GEOCHEMISTRY CONSTRAIN ON TECTONIC EVOLUTION OF PALEO-TETHYS IN SE YUNNAN,CHINA

There has been a long\|term debate about the Paleo\|Tethyan Ocean in South China continent. Based on the geological and geochemical studies, it is suggested that there exist two tectonic belts in SE Yunnan, SW China called Ailao Shan zone and Shizong—Mile zone, which separate Yangtze Block, Cathysian Block and Indo\|China Block from each other. The evolutionary history and its geodynamics of these suture zones are correlated with the Paleo\|Tethyan Ocean. Both of the zones are keys to understanding whether the Paleo\|Tethyan Ocean extended from Western Yunnan area to east of the South China continent. The Ailao Shan belt consists of Red River fault, Ailao Shan fault, Shuanggou fault and Huashan—Yayi fault, which are the boundaries of the Ailao Shan basement metamorphic belt, ophiolitic melange belt and Island\|arc volcanic\|sediments belt, respectively.The ophiolitic melange belt is characterized by the existence of the ophiolite in Shuanggou area, which represents the relicts of the oceanic crust of the Ailao Shan Ocean. In addition, there exist volcanic rocks in west of the ophiolitic melange belt in Jingdong area. The geochemical characteristics of basalts in Jingdong are similar to that of the E\|MORB. Synthesized studies on geochemistry and tectonics suggest that the basalts in Jingdong area were formed in an extensional rift setting in Devonian.