Tracing hydrothermal mineral thenardite in geysers/hot springs of North-western Himalayan belt,Ladakh Geothermal Province,India by hydrogeochemistry,fluid-mineral equilibria and isotopic studies |
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| Institution: | 1. Geological Survey of India, Northern Region, Lucknow 226024, India;2. Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi, India;3. ONGC Energy Centre, SCOPE Minar, Lakshmi Nagar, Delhi 110092, India;4. Department of Geology, Institute of Science, Banaras Hindu University, Varanasi, India;1. Laboratório de Estudos Tectônicos (LESTE), Universidade Federal dos Vales do Jequitinhonha e Mucuri, Campus JK, MGT 367, Km 583, n° 5000 Alto da Jacuba, Diamantina, MG 39100-000, Brazil;2. Universidade Federal de Ouro Preto, Campus Morro do Cruzeiro, Bauxita, Ouro Preto, MG, 35.400-000. Brazil;1. University of Wrocław, Institute of Geological Sciences, Department of General Hydrogeology, Cybulskiego Street 32, 50-205 Wrocław, Poland;2. University of Wrocław, Institute of Geological Sciences, Department of Applied Geology, Geochemistry and Environment Management, Cybulskiego Street 30, 50-205 Wrocław, Poland;1. Planetary Chemistry Laboratory, Dept. of Earth & Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St Louis, MO 63130, USA;2. Materials and Structures Division, NASA Glenn Research Center/HX5, 21000 Brookpark Road, Cleveland, OH 44135, USA;1. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China;2. Institute of Subsurface Energy Systems, Clausthal University of Technology, Clausthal Zellerfeld 38678, Germany;3. State Key Laboratory of Geohazard Prevention and Geoenvironmental Protection, Chengdu University of Technology, Chengdu 610059, China;4. Department of Petroleum & Gas Engineering, University of Engineering & Technology, 54890 Lahore, Pakistan;5. Sichuan bureau of geology & mineral resources - 402 Team, Chengdu 611743, China;1. Geology & Isotope Geology Division, Geological Survey of India, 15 A & B Kyd Street, Kolkata 700016, India;2. Central Chemical Laboratory, Geological Survey of India, 15 A & B Kyd Street, Kolkata 700016, India |
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| Abstract: | The present study highlights the first evidence of hydrothermal mineral Thenardite (Na2SO4) from Puga geothermal area, North-western Himalayan belt in Ladakh Geothermal Province, India, which is unequivocal evidence for the presence of high-temperature hydrothermal fluid activity from one of the thickest crust areas of the Earth. The Puga geothermal belt illustrates a fault-bounded hydrothermal system with a clearly defined conductive zone, coinciding with Kiagar Tso fault typically exemplifying a shallow-level medium enthalpic geothermal reservoir. The hydrogeochemistry suggests that thermal and non-thermal waters are of Na-Cl-HCO3 and Ca-Mg-HCO3 type, respectively, with neutral to near alkaline pH. The silica and cation geothermometry reveal sub-surface temperatures around 150 °C and 250 °C, respectively, at shallow depth; however, >250 °C is anticipated at the deepest levels (~3 km). Stable isotope (δD and δ18O) studies explicate depletion of isotopic content for thermal waters over Puga river water and radiogenic isotope (3H) suggests matured thermal waters with ongoing water-rock interactions. The recharge altitude estimation and physiographic studies put forth that geothermal reservoir is recharged with the ice masses located at an altitude of 6458 m above mean sea level (msl) in the west of Puga valley, probably from the highest peak of Polokong La mountain. The two key processes participating in regulation of proportions of the dissolved salts in the thermal waters are silicate weathering and ion-exchange kinetics. The powder X-ray diffraction study reveals a major occurrence of hydrothermal mineral thenardite in the hot spring deposits for the first time along with huge encrustations of trona, borax, calcite and elemental sulfur. The high-temperature fluids encounter thenardite, pyrite, and jarosite-bearing minerals in basement rock causing enrichment of SO42− and Cl− in geothermal waters. The temperature-dependent speciation modelling (50 °C–200 °C) for major ion Na+ reveals the composition of the reservoir fluid (~150 °C): Na+ > NaCO3− > NaSO4− > NaHCO3 > NaF > NaOH. A conceptual evolution model of thermal waters involving the recharge-deep circulation-mixing-discharge of thermal springs is hence put forth in the study using various hydrogeochemical insights. |
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