A novel model for silicon recycling in the lithosphere: Evidence from the Central Asian Orogenic Belt |
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| Institution: | 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China;2. College of Geoscience, China University of Petroleum, Beijing, China;3. Key Laboratory of Tectonics and Petroleum Resources of the Ministry of Education, School of Earth Resources, China University of Geosciences, Wuhan, China;4. Energy & Geoscience Institute, University of Utah, Salt Lake City, UT, USA;5. Unconventional Petroleum Research Institute, China University of Petroleum, Beijing, China;6. Centre for Earth Sciences, Indian Institute of Science, Bangalore, India;7. School of Earth Sciences and Resources, China University of Geosciences Beijing, Beijing 100083, China;8. Department of Earth Sciences, University of Adelaide, SA 50005, Australia;9. Earth Dynamics Research Group, TIGeR (The Institute of Geoscience Research), Department of Applied Geology, Curtin University, Perth, Australia;10. Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, USA;11. Department of Computer Science, University of Idaho, Moscow, ID, 83843, USA;1. Departamento de Geología Regional, Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México, DF, Mexico;2. National Taiwan Normal University, Department of Earth Sciences, 88 Tingzhou Road Section 4, Taipei 11677, Taiwan;3. Department of Geology, St. Mary''s University, Halifax, Nova Scotia, Canada B3H 3C3;4. Department of Energy, Halifax, Nova Scotia B3J 3J9, Canada;1. Wuhan Center of Geological Survey, China Geological Survey, Wuhan 430205, China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Department of Earth and Environmental Sciences, University of Windsor, Ontario, Canada;4. State Key Lab of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;5. Key Laboratory of Marine Hydrocarbon Resources Environmental Geology, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;6. Key Laboratory of Depositional Mineralization & Sedimentary Minerals, Shandong University of Science and Technology, Qingdao 266590, China;7. School of Earth Sciences, China University of Geosciences Wuhan, Wuhan 430074, China;1. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China;2. Guangdong Provincal Key Lab of Geodynamics and Geohazards, Sun Yat-sen University, Guangzhou 510275, China;3. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;4. Bureau of Xinjiang Geology and Mineral Resources Development, Urumqi 830000, China |
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| Abstract: | Global-scale cycling of silicon through the biosphere, atmosphere, and hydrosphere has received much attention although, silicon cycling in the Earth’s lithosphere remains poorly understood. As the products of internal heat and material exchange, igneous rocks preserve significant information of silicon migration through the lithosphere. Here we report silicon isotopic compositions of nine peraluminous granites from the Chinese Altai, which forms part of the Central Asian Orogenic Belt. These rocks are characterized by the heaviest δ30Si values (?0.13 ± 0.03‰ to +0.78 ± 0.05‰) compared to global granites, with a linear variation in the silicon isotopic values against silica content, with high silica-rich granites displaying more depleted isotopic compositions. In conjunction with the whole rock weakly negative ?Nd(t) and uniform δ26Mg values, as well as high δ18O values, we suggest that the δ30Si values of these granites were mainly inherited from the magma source, rather than produced by magmatic fractionation. In addition, the wide range of initial 87Sr/86Sr ratios and high Ba content of the samples suggest the role of aqueous fluids. The Chinese Altai is considered to have formed through accretion of volcanic arcs associated with subduction of the Paleo-Asian oceanic lithosphere. The magma derived through partial melting of metasomatic mantle scavenges the heavy 30Si isotopes derived through fluids released from oceanic sediments and transfers to the upper crust where partial melting of crustal sedimentary rocks occur. Mixing of these two melts generated the peraluminous granites. Our study offers a novel insight into a potentially important mechanism of silicon cycling in the lithosphere. |
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