Proterozoic tectonics of eastern South China and their Paleo-location reconstruction
The Meso-and Neo-proterozoic geological records in eastern South China are the key carri-ers for understanding the Columbia and Rodinia supercontinent cycles and the geodynamic evolution of East Asia,which are yet uncertain so far.This paper presents an overview of key geological observa-tions for the southwest Hainan,eastern Yangtze,and Cathaysia with respect to Proterozoic tectonics.Our data show that the SW Hainan in the Mesoproterozoic(～1.45 Ga)developed in a non-orogenic rift setting in the Columbia interior which was undergone by the～1.05 Ga high-grade metamorphism.SW Hainan might be a part of the Mesoproterozoic Albany-Fraser Orogen at～1.30-1.05 Ga,and,subse-quently moved to the margin of Rodinia.Cathaysia and eastern Yangtze display distinct geological signatures in the early Neoproterozoic and Cathaysia remained separated from Yangtze until at least～1.0 Ga,even～0.83 Ga.The～1.0-0.9 Ga felsic igneous rocks in Cathaysia are dominated by negative εHf(t)values,and distinct from those in the coeval Shuangxiwu arc with positive εHf(t)values.Such signatures might be the response to the subduction of the Proto-Ghats Ocean,herein named the Early Neoproterozoic Proto-Cathaysia Orogen.The～870-830 Ma(mainly 850-830 Ma)igneous rocks are extensive in the Huaiyu and Jiangnan Orogen but poor in Cathaysia.The Cathaysia Neoproterozoic sedimentary rocks are signed by～980 Ma detrital grains but dominated by～860-830 Ma detrital zircons for the Jiangnan and Huaiyu sedimentary rocks.Banxi,Likou and Mamianshan groups and their equivalents are extensively developed in Cathaysia and Huaiyu,and the Jiangnan Orogen,respectively,and are characterized by the rift-related sedimentary rocks and bi-model igneous rocks with the formation ages of～810-750 Ma.They are separated from the Cangshuipu and Luojiamen conglomerates across an angular unconformity or unconformably underlain by the Lengjiaxi and Xikou groups.In combination with the available data,it is proposed for a long-lived Neoproterozoic(～0.97-0.83 Ga)and westward-subducted Proto-Huanan arc-trench system signed by～0.98-0.88 Ga Shuangxiwu intra-oceanic arc,0.87-0.83 Ga Huaiyu continental arc and 0.87-0.83 Ga Jiangnan intra-continental back-arc basin,which switched from an intra-oceanic to a continental Andean margin setting at～0.87 Ga.Such a system lay along strike from the synchronous Eastern Ghats and South Delhi orogen at the periphery of Rodinia.Our data revealed the united proto-South China being created by the～830-810 Ma Jiangnan orogenesis in response to the assemblage of the Yangtze with Cathaysia,which was followed by the post-orogenic rifting due to the breakup of Rodinia.
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