Late Neoarchean geodynamic evolution: Evidence from the metavolcanic rocks of the Western Shandong Terrane, North China Craton

摘要

Late Neoarchean metavolcanic rocks are widely distributed in the Western Shandong Terrane (WST). They are classified as similar to 2590-2580 Ma tholeiites (Group MB-1), similar to 2550-2530 Ma tholeiites (Group MB-2), calc-alkaline basalts (Group MB-3), high-Si adakites (Group MAD) and similar to 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 depletedmantle (GroupMB-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 similar to 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 similar to 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 similar to 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. (c) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.