Geochemistry of middle-late Mesozoic mafic intrusions in the eastern North China Craton: New insights on lithospheric thinning and decratonization |
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| Institution: | 1. School of Earth Science, China University of Geoscience, Wuhan 430074, China;2. Huazhong Tectonomechanical Research Center, Wuhan 430074, China;3. Institute of Geology and Mechanics, Chinese Academy of Sciences, Beijing 100081, China;4. School of Earth and Space Sciences, Peking University, Beijing 100871, China;5. College of Earth Sciences, Jilin University, Jianshe Street 2199, Changchun 13006, Jilin, China;6. Center for Global Tectonics, School of Earth Sciences, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;7. Three Gorges Research Center for Geohazards, Ministry of Education, China University of Geosciences, Wuhan 430074, China;8. California Institute of Technology Division of Geological & Planetary Sciences, Pasadena, CA, United States of America;9. Department of Earth Sciences, Nanjing University, Nanjing 210093, China;10. Middle East Technical University, Department of Geological Engineering, 06800 Ankara, Turkey;1. Key Lab of Submarine Geosciences and Prospecting Techniques, MOE, Institute for Advanced Ocean Study, College of Marine Geosciences, Ocean University of China, Qingdao 266100, China;2. Laboratory for Marine Geology and Environment, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;3. State Key Laboratory of Continental Dynamics, Northwest University, Xi''an 710069, China;4. Tianjin North China Geological Exploration Bureau, Tianjin 300170, China;5. UCD School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland;1. School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, China;2. Department of Earth Sciences, School of Physical Sciences, The University of Adelaide, SA 5005, Australia;3. Geological Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Republic of Korea;1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;2. CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;3. College of Oceanography, Hohai University, Nanjing 210098, China |
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| Abstract: | We present detailed geochronological, geochemical and Sr-Nd-Pb isotopic data for late Mesozoic mafic intrusions in the Taili region (western Liaodong Province) of the eastern North China Craton (NCC). We obtained laser-ablation inductively-coupled plasma mass spectrometry U-Pb zircon ages from lamprophyres with ages ranging from 139 to 162 Ma and diorites with clusters of ages at 226 ± 11 Ma, 165 ± 5.8 Ma and 140 ± 4.8 Ma. We interpret the Triassic zircons in diorites to be inherited from the Paleo-Asian Ocean slab. Both the lamprophyres and diorites contain abundant inherited grains (2644–2456 Ma) that were likely derived from the ancient NCC basement, reflecting a contribution from old lower crustal material. Like contemporaneous late Mesozoic mafic rocks in the Jiaodong and Liaodong Peninsula areas of the NCC, the Taili lamprophyres reveal a strong subduction signature in their normalized trace element patterns, including depletion of high field strength elements and enrichment of large ion lithophile elements. The rare-earth element patterns of the Taili intermediate-mafic intrusions are best explained if they were principally derived from partial melting of amphibole-bearing lherzolite in the spinel-garnet transition zone. Slab-derived melts likely contributed to the formation of late Mesozoic mafic rocks along three margins of the craton: due to accretion of the Yangtze Block along the southern margin of the craton, subduction of the Paleo-Asian Ocean along the northern margin, and subduction of the Paleo-Pacific oceanic plate along the eastern margin of NCC. We present a synthesis of the geochemical, spatial, and temporal patterns of magmatic rocks and periods of deformation that contributed to decratonization of the NCC in response to the Mesozoic tectonic evolution of adjacent plates along its northern, southern, and eastern margins. |
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