Precambrian deformed granites of possible basement in the Himalayas |
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| Institution: | 1. Applied Isotope Research Group, Departamento de Geologia, Escola de Minas, Universidade Federal de Ouro Preto, Ouro Preto, MG 35400-000, Brazil;2. School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK;1. Department of Earth Sciences, Manipur University, Imphal 795003, India;2. Institute of Geosciences, Mineralogy, J.W. Goethe University, Frankfurt 60438, Germany;3. Physical Research Laboratory, Navrangpura, Ahmedabad 380009, India;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education, and College of Marine Geosciences, Ocean University of China, Qingdao 266100, China;3. Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China;4. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;5. Institute of Geology, China Earthquake Administration, Beijing 100029, China;6. Beijing SHRIMP Centre, Chinese Academy of Geological Sciences, Beijing 100037, China;1. Laboratoire GET, University of Toulouse, IRD, CNRS UMR 5563, Observatoire Midi-Pyrénées, 14 Ave. Edouard Belin, 31400 Toulouse, France;2. IFAN Cheikh Anta Diop, Dakar, Senegal;3. Institute of Geology and Paleontology, Charles University in Prague, Albertov 6, 12843 Praha 2, Czech Republic;4. Czech Geological Survey, Klárov 3, 11821 Praha 1, Czech Republic;5. Centre for Exploration Targeting, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;6. Département de Géologie, Université de Ouagadougou, Burkina Faso;7. Volta Resources Inc., Currently B2Gold Corp., Vancouver, Canada |
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| Abstract: | Granitic rocks are abundant in the Axial zone, the core of the Himalayas. The Lesser Himalayan unfossiliferous metasedimentary sequence lying to the south of the Axial zone also contains concordant sheets of granitic rocks which were earlier described either as intrusive or metamorphosed volcaniclastic sediments. These granites have yielded Precambrian radiometric ages.The Lesser Himalayan deformed granites have been demarcated and we suggest that they represent thrust wedges of the Precambrian (older than 1000 Ma) basement rocks of the Himalayas. The deformed granite sheets of the Eastern Himalayas show the development of various types of mylonite. The chemical characters of these granites vary within reasonable limits. Geochemistry and Sr isotope ratios suggest their derivation by melting from crustal material and sediments, probably greywacke, to variable degrees. From geochemical evidence it is suggested that the central crystalline rocks of the Axial zone may contain reworked Precambrian basement components. The studied granites provide evidence of a Precambrian metamorphic and anatectic event in the Himalayas. |
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