Anatomy of the Zhangshudun ophiolitic melange in the northeastern Jiangxi and its enlightenment to the evolution of Neoproterozoic South China Ocean basin

The northeastern Jiangxi ophiolitic melange is one of the most typical geological entities in Jiangnan orogenic belt.Through the anatomy of outcrop of Zhangshudun ophiolite melange with large-scale lithologic mapping plus structural analysis, it was confirmed that the blocks includes 0.9~1 Ga ophiolite of oceanic crust fragment and 0.8~1 Ga island arc volcanic-sediments.The matrix includes about 1 Ga ophiolite component, 0.9~1 Ga ocean basin sediments and 830~1000 Ma clastic flysch matrix.The melange generally presents a network structure trending northeast.The structural deformation was characterized by ductile-plastic thrust-shear deformation from northwest to southeast in the emplacement period, and was superimposed by late thrust-sliding nappe and strike-slipping structures.Based on the understanding of anatomical mapping and regional data, the Zhangshudun ophiolitic melange is considered to be the product of ocean-continent conversion processes from the closure of the back arc ocean basin to the arc-continent collision, and the final closure time of the South China Ocean basin was 780 Ma.These achievements enrich the thematic mapping method of ophiolitic melange, and are of great significance for understanding the evolution of ocean basin and orogenic process.