Nd isotopic constraints on crustal formation in the North China Craton |
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| Institution: | 1. Department of Geology, Jilin University, 79 Jianshejie, 130061 Changchun, China;2. Department of Earth Sciences, University of Hong Kong, Pokfulam Road, Hong Kong, China;3. Department of Applied Geology, Curtin University of Technology, P.O. Box U1987, Perth, Western Australia 6845, Australia;1. División de Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), Camino a la Presa San José 2055, San Luis Potosí, Mexico;2. Department of Geology and Natural Resources, Institute of Geosciences, PO Box 6152, University of Campinas – UNICAMP, 13083-970 Campinas, SP, Brazil;3. Department of Geology (Center of Advanced Study), Institute of Sciences, Banaras Hindu University (BHU), Varanasi 221005, India;4. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences (IGG-CAS), 19 Beitucheng West Road, Chaoyang, Beijing – 100029, China;5. Department of Geology, Institute of Earth Sciences, Bundelkhand University, Jhansi, India;6. CICTERRA-CONICET-UNC, Av. Vélez Sarsfield 1611, Pab. Geol., X5016CGA-Córdoba, Argentina;7. 24E Mayur Residency Ext, Indra Nagar, Lucknow 226015, India;1. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA;2. School of the Environment, Washington State University, Pullman, WA, USA;1. The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China;2. Shenyang Institute of Geology and Mineral Resource, Shenyang 110034, China;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;3. Department of Earth Sciences, Carleton University, Ottawa, ON K1S 5B6, Canada;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China;2. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada;3. Shaanxi Earthquake Agency, Xi''an 710068, China;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China;2. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | Recent tectonic analysis suggests that the North China Craton consists of two Archean continental blocks, called the Eastern and Western Blocks, separated by the Paleoproterozoic Trans-North China Orogen. Although the published geochronological data are not sufficient to constrain the detailed tectonothermal evolution of the craton, the available Nd isotopic data show some important differences in Nd model ages between the tectonic units. The Eastern Block shows two main Nd model age peaks, one between 3.6 and 3.2 Ga and the other between 3.0 and 2.6 Ga. Limited Nd isotopic data from the Western Block show a large range of model ages between 3.2 and 2.4 Ga. These differences are consistent with the recently-proposed model.The Nd isotopic data from mantle-derived mafic rocks indicate that the mantle beneath the North China Craton was depleted in the Archean, consistent with major crustal growth during this period. In the Paleoproterozoic, however, the mantle-derived mafic rocks show negative εNd(t) values, implying crustal contamination. This may have resulted from subduction and collision between the Eastern and Western Block, implying that the mechanisms of crustal formation and evolution may have been different between the Archean and Paleoproterozoic.The North China Craton was re-activated by addition of mantle-derived magma into the lower crust in the late Mesozoic, resulting in rejuvenation of the lower crust. This indicates that underplating is also an important mechanism for continental addition, although in this case it may not equate to crustal growth, since it was preceded by removal of lithospheric mantle and possible some lower crust. |
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