Distribution and Evolution of OPS from Proterozoic to Early Paleozoic in the Cathaysian Orogen
The theory and method of Ocean Plate Stratigraphy(abbreviated as OPS)is used for the recon-struction of the Cathaysia Orogen evolution during the Proterozoic to the Early Paleozoic in this study.This paper systematically collects 96 records of oceanic crust renmant or OPS(including igneous rock series of ocean ridge,ocean island and intra-oceanic arc,and depositional sequences of seamount,pelagic setting and trench).The records were dated and studied in geochemistry.Thirteen of the 96 records are investigated in our field work and sampled.This study also collects 85 non-OPS records on the setting of ocean convergence including continental marginal arc and volcanic arc superimposed on the rifted block.Fifty nine of the 85 re-cords were dated and studied in geochemistry.Other 26 of them were not dated,but is described and sampled in our fieldwork.Based on the systematic collection of dating and geochemistry study,this paper mainly re-veals the distribution of OPS and tectonic evolution of the Cathaysia Orogen in the Proterozoic to the Early Paleozoic.The Cathaysian Orogen spatially could be divided into the Jiangshao-Chenzhou-Qinfang major su-ture zone,Wuyi-Ganzhou multi-island arc-basin system and the Southeast Coast multi-island arc-basin sys-tem.The Jiangshao-Chenzhou-Qinfang major suture zone mainly involved to the Chencai-Longyou,Shen-zhengqiao-Shenshan,Yingyangguan and Nuodong accreiontary wedges with ophiolite renmants,as well as the Shaoxing-Lanxi accretionary arc and Qinfang residual ocean basin.The Wuyi-Ganzhou multi-island arc-basin system mainly went through the Luoxiao arc,Ganzhou interarc basin,North Wuyi arc,South Wuyi arc,and the Nanping-Ninghua tectonic melange belt.The Southeast Coast multi-island arc-basin system in-volved to the Longquan-Zhenghe-Dapu and Guizi-Shiwo accretionary wedges with ophiolite renmant,as well as the Yunkai arc,southern Guangdong arc-back basin and southeast coastal massifs.According to the spatial and temporary distributions of OPS and volcanic arcs,the evolution of the Cathaysian Orogen could be divided into seven stages:(1)1800-1200 Ma,extension and formation of ocean basin;(2)1200-820 Ma,convergence of ocean basin;(3)820-635 Ma,subduction of ocean basin and accretion of arcs;(4)635-541 Ma,a transitional stage from convergence to expansion of ocean basin;(5)541-458 Ma,expansion of ocean basin;(6)458-443 Ma,ocean subduction and accretion of arcs with continents;(7)443-420 Ma,residual stage of ocean basin.
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