Articles written in Journal of Earth System Science

    • A GIS based hydrogeomorphic approach for identification of site-specific artificial-recharge techniques in the Deccan Volcanic Province

      M N Ravi Shankar G Mohan

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      The Deccan Volcanic Province (DVP) of India, as a whole, faces a severe shortage of water despite receiving a high annual rainfall, this is primarily due to excess runoff and lack of water conservation practices. In this study, an attempt is made to identify zones favourable for the application and adaptation of site-specific artificial-recharge techniques for augmentation of groundwater through a Geographical Information System (GIS) based hydrogeomorphic approach in the Bhatsa and Kalu river basins of Thane district, in western DVP. The criteria adopted for the GIS analysis were based on the hydrogeomorphological characteristics of both basins extracted from the IRS-1C LISS-III data supported by information on drainage pattern, DEM derived slope, lineament density, drainage density, and groundwater condition. The integrated study helps design a suitable groundwater management plan for a basaltic terrain.

    • New paleomagnetic results on ~2367 Ma Dharwar giant dyke swarm, Dharwar craton, southern India: implications for Paleoproterozoic continental reconstruction

      N Ramesh Babu M Venkateshwarlu Ravi Shankar E Nagaraju V Parashuramulu

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      Here we report new paleomagnetic results and precise paleopole position of the extensional study on ~ 2367 Ma mafic giant radiating dyke swarm in the Dharwar craton, southern India. We have sampled 29 sites on 12 dykes from NE–SW Karimnagar–Hyderabad dykes and Dhone–Gooty sector dykes, eastern Dharwar craton to provide unambiguous paleomagnetism evidence on the spectacular radiating dyke swarm and thereby strengthening the presence of single magmatic event at ~ 2367 Ma. A total of 158 samples were subjected to detailed alternating field and thermal demagnetization techniques and the results are presented here along with previously reported data on the same dyke swarm. The remanent magnetic directions are showing two components, viz., seven sites representing four dykes show component (A) with mean declination of 94◦ and mean inclination of −70◦ (k = 87, α95 = 10◦) and corresponding paleopole at 16◦N, 41◦E (dp = 15◦ and dm = 17◦) and 22 sites representing 8 dykes yielded a component (B) with mean declination of 41◦ and mean inclination of −21◦ (k = 41, α95 = 9◦) with a paleopole at 41◦N, 200◦E (dp = 5◦ and dm = 10◦). Component (A) results are similar to the previously reported directions from the ~ 2367 Ma dyke swarm, which have been confirmed fairly reliably to be of primary origin. The component (B) directions appear to be strongly overprinted by the 2080 Ma event. The grand mean for the primary component (A) combined with earlier reported studies gives mean declination of 97◦ and mean inclination of −79◦ (k = 55, α95 = 3◦) with a paleopole at 15◦N, 57◦E (dp = 5◦, dm = 6◦). Paleogeographical position for the Dharwar craton at ~ 2367 Ma suggests that there may be a chance to possible spatial link between Dharwar dykes of Dharwar craton (India), Widgemooltha and Erayinia dykes of Yilgarn craton (Australia), Sebanga Poort Dykes of Zimbabwe craton (Africa) and Karelian dykes of Kola-Karelia craton (Baltica Shield).

    • Geochemistry and petrogenesis of tholeiitic dykes from the Chotanagpur Gneissic Complex, eastern India


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      In this study, we present the geochemical analysis on 14 samples from seven distinct E–W trending mafic dykes from the Chotanagpur Gneissic Complex. These dykes have not been studied previously and highlight the importance of igneous and tectonic processes in the Chotanagpur Gneissic Complex. The dykes, in terms of modal mineralogy, do not show notable variations, but textural variations are well noticed. These dykes are characterised as basalt and basaltic andesite (SiO$_{2}$ = 45.48–54.03 wt.%; Mg# = 21–68.5), and comparable with E-MORB type tholeiitic magma series. The dykes are classified into two groups, low Mg# and high Mg# dykes, based on their Mg# and silica content. The major fractionating mineral phases are olivine, plagioclase, and pyroxene. The dykes are variably contaminated with crustal input, as shown by Nb/U vs. (Th/Nb)PM, Th/Nb vs. La/Nb, and Th/Yb vs. Nb/Yb. The dykes also underwent post-magmatic hydrothermal alteration after their emplacement. Semi-quantitative trace element modelling suggests that these dykes are derived by partial melting within spinel peridotite-rich mantle and spinel–garnet peridotite-rich mantle source in the transition zone. The low Mg# dykes are consistent with 3–15% partial melting curves, whereas high Mg# dykes are comparable with 15% melting curve. Finally, we present a conceptual and simplified model for the E–W trending mafic dykes of the CGC, based on the geochemical data of the present study and the available information.

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