Late Neoarchean geodynamic evolution: Evidence from the metavolcanic rocks of the Western Shandong Terrane,North China Craton |
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Institution: | 1. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;2. Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences, Bejing 100037, China;3. Faculty of Geosciences and Engineering, Xi''an Shiyou University, Xi''an 710065, China;4. Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China |
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Abstract: | Late Neoarchean metavolcanic rocks are widely distributed in the Western Shandong Terrane (WST). They are classified as ~2590–2580 Ma tholeiites (Group MB-1), ~2550–2530 Ma tholeiites (Group MB-2), calc-alkaline basalts (Group MB-3), high-Si adakites (Group MAD) and ~2520–2500 Ma tholeiites (Group MB-4) based on zircon U-Pb chronological and geochemical data. Their parental magmas have complex origins and were derived from a depleted mantle wedge enriched by slab-derived melts or fluids (Group MB-1); an unaltered depleted mantle (Group MB-2); the delaminated lower crustal materials (Group MAD); a strongly melt- and fluid-metasomatized depleted mantle (Group MB-3); and a fluid- and sediment-metasomatized asthenospheric mantle (Group MB-4). The late Neoarchean geodynamic evolution of the WST revealed by these multi-genetic volcanic rocks can be summarized as follows: (1) an ~2.62–2.53 Ga eastward subduction operated along the ancient continental margin, followed by delamination of unstable continental lithosphere in the back-arc region during ~2.60–2.53 Ga; and (2) delamination-derived mantle magmas ascended and caused the regional extension, further inducing the asthenosphere to passively rise and the back-arc basin to open during ~2.52–2.50 Ga. The above intense mantle magmatism and crust-mantle interactions have consumed abundant mantle energy and facilitated the continental stratification and final cratonization of the WST. |
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