Late Paleozoic-Mesozoic subduction and accretion of the Paleo-Pacific Plate:Insights from ophiolitic rocks in the Wandashan accretionary complex,NE China |
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| Authors: | Yong Liang Han Zheng Huan Li Thomas J.Algeo Xiao-Meng Sun |
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| Affiliation: | 1. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;2. State Key Laboratory of Biogeology and Environment Geology, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;3. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;4. Department of Geology, University of Cincinnati, Cincinnati, OH 42221-0013, USA;5. College of Earth Sciences, Jilin University, Changchun 130061, China |
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| Abstract: | The Wandashan accretionary complex(AC),consisting of the Raohe and Yuejinshan complexes,is located on the continental margin of Northeast Asia and represents an excellent source of information about Paleo-Pacific subduction and accretion.However,the protolith nature and tectonic evolution of the Wandashan AC are under debate.This contribution reports new geochronological,geochemical,and Sr-Nd-Pb-Hf isotopic data for ophiolitic rocks from the Wandashan AC.The 169-166 Ma plagioclasites and homogeneous gabbros from the Raohe complex are OIBs while 228-214 Ma homogeneous gabbros are continental VABs.Cumulate gabbros from the Yuejinshan complex formed at 280-278 Ma and～220 Ma and have similar characteristics with E-MORB and N-MORB,respectively.They are BABBs and their primary magma was derived from a source region between EMI and EMII that was affected by con-tinental crustal contamination as well as subduction-zone metasomatism.Combined with previous stud-ies,we suggest that the onset of subduction of the Paleo-Pacific Plate was in the Early Permian.Subsequently,a back-arc basin,whose present suture is on the eastern margin of the Jiamusi Massif,formed and widened during 280-232 Ma,after which the basin closed and BABBs were emplaced to form the Yuejinshan complex during 210-180 Ma.The formation of VABs of the Raohe complex is coincident with the closure of the back-arc basin,and together with the 169-166 Ma OIBs,they constitute a major part of the Raohe complex.The accretionary process was completed during 133-131 Ma.Taken together,the ophiolitic rocks indicating multistage magmatism in the Paleo-Wandashan region recorded the formation-closure process of back-arc basin and the accretionary process of the Wandashan AC,during the westward subduction of the Paleo-Pacific plate.The back-arc basin identified in our study sheds new lights on geodynamic evolution model of subduction and accretion of the Paleo-Pacific Plate on the continental margin of NE Asia. |
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| Keywords: | Ophiolite Magma chemistry Tectonic evolution Back-arc basin Raohe complex Yuejinshan complex |
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