Zircon U-Pb age and Hf-O isotope insights into genesis of Permian Tarim felsic rocks,NW China: Implications for crustal melting in response to a mantle plume |
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| Institution: | 1. Key Laboratory of Marine Sedimentology and Environmental Geology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China;2. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China;3. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;1. Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, NSW 2522, Australia;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. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China;2. Xi’an Centre of Geological Survey, China Geological Survey, Xi’an 710054, China;3. Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Mineral, Shandong University of Science and Technology, China;4. Department of Geological Sciences, 355 Williamson Hall, University of Florida, Gainesville, FL 32611, USA;5. Shaanxi Nuclear Industry Geology Surveying Institute, Xi’an 710100, China;6. Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049, China;1. Chengdu University of Technology, Chengdu 610059, China;2. Chengdu Center, China Geological Survey, Chengdu 610081, China;3. Land and Resources Department of Tibet Province, Lasa, Tibet 850000, China;4. Geological Team 5 of the Tibet Bureau of Geology and Mineral Exploration and Development, Golmud, Qinghai 816000, China;1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. University of Chinese Academy of Sciences, Beijing 10049, China;3. Guangzhou Marine Geological Survey, Guangzhou 510760, China;4. Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964, USA;5. Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences), Ministry of Education, Wuhan 430074, China;6. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 10037, China |
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| Abstract: | Deciphering the contribution of crustal materials to A-type granites is critical to understanding their petrogenesis. Abundant alkaline syenitic and granitic intrusions distributed in Tarim Large Igneous Province, NW China, offer a good opportunity to address relevant issues. This paper presents new zircon Hf-O isotopic data and U-Pb dates on these intrusions, together with whole-rock geochemical compositions, to constrain crustal melting processes associated with a mantle plume. The ～280 Ma Xiaohaizi quartz syenite porphyry and syenite exhibit identical zircon δ18O values of 4.40 ± 0.34‰ (2σ) and 4.48 ± 0.28‰ (2σ), respectively, corresponding to whole-rock δ18O values of 5.6‰ and 6.0‰, respectively. These values are similar to mantle value and suggest an origin of closed-system fractional crystallization from Tarim plume-derived melts. In contrast, the ～275 Ma Halajun A-type granites have higher δ18O values (8.82–9.26‰) than the mantle. Together with their whole-rock εNd(t) (?2.0–+0.6) and zircon εHf(t) (?0.6–+1.5) values, they were derived from mixing between crust- and mantle-derived melts. These felsic rocks thus record crustal melting above the Tarim mantle plume. At ～280–275 Ma, melts derived from decompression melting of Tarim mantle plume were emplaced into the crust, where fractional crystallization of a common parental magma generated mafic-ultramafic complex, syenite, and quartz syenite porphyry as exemplified in the Xiaohaizi region. Meanwhile, partial melting of upper crustal materials would occur in response to basaltic magma underplating. The resultant partial melts mixed with Tarim plume-derived basaltic magmas coupled with fractional crystallization led to formation of the Halajun A-type granites. |
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