-radioactive in nature. The purpose of the research is to investigate and characterize the radioactive QPC and quartzites geochemically to decipher their paleo-weathering conditions, provenance characteristics and possible tectonic setting of deposition. Geochemical data suggest moderate to high chemical weathering conditions in the provenance areas of QPC and quartzites. Major, trace and REE data indicate predominantly felsic to partly mafic-ultramafic sources for the deposition of radioactive Quartz Pebble Conglomerates from the surrounding Archean terrain. Elevated values of Th, U, Pb, La, Ce, Y and low Sc with high critical trace elemental ratios of Th/Sc, La/Sc, Th/Cr and Zr/Sc in radioactive QPC indicate their derivation from felsic igneous source. Low concentration of Th and Sc in quartzites compared to QPC and their variable Th/Sc ratios indicate both felsic and mafic sources for quartzites, albeit their preferential felsic affiliation. Higher Cr/Th ratios in quartzites (18.4), moderate Cr/Th in QPC (5.42), low to moderate Y/Ni in QPC (0.36–12.4) and quartzite (0.29–1.88), along with Au ranging from 30 to 1527 ppb, Pt up to 188 ppb and 682 ppb in QPC and quartzites respectively point towards some contribution from mafic-ultramafic source as well. REE patterns and in particular negative Eu anomalies for both QPC and quartzites further support their derivation from felsic rocks and could possibly linked to some of the phases of Archean Singhbhum Granite and Bonai Granite. Granitic to pegmatitic source for QPC is also revealed by the presence of rounded to sub-rounded monazite, zircon and thorian-uraninite grains in their matrix. Study indicates that QPC and quartzites were deposited in a passive margin tectonic setting developed during Archean between a span of 3.3 and 3.16 Ga along the western margin of Bonai Granite when the reducing condition was prevalent as indicated by their low Th/U ratios (<4.0) and presence of detrital grains of uraninite and pyrite in QPC. Radioactive QPC from western margin of Archean Singhbhum-Orissa Craton bears broad resemblance with QPC from Witwatersrand basin of South Africa and Elliot Lake, Canada and thus appears to be ideal sites for exploring QPC hosted U (+Au-PGE) mineralization in the analogous areas. © 2017

Ozha M.K.,Indian Institute of Technology Kharagpur | Pal D.C.,Jadavpur University | Mishra B.,Indian Institute of Technology Kharagpur | Desapati T.,Atomic Minerals Directorate for Exploration and Research | Shaji T.S.,Atomic Minerals Directorate for Exploration and Research
Ore Geology Reviews | Year: 2017

In the Samarkiya area, located at the central part of the Aravalli-Delhi Fold Belt (ADFB), uranium mineralization is hosted both by the basement Mangalwar Complex and the overlying supracrustal rocks of the Pur-Banera belt. The present study aims to appraise the geochemical and temporal evolution of uranium mineralization from the basement and the adjoining supracrustals in the Samarkiya area integrating textural features, geochemistry, and in situ U-Th-PbTotal dating of uraninite. Uraninite occurs as inclusions in the major rock forming minerals, viz. plagioclase, quartz, biotite, and chlorite. Based on the shape, location in the host mineral (well inside/at the grain boundary/along or connected to micro-cracks etc.) and association with other secondary uranium minerals, uraninites are classified into different groups, which are compositionally distinct, barring some exceptions. Integrating texture, geochemistry and in situ electron probe dating we propose that in addition to an old event at ∼1.88 Ga in the basement rocks, there are two major events of uraninite formation at ∼1.24–1.20 Ga and ∼1.01–0.96 Ga in both the basement and supracrustal rocks. Although none of the pristine, unaltered uraninites that formed during the above mentioned events contain significant intrinsic minor or rare earth elements, the basement uraninites are consistently much enriched in thorium compared to those from the supracrustal. Based on the compositions, we propose that the basement uraninites formed from a high temperature magmatic/metamorphic fluid, whereas those in the supracrustal rocks crystallized from a low temperature, presumably oxidized fluid. Back-scattered electron images, X-ray elemental mapping of selected elements and EPMA spot analysis of large uraninite grains (both from the basement and the supracrustals) collectively demonstrate that subsequent to the major mineralizing event at ∼1.24–1.20 Ga, the mineralized rocks were subjected to fluid-mediated alteration, which resulted in ∑REE + Y- and Si (Ca)-enrichment of existing ∼1.24–1.20 Ga uraninites in the basement and supracrustal rocks, respectively. We cannot constrain the exact timing of this alteration event. However, as this event altered the ∼1.24–1.20 Ga uraninites and as spot ages of the altered grains yield ages largely between ∼1.24 and 0.96 Ga, it is reasonable to place this event between the second and third stages of uranium mineralization/mobilization at ∼1.20 Ga and ∼1.01 Ga, respectively. The last event that took place at ∼1.01–0.96 Ga most likely represent an episode of recrystallization/alteration of existing uraninite leading to complete Pb-loss and resetting of the isotopic clock. However, we do not entirely reject the possibility of neo-mineralization. The discrete events deciphered from uraninite in the Samarkiya area can also be broadly linked to some major magmatic-metamorphic events, identified from other independent studies, in the ADFB. For example, the earliest ∼1.88 Ga event displayed by basement uraninite is most likely related to a pervasive magmatic-metamorphic event (∼1.86–1.82 Ga) that affected the basement, whereas the last/latest event ∼1.01–0.96 Ga can be linked to a pervasive metamorphic event that affected perhaps the entire ADFB. This last episode can also be linked to the tectono-thermal event related to the Rodinian amalgamation. The ∼1.24–1.20 Ga event appears to be somewhat enigmatic in the context of well-known geological events in the area. However, based on some very recently published data, we interpret this to be a post-peak metamorphic (∼1.37–1.35 Ga) hydrothermal event or even a new metamorphic event, hitherto unknown. © 2017 Elsevier B.V.

Sinha K.K.,Atomic Minerals Directorate for Exploration and Research | Pandey P.,Atomic Minerals Directorate for Exploration and Research | Bhairam C.L.,Atomic Minerals Directorate for Exploration and Research | Parihar P.S.,AMD Inc
Journal of the Geological Society of India | Year: 2011

In the western part of Bundelkhand massif, a caldera with intra-caldera sediments, known as Dhala Formation, occurs as an outlier in and around Mohar village of Shivpuri district, Madhya Pradesh. For the first time, occurrence of peperite is being reported from the basal part of the Dhala sediment. Two types of peperites have been recognized: blocky and fluidal or globular with variable morphology. In peperitic zones, features like soft sediment deformations, presence of sediment into the rhyolite along cracks, vesiculation of the sediments and other evidences suggestive of sediment fluidization are some definite characteristics of interaction of hot magma with wet sediments forming peperite. The occurrence of peperites reflects the contemporaniety of deposition of the Dhala sediments and volcanism, which is well in accordance to the volcanic origin of Dhala structure. Further, the nature of unconformity between the Dhala and overlying Kaimur which is characterized by merely a few centimeter thick pebbly/conglomeratic bed does not appear to represent a large hiatus as expected between the Semri and Kaimur of Vindhyan Supergroup. So, the contemporaniety of the Dhala Formation (at least the lower part) as reflected by occurrence of peperites, coupled with the available age of the rhyolite and the nature of the unconformity between the Dhala and overlying Kaimur provide convincing evidence to correlate the Dhala Formation with the Lower part of the Kaimur and unlikely with the Semri Group or Bijawar as proposed earlier. © 2011 Geological Society of India.

Bhattacharya D.,Atomic Minerals Directorate for Exploration and Research | Joshi G.B.,Atomic Minerals Directorate for Exploration and Research | Sharma R.,Atomic Minerals Directorate for Exploration and Research
Journal of the Geological Society of India | Year: 2011

Several small lensoidal bodies of felsic volcanics are exposed in a curvilinear pattern within the brecciated granitoids of Bundelkhand Gneissic Complex (BGC) at Mohar. Sub-surface data reveals extensive presence of these felsic volcanics below the sediment of Vindhyan Supergroup. It occurs like a sheet with thickness varying from 12 m to 134 m. Its lateral extent has been traced upto 4.8 km. Multiple flows of felsic magma are identified based on colour, granularity, cross cutting relations and cyclic distribution of multiple vesicular bands along the entire thickness of felsic magma. The felsic rock contains upto 13.21% K2O. Chemical composition of these felsic volcanics varies across the column. Petrographically and chemically all these felsic volcanics are identified as rhyolite or rhyolite tuff. Significant uranium mineralisation of 0.0165% eU3O8 average grade has been intercepted for 11.10 m thick with <0.005% ThO2 within the felsic rock. Radiometric assay of a mineralised intercept (15 cm length) has revealed up to 0.15% U3O8 with disequilibrium in favour of parent. Uranium occurs as disseminated grains of coffinite - (Y) associated with pyrite, chalcopyrite, galena, molybdenite, hematite, fluorite, anglesite and cerrusite. Mineral assemblage and mode of occurrence of the uranium and other minerals in the host rock indicates its hydrothermal nature. This is the first reported uranium occurrence from the volcanogenic environment of Bundelkhand. © 2011 Geological Society of India.

Cyriac B.,Atomic Minerals Directorate for exploration and Research | Balaji B.K.,Atomic Minerals Directorate for exploration and Research
Microchimica Acta | Year: 2010

A novel, single-step route has been developed for the synthesis of solid phase adsorbent silica modified with xylenol orange. The addition of cationic surfactant cetyl tri-methylammonium bromide during the synthesis of the adsorbent supports the formation of a stable coating of xylenol orange on silica. The adsorbent showed no signs of degradation in contact with organic solvents and with solutions of varying pH between 1 and 9. This adsorbent has been used for separation and pre-concentration of uranium from hydro-geochemical samples with high calcium content and from sea water. Quantitative sorption of uranium was observed above pH 3 and complete desorption can be achieved using 0.2 M sodium pyrophosphate solution. The uranium content in the extract was determined by laser fluorimetric technique. The equilibration time is 30 min. The sorption capacity of the adsorbent for uranium is 10 mg g -1. An enrichment factor of 50 was obtained by this procedure taking 500 mL of sample solution. Uranium concentrations down to 0.05 ng mL -1 can be determined after pre-concentration using this method. The relative standard deviation at an 0.1 ng mL -1 level is ±15%. © 2010 Springer-Verlag.

Dey S.,Indian School of Mines | Pandey U.K.,Atomic Minerals Directorate for Exploration and Research | Rai A.K.,Atomic Minerals Directorate for Exploration and Research | Chaki A.,Atomic Minerals Directorate for Exploration and Research
Journal of Asian Earth Sciences | Year: 2012

Geochemical and Nd isotope data on granitoids of the NW part of the late Archaean eastern Dharwar craton are presented to elucidate their petrogenesis and role in crust formation. The granitoids are divided into three suites viz. trondhjemite-granodiorite gneisses, biotite monzogranites and porphyritic biotite granodiorites. The gneisses are pre- to syn-kinematic (with respect to deformation in the adjacent Hungund-Kushtagi schist belt), which show variable SiO 2 and Al 2O 3, enriched LREE and depleted HREE with slightly negative to no Eu anomalies. They display unusual chemistry in having higher FeO(T), K 2O, Ba, Cr and Ni compared to the typical Archaean tonalite-trondhjemite-granodiorite (TTG). The biotite monzogranites are mostly syn- to late-kinematic and exhibit evolved calc-alkaline compositions with high SiO 2, K 2O, LILE and LREE, depleted to undepleted HREE and strongly negative to no Eu anomalies. The porphyritic granodiorites show syn- to late-kinematic calc-alkaline, sanukitoid-like character with a wide range of SiO 2, higher TiO 2, P 2O 5, Sr, Ba, Cr and Ni, and lower Rb. They, however, uniquely display higher K 2O, ΣREE and Th than typical sanukitoids. The trondhjemite-granodiorite gneisses are interpreted as product of melting of a subducted basaltic slab followed by slight contamination from the overlying metasomatized mantle wedge. Subsequent melting of the extremely metasomatized mantle wedge resulted in formation of the parental magma of the porphyritic granodiorites. Intrusion of the latter triggered melting of the TTG crust accreted earlier and generated the evolved monzogranites. The monzogranites occurring east of the Hungund-Kushtagi schist belt show higher εNd but lower T DM ages than those occurring to the west, indicating that terranes with different histories were juxtaposed by lateral accretion. © 2011 Elsevier Ltd.

Basu H.,Atomic Minerals Directorate for Exploration and Research | Sastry R.S.,Osmania University | Achar K.K.,Atomic Minerals Directorate for Exploration and Research | Umamaheswar K.,Atomic Minerals Directorate for Exploration and Research | Parihar P.S.,Atomic Minerals Directorate for Exploration and Research
Precambrian Research | Year: 2014

An analysis of facies was done to understand the depositional environment and the palaeoclimate of the sedimentary succession from the lower part of the Palaeoproterozoic (~2.0. Ga) Gulcheru Formation exposed along the southwestern margin of the Cuddapah Basin. Twelve distinct sedimentary facies were identified and grouped into three main facies associations - wadi fan, ephemeral fluvial and aeolian. Identification of the fluvial and the aeolian facies allowed a more elaborate interpretation of the depositional environment and its palaeoclimate. Facies characteristics indicated that the sediments in the beginning were deposited in a dominantly aeolian realm, under warm and semiarid climatic condition. Translatent strata, pin stripe lamination, zibars, high-index granule ripples, sand sheet deposits, grainflow cross-strata and grainfall laminae, asymptotically down-lapping cross-strata often with erosional lower bounding surface and massive sand-bodies with bimodal fabric, the unambiguous evidences of aeolian depositional regime led to this conclusion. However, the aeolian regime was often punctuated temporarily by fluvial input from ephemeral streams during sudden rainstorm. Depending upon the size, character and availability of sediments, relief difference and the sediment/water ratio cohesionless debris flow, hyperconcentrated flood flow and sheetflood deposits were formed near the basin margin, whereas, coarse-load braided channel deposits were laid further inside the basin. Ephemeral lakes/ponds were formed due to stagnation of floodwater in normally dry interdune lows. Overbank-interdune sediments were deposited in those ephemeral lakes/ponds. Amongst the aeolian facies, translatent strata and sand sheet dominate in the west, whereas, massive beds and dunes with well-developed slipfaces dominate in the eastern part. The spatial distribution of the aeolian bedforms suggests development of erg apron to the west and dune field (erg) to the east. The aeolian sediments identified in the Gulcheru Formation may be considered to be amongst the oldest Palaeoproterozoic aeolian sediments of the world. © 2014 Elsevier B.V.

Tripathy S.,Indian Institute of Technology Bhubaneswar | Bhattacharyya P.,Indian Statistical Institute | Mohapatra R.,Minnesota State University, Mankato | Som A.,Atomic Minerals Directorate for Exploration and Research | Chowdhury D.,Indian Institute of Technology Kharagpur
Ecological Engineering | Year: 2014

The ratios of microbial parameters/organic carbon indicated that inhibition of microbial growth. The study was carried out on an municipal solid waste dumping site, more than hundred year old, located on the outskirts of Kolkata metropolitan city in India to determine the concentrations of different forms of selected metals (Zn, Cu, Pb, Cr, and Ni), their effect on microbial ecophysiological parameters (microbial biomass, microbial metabolic quotient, microbial respiration quotient), fluorescein diacetate hydrolyzing activity and enzyme activities in solid waste amended soils. A sequential extraction technique was used to quantify water soluble, exchangeable, carbonate bound, Fe/Mn oxide bound, organic bound, and residual fractions of metals. Metal concentrations in the two most labile fractions (i.e. water soluble and exchangeable fractions) were generally low. The concentrations of different forms of metals, microbial ecophysiological parameters and enzyme activities were found to be significantly higher in solid waste amended soils compared to the normal background soil around the study area. Significant positive correlations were observed between the microbial parameters and organic carbon content of the waste amended soil. The contents of microbial biomass C, fluorescein diacetate and enzyme activities did not necessarily decrease with increasing heavy metal content, reflecting the importance of other environmental factors, e.g. differences in organic C content. The ratios of different microbial parameters with organic C were significantly negatively correlated with metal concentrations while inhibition increased with increased bioavailability of metals. Although the waste amended soils had significantly higher microbial biomass and activities than the background soil, due to higher organic matter content, the ratios of microbial parameters/organic carbon indicated that inhibition of microbial growth and activities had occurred due to metal stress. This indicates that the use of municipal solid wastes in agriculture would lead to destruction of soil quality in the long run. © 2014 Elsevier B.V..

Kukreti B.M.,Bhabha Atomic Research Center | Kumar P.,AMD Inc | Sharma G.K.,Atomic Minerals Directorate for Exploration and Research
Applied Radiation and Isotopes | Year: 2015

Exploratory drilling was undertaken in the Lostoin block, West Khasi Hills district of Meghalaya based on the geological extension to the major uranium deposit in the basin. Gamma ray logging of drilled boreholes shows considerable subsurface mineralization in the block. However, environmental and exploration related challenges such as climatic, logistic, limited core drilling and poor core recovery etc. in the block severely restricted the study of uranium exploration related index parameters for the block with a high degree confidence. The present study examines these exploration related challenges and develops an integrated approach using representative sampling of reconnoitory boreholes in the block. Experimental findings validate a similar geochemically coherent nature of radio elements (K, Ra and Th) in the Lostoin block uranium hosting environment with respect to the known block of Mahadek basin and uranium enrichment is confirmed by the lower U to Th correlation index (0.268) of hosting environment.A mineralized zone investigation in the block shows parent (refers to the actual parent uranium concentration at a location and not a secondary concentration such as the daughter elements which produce the signal from a total gamma ray measurement) favoring uranium mineralization. The confidence parameters generated under the present study have implications for the assessment of the inferred category of uranium ore in the block and setting up a road map for the systematic exploration of large uranium potential occurring over extended areas in the basin amid prevailing environmental and exploratory impediments. © 2015 Elsevier Ltd.

Maithani P.B.,Atomic Minerals Directorate for Exploration and Research | Srinivasan S.,Atomic Minerals Directorate for Exploration and Research
Energy Procedia | Year: 2011

Felsic volcanics constitute a primary source of uranium for forming an economic deposit. All over the world, volcanic rocks have not received due attention they deserve in uranium exploration. The volcanogenic deposits have been grouped with "other deposits", as they constitute a meager <0.5% of world uranium resources. Exploration inputs in the western world have identified a number of uranium deposits associated with volcanic rocks. The uranium resources contributed by volcanic type deposits all over the world stand at 3, 62, 000 te U3O8 (IAEA 2008 Compilation). The significance of acid volcanic rocks as a potential uranium source lies in the readily leachable form of their uranium content. A detailed study carried out in Australia to understand the spatial and temporal relationsh ip between the uranium deposits and the unmineralized, uranium enriched rocks from across the continent clearly indicated the role of the acidic volcanics as a potential provenance. Among the acid volcanics, rhyolites form an ideal source followed by welde d tuffs, ignimbrites, etc. The alkali or topaz rhyolite is ideal for its enrichment in many lithophile elements including uranium, which are amenable to subsequent leaching by meteoric water. In India the uranium exploration activities in the early 50s till the 90s were mainly confined to the Singhbhum Shear Zones, the Himalayas, Meghalaya plateau, parts of Central India and the geological environs of the Dharwar Craton. The granitic rocks, especially the peraluminous biotite - granite was always considered as a potential source for uranium and the geological environs closer to these granites always remained the first order targets. A number of small to medium size uranium deposits have been identified in Singhbhum Shear Zone, parts of Cuddappah, Bhima Basins and in Meghalaya. Now since the significance of the volcanic rocks, especially the felsic volcanics as a potential source of uranium has been clearly understood, it is imperative to reorient our exploration strategy to tap the potential of these volcanic rocks. The Malani Magmatic Province (MMP) in the northwestern part is the largest suite of an-orogenic acid volcanics in India occupying an area of 50000 sqkm. The Proterozoic Basins of India are replete with volcanic activity, mainly acid volcanism. In the southern and Central India, Dharwar and parts of Central Indian Craton also witnessed significant acidic igneous activities. The Cuddapah and the Vindhyan Basins have also recorded extensive acidic volcanic activity in the Papaghni, Chitrvati, Nallamalai Groups and Semri and Kaimur Groups respectively. In view of this the Proterozoic Basins mentioned above and the geological environs adjacent to the MMP deserve a re -look to have a proper assessment of their uranium potential, using integrated exploration inputs. © 2011 Published by Elsevie Ltd.

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