Oxidized Late Mesozoic subcontinental lithospheric mantle beneath the eastern North China Craton: A clue to understanding cratonic destruction |
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| Institution: | 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 100049, China;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;1. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;2. Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia;3. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China;1. School of Earth Sciences, Lanzhou University, Lanzhou 730000, China;2. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;3. Department of Earth Sciences, Durham University, Durham DH1 3LE, UK;4. School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China;5. Radiogenic Isotope Facility, School of Earth Sciences, The University of Queensland, Brisbane QLD 4072, Australia |
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| Abstract: | Despite the critical influence of oxidation state on the geochemical and geodynamic evolution of Earth, its impact on the longevity of cratons is poorly understood. To address this issue, we investigated the redox state of the Late Mesozoic subcontinental lithospheric mantle (SCLM) beneath the eastern North China Craton (NCC), which was destroyed during the Phanerozoic. We report the occurrence of high-Fo olivine (Fo > 87, where Fo = atomic Mg/(Mg + Fe2+)) within Early Cretaceous basalts; these olivines show extremely low Ti (<60 ppm) contents, high δ18O (5.8‰–7.2‰) values, and relatively cool crystallization temperatures (1125 to 1218 °C). These features support derivation of the lavas from highly refractory and cold SCLM. The relatively low partition coefficients of vanadium between olivine and whole rocks (0.019–0.025) indicate a high fO2 for the Early Cretaceous basalts and their mantle sources (ΔQFM = +1.0 and ΔQFM = +1.5, respectively), and, consequently, an oxidized Late Mesozoic SCLM beneath the eastern NCC. The high degree of oxidation of the mantle was caused by the ingress of hydrous melts and/or fluids released from a subducting slab during the Phanerozoic. We propose that oxidization of the SCLM softened the mantle, which triggered the removal of the cratonic root beneath the eastern NCC. The results highlight the crucial role of oxidation state in craton stability. |
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