Articles written in Journal of Earth System Science

    • Carbonate hosted intermetallic compounds in Paleoproterozoic Salumber Ghatol metallogenic belt, Aravalli Craton, Rajasthan, India


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      Carbonate hosted intermetallic compound in the Umarvaniyan area is localized within the intensively sheared (mylonitised) dolomite in a NW–SE shear zone ($\sim$15 km), belongs to Salumber Ghatol metallogenic belt, in Debari Group of Aravalli Craton, Rajasthan, India. It is characterized by extensive silicification and ferruginisation with hematite, goethite, magnetite and native gold specks. The intermetallic compound within the dolomite is composed of varying proportion of Cu–Zn–Ni–Os–Fe which has been detected by electron probe microanalysis (EPMA) study. The EMPA (WDS) results of the intermetallic compounds also reveal occurrences of intermetallic compounds of Cu–Zn–Ni–Os–Fe and native Au. The occurrence of these non-separable compounds is probably because these metals were formed at very high temperatures and in reducing condition during the evolving shear with low oxygen and low sulfur fugacity. The fast cooling effect thereafter probably made the geochemical environment least conducive for reaction between Cu/Zn/Ni and sulphur or oxygen.

    • Tungsten mineralized Neoproterozoic Degana Peraluminous Granite around Rewat Hill, Rajasthan, NW India: Implications from sub-surface data and geochemistry


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      The present study emphasises occurrence, mineral assemblages and mineral chemistry of the Neoproterozoic Degana Peraluminous Granite (DPG) around Rewat Hill and its fertility. Based on field evidences and nature of occurrences of wolframite, the tungsten mineralization of the Rewat Hill has been classified into five types; Type-I: quartz–wolframite vein, Type-II: quartz–muscovite–wolframite–polymetallic sulphide vein, Type-III: DPG hosted wolframite, Type-IV: stock-works hosted wolframite in phyllite and Type-V: gravel bed hosted wolframite. Tungsten mineralization in DPG was established in the exposed part by various workers but extension of fertile DPG and its potentiality for tungsten and associated mineralization in the soil-covered area around Rewat Hill remained unexplored. In this study, sub-surface exploration through vertical and inclined boreholes studies has been established which suggest a possible extension of fertile DPG, i.e., Type-I and Type-III tungsten mineralization in soil cover. Tungsten concentration in fertile DPG under soil cover ranges between 402.98 and 5025.45 ppm with higher LREE (58.36–288.67 ppm) and relatively lower HREE (14.64–92.48 ppm). Sub-surface data and geochemistry reveal that soil covered northern and northwestern parts around Rewat Hill of the Degana area is the future potential for tungsten mineralization.

    • Geochemistry and economic potential of tourmalinites from Salumber–Ghatol Metallogenic Belt, southeastern Rajasthan, India


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      The Salumber–Ghatol Metallogenic Belt (SGMB) in southeastern Rajasthan forms a part of volcanosedimentary sequence of Debari Group, Aravalli Supergroup and hosts several copper-gold prospects. Tourmalinites in the Mahuri Khera area of SGMB are exposed in the form of 30–40 cm thick dark grey black bands that can be traced discontinuously for about 1 km along strike present at the contact of schist and marble and also within the marble. The chemical similarity of tourmalinite and schist with high Fe/ Al ratio, higher ${\sigma}$REE and LREE/HREE ratio, and negative Eu anomaly as well as the similar Fe/Al,Mg/Al and Na/Al molar ratios suggest that the tourmalinite from SGMB are formed by the replacement of clastic sediments with little input from exhalative Cuids. It is further inferred that the local clastic metasediments provided the necessary Fe, Mg and Na for the formation of tourmalinite. The average W concentration in the bulk rock samples of tourmalinite is 380 ppm with some samples showing W values above 1000 ppm. The higher values of W are supported by the presence of small grains (10–50 micron) of scheelite in the tourmalinite. Anomalous values for tungsten along with scheelite disseminations from these tourmalinites make this area an interesting tungsten prospect.

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