TECTONIC CONSTRAINTS FROM CHINESE CRATONIC BLOCKS FOR THE RECONSTRUCTION OF RODINIA
Li Jianghai (Department of Geology, Peking University, Beijing 100871) Mu Jian (Exploration Department, China National Petroleum Cooperation,Beijing 100724)
The argument on tectonic position of Chinese cratonic blocks(CCBs) in reconstruction of Rodinia is due to inadequent tectonic constratints and correlation of CCBs with other cratonic blocks of the world. Tectonic analysis of CCBs on available data indicates that there are several Grenville age orogenic belts in China.\;North Qinling orogenic belt(NQOB) along southern margin of North China Craton(NCC),mainly consists of back arc basin assemblages, island arc complex, and Mesoproterozoic ophiolite relics (1.0Ga). To its southern side NQOB is reworked and truncated by South Qinling Dabie Phanerozoic orogenic belt. Its tectonic history could be summarized as rifting of southern margin of NCC(1.85Ga-1.40Ga), followed by active continental marginal collision between NCC and an island arc(1.0Ga). It is an accretionary orogen along southern margin of NCC, rather than multiphase collisional orogen between yangzte craton(YC) and NCC. Along the northern margin of NCC are also identified the Mesoproterozoic orogenic records(1.0-1.4Ga). The Mesoproterozoic marginal orogenies exert a strong influence on North China cratonic basin, leading to the occurrence of a major unconformity (1.00Ga) separting from underlying Mesoproterozoic and overlying Neoproterozoic cratonic cover sequences, asssociated with widespread marine regression and tectonic difference of NCC from west to east(～ 1.0Ga). \;Jiangnan orogenic belt located in southeast margin of YC could be subdivided into ophiolite(1.00 Ga), back arc turbidite(1.10-0.90Ga), island arc volcanics granites (0.96-0.93Ga) and S type granites (0.90-0.96Ga). Its tectonic evolution could be interpreted as subduction along SE margin of YC(1.30-1.20Ga) followed by collision of YC Jiangnan island arcs Cathaysia. Cathaysia records at least three major Precambrian tectono thermal events (1.0Ga, 1.8-1.9Ga, 2.4-2.7Ga),among which 1.0Ga event is clearly associated with collision of YC with Cathaysia. Moreover, Mesoproterozoic orogenic records(1.0-1.2Ga) and ophiolite(1.0Ga) have been also recognized along western margin of YC, resulted tectonism along the active continental margin.\;The delineation of Mesoproterozoic tectonic unites and relevant episodes suggest that CCBs should be ancient fragmented cartonic blocks, rather than isolated continental nuclei's. The tectonic correlation of CCBs with other cratons of the world on Mesoproterozoic tectonics will provide important constraints for reconstruction of Rodinia.