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Pal D.C.,Jadavpur University | Sarkar S.,Jadavpur University | Mishra B.,Indian Institute of Technology Kharagpur | Sarangi A.K.,Uranium Corporation of India Ltd
Journal of Earth System Science | Year: 2011

The Jaduguda U (-Cu-Fe) deposit in the Singhbhum shear zone has been the most productive uranium deposit in India. Pyrite occurs as disseminated grains or in sulphide stringers and veins in the ore zone. Veins, both concordant and discordant to the pervasive foliation, are mineralogically either simple comprising pyrite ± chalcopyrite or complex comprising pyrite + chalcopyrite + pentlandite + millerite. Nickel-sulphide minerals, though fairly common in concordant veins, are very rare in the discordant veins. Pyrite in Ni-sulphide association is commonly replaced by pentlandite at the grain boundary or along micro-cracks. Based on concentrations of Co and Ni, pyrite is classified as: type-A - high Co (up to 30800 ppm), no/low Ni; type-B - moderate Co (up to 16500 ppm) and moderate to high Ni (up to 32700 ppm); type- C - no/low Co and high Ni (up to 43000 ppm); type-D - neither Co nor Ni. Textural and compositional data of pyrites suggest that the hydrothermal fluid responsible for pre-/early-shearing mineralization evolved from Co-rich to Ni-rich and the late-/post-shearing fluid was largely depleted in minor elements. Sulphur isotope compositions of pyrite mostly furnish positive values ranging between -0.33 and 12.06‰ Composite samples of pyrites with only type-A compositions and mixed samples of type-A and type-B are consistently positive. However, pyrite with mixed type-A and type-C and pyrite with type-D compositions have negative values but close to 0‰ By integrating minor element and sulphur isotope compositions of pyrite in conjunction with other published data on the Jaduguda deposit, it is proposed that reduced sulphur for the precipitation of most pyrites (type-A, type-B) was likely derived from isotopically heavy modified seawater. However, some later sulphur might be magmatic in origin remobilized from existing sulphides in the mafic volcanic rocks in the shear zone. © Indian Academy of Sciences.

Maurya V.P.,Indian School of Mines | Bhattacharya B.B.,se National Center For Basic Science | Adhikari P.K.,Uranium Corporation of India Ltd | Das L.K.,New Garia Co operative Housing Society
Journal of Applied Geophysics | Year: 2015

The regional magnetotelluric (MT) survey across Dalma Volcanics (DVs) in North Singhbhum Mobile Belt (NSMB) was carried out to obtain the conductivity model and to understand the metallogeny. The structure in general is 2-D and the average strike is N60°W. 2-D inversions using TE + TM and TE + TM + Tzy were carried out. Both inversions derived models with similar features but with modified shape. The TE + TM + Tzy inversion brings up two conducting zones enveloping three anomalous conducting bodies. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis of the samples collected from 8 to 10. m pit from different stratigraphic units of Dalma volcano-sedimentary belt indicates the presence of gold, silver, uranium and copper. The study area is a felsic dominated rifted margin and shows high conductivity contrast along with high gravity, magnetic and significant radiometric anomaly. Thus, the conducting zones indicate the presence of volcanogenic massive sulfide (VMS) or volcano hosted gold deposit (Au-VMS) in NSMB. © 2015 Published by Elsevier B.V.

Panigrahi D.C.,Indian School of Mines | Mishra D.P.,Indian School of Mines | Sahu P.,Indian School of Mines | Bhowmik S.C.,Uranium Corporation of India Ltd
Annals of Nuclear Energy | Year: 2015

Monitoring of radiological parameters in underground uranium mines is essential to maintain the radiation levels within safe limits. In this study, the radiological parameters such as external gamma emitted from ore body, long-lived alpha activity associated with ore dust and radon concentration in an operating underground uranium mine located at Jaduguda, India were measured using different equipments such as micro-R radiation survey meter, personal air sampler and scintillation cell. The geometric mean values of external gamma radiation level, long-lived alpha activity, radon activity concentration and equilibrium equivalent radon (EER) concentration were found to be 2.39 μGy h-1, 16.84 mBq m-3, 872.89 Bq m-3 and 436.44 Bq m-3 respectively with their geometric standard deviations of 1.56, 3.21, 1.58 and 1.58. The total radiation dose received by the miners estimated from the radiological parameters was found to be well below the prescribed limit of 20 mSv y-1 recommended by International Commission on Radiation Protection (ICRP), and hence, it may not pose significant health hazards to the Jaduguda miners. ©2014 Elsevier Ltd. All rights reserved.

Sarangi S.N.,Institute of Physics, Bhubaneswar | Adhikari P.K.,Uranium Corporation of India Ltd | Pandey D.,Banaras Hindu University | Sahu S.N.,Institute of Physics, Bhubaneswar
Journal of Nanoparticle Research | Year: 2010

CdSe nanocrystalline thin films have been synthesized on indium tin oxide (ITO) substrates by an electrodeposition technique. A Schottky junction device in the configuration, ITO/nano-CdSe/Au has been fabricated to study the device interface properties by current (I)-voltage (V) and capacitance (C)-voltage (V) measurements and compared with the ITO/bulk-CdSe/Au device. The I-V characteristics of the nano-CdSe device shows a series resistance effect and C-V characteristics show the presence of surface/interface traps induced by a thin native oxide layer at the nano-CdSe/Au interface and is responsible to the deviation in the ideal Mott-Schottky behavior. The presence of a thin oxide layer on the CdSe nanocrystal surface has been identified from Rutherford backscattering (RBS) spectrometry. The low frequency capacitance response of the nano-CdSe device characteristics are being compared with the bulk device, which confirms the presence of surface/interface states within the band gap of CdSe nanocrystals. Mott-Schottky plots at different frequencies indicate the formation of a Schottky barrier between nano-CdSe and Au junction. © 2009 Springer Science+Business Media B.V.

Pal D.C.,Jadavpur University | Chaudhuri T.,Jadavpur University | McFarlane C.,University of New Brunswick | Mukherjee A.,Jadavpur University | Sarangi A.K.,Uranium Corporation of India Ltd
Economic Geology | Year: 2011

The present study combines textures, compositions, and in situ dating of allanite and whole-rock geochemistry from the Bagjata uranium deposit in the Singhbhum shear zone, the most important uranium-producing belt in India, to investigate the chemical evolution of rare earth element (REE) mineralization. Allanite, volumetrically the most important sink of light rare earth elements (LREEs) in this deposit, occurs as disseminated grains, pockets, veins, and stringers in biotite schist and chlorite schist. Metasomatic addition of LREEs in the rock was associated with Ca-K-Fe ± B metasomatism, as evident from the vein mineralogy. The allanite-bearing metasomatized rocks are locally extremely enriched in REEs, reaching up to ∼4.8 wt percent ∑REEs. The textures and compositions of allanite demonstrate that early REE-rich allanite was replaced by later, relatively less REE bearing allanite-epidote, and this alteration followed a substitution scheme of REE+3 + (Fe +2, Mg+2) → Ca+2 + (Al, Fe+3). The presence of halite-bearing fluid inclusions in associated tourmaline, high Cl content of biotite, and other circumstantial evidence indicate that a high-salinity, Cl-rich fluid was likely responsible for initial LREE metasomatism. A later hydrothermal event altered preexisting allanite and removed REEs. The more oxidized nature of altered allanite and the presence of unidentified secondary REE minerals in association with sulfide might indicate the involvement of oxidized, sulfate-rich fluid in the alteration of allanite and the removal of REEs. Alternatively, fluoride complexing of REEs and selective removal of HREEs during this alteration are possible. In situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating of allanite and monazite indicates that LREE metasomatism took place at ∼1.88 Ga. The next hydrothermal event, which altered existing allanite, removed some REEs, and perhaps was associated with U (+HREE) addition, is dated at ∼1.66 Ga. The youngest age determined from the thin rim of allanite is ∼1.02 Ga. These three different ages, determined from allanite, overlap with the known thermotectonic events in and around the Singhbhum shear zone. Comparison between the calculated ∑REE content of allanite-rich rock prior to allanite alteration and whole-rock ∑REE composition of the same rock suggests that the addition of a large quantity of REEs was followed by significant REE removal. Strong variations in the modal abundances of the constituent minerals and in whole-rock compositions, including REEs, indicate open-system behavior. The whole-rock REE pattern suggests that decoupling between LREEs and HREEs might be possible during superimposed alteration. Therefore, petrogenetic modeling using an REE-based discrimination diagram and REE patterns should be done with caution for rocks that underwent multiple events of hydrothermal fluid flux. © 2011 Society of Economic Geologists, Inc.

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