• AMAR AGARWAL

      Articles written in Journal of Earth System Science

    • Back-thrusting in Lesser Himalaya: Evidences from magnetic fabric studies in parts of Almora crystalline zone, Kumaun Lesser Himalaya

      Amar Agarwal K K K K Agarwal R Bali Chandra Prakash Gaurav Joshi

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      The present study aims to understand evolution of the Lesser Himalaya, which consists of (meta) sedimentaryand crystalline rocks. Field studies, microscopic and rock magnetic investigations have beencarried out on the rocks near the South Almora Thrust (SAT) and the North Almora Thrust (NAT),which separates the Almora Crystalline Zone (ACZ) from the Lesser Himalayan sequences (LHS). Theresults show that along the South Almora Thrust, the deformation is persistent; however, near theNAT deformation pattern is complex and implies overprinting of original shear sense by a youngerdeformational event. We attribute this overprinting to late stage back-thrusting along NAT, active afterthe emplacement of ACZ. During this late stage back-thrusting, rocks of the ACZ and LHS were coupled.Back-thrusts originated below the Lesser Himalayan rocks, probably from the Main Boundary Thrust,and propagated across the sedimentary and crystalline rocks. This study provides new results frommultiple investigations, and enhances our understanding of the evolution of the ACZ.

    • Uranium enrichment at North Almora Thrust Zone, Kumaun Lesser Himalaya, Uttarakhand, India

      GAURAV JOSHI K K AGARWAL AMAR AGARWAL J R VIDAL-SOLANO

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      Intensely deformed and mylonitised rocks of the Almora Crystalline Zone (ACZ) have shown the potential of $^{238}U$ and $^{232}Th$ enrichment. $^{232}Th$, $^{238}U$ and $^{40}K$ are investigated by gamma-ray spectrometry in the rock samples collected along the three selected traverses across the North Almora Thrust Zone (NATZ). Obtained average values of U and Th are much higher, 7.3 and 23.9 ppm, respectively, than the average upper crustal abundances (2.8 and 10.7 ppm). The Th/Ra(eU) varies between 2.1 and 23, indicating a higher concentration of Th. The enrichment is due to the remobilisation of the radioisotopes due to the intense mylonitisation and metamorphism from the granitic protolith. The zones of enrichment, although concentrated near NATZ, show a heterogeneous distribution.

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