CHARACTERISTICS OF IMPORTANT FAULTS AND DIVISION OF TECTONIC UNITS IN THE WEST OF SANJIANG OROGENIC BELTS, YUNNAN PROVINCE

Through data collection and field investigation, some new knowledge is gained on the location, characteristics and north-south connection of important faults in the west of Sanjiang orogenic belts, Yunnan Province, as described below. 1) Nujiang fault is a third-order tectonic unit boundary fault between Gaoligong Mountain metamorphic basement complex and Bingzhongluo block in northwestern Yunnan, as well as between Luxi fault block and Baoshan block in southwestern Yunnan. 2) As Bangongcuo-Dongqiao fault extends to Yunnan, the north and middle sections are connected with the east-inclined thrust nappe fault located on the main peak of Gaoligong Mountains, and the southern section is known as Longling-Ruili fault. 3) Gaoligongshan fault and Longling-Ruili fault are the boundary structures of first-order tectonic unit between Tengchong orogenic belt and Sanjiang orogenic belt. 4) The Shuangjiang-Zhutang fault and Cangyuan fault on the east and west sides of Changning-Menglian junction zone extend northward to northwestern Yunnan and are connected with Fugong fault and Bangdang fault respectively on the west slope of Biluo Snow Mountain. 5) The Dimaluo-Changning-Menglian junction zone is a second-order tectonic unit, bordered by the second-order tectonic units of Chongshan-Lincang block on the east and Bingzhongluo-Baoshan block on the west respectively. The western Sanjiang orogenic belts are divided into 2 second-order and 7 third-order tectonic units.