Structure and deformation around the Gyirong basin, north Himalaya, and onset of the south Tibetan detachment system  

作　　者：YANG XiongYing ZHANG JinJiang QI GuoWei WANG DeChao GUO Lei LI PengYuan LIU Jiang 

机构地区：[1]The Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871,China

出　　处：《Science China Earth Sciences》2009年第8期1046-1058,共13页中国科学（地球科学英文版）

基　　金：Supported by National Natural Science Foundation of China (Grant Nos. 40821002, 40572115)

摘　　要：Gyirong basin and its adjacent area are located at a special position in the Himalayan orogen, where the south Tibetan detachment system (STDS) and N-S trending rift converged. The north Himalayan orogen here can be divided into five petrologic-tectonic units successively from south to north: 1) the Greater Himalayan crystalline complex (GHC); 2) the STDS shear zone; 3) the Tethyan Himalayan sedimentary sequence (THS); 4) the late Cenozoic sedimentary basins, such as Gyirong and Oma basins; and 5) the Malashan gneiss dome. Structural studies show that this area experienced four stages of deformation: 1) the earlier south-directed thrusting, preserved both in the GHC and THS; 2) top-down-to-north slip along the STDS, normal faults related to this slip formed the early controlling structures of the Cenozoic basins,and the tilted pattern of the blocks between the basins indicated a north-directed slip; 3) east-west extension, the resultant N-S trending normal fault formed the eastern boundary of the basins; and 4) late gravitational collapse. Zircon SHRIMP U-Pb dating on the syn-deformational (leuco-) granite along the STDS indicates that the major activity of the STDS occurred at ca. 26 Ma, but its onset may have begun as early as ca. 36 Ma.Gyirong basin and its adjacent area are located at a special position in the Himalayan orogen, where the south Tibetan detachment system (STDS) and N-S trending rift converged. The north Himalayan orogen here can be divided into five petrologic-tectonic units successively from south to north: 1) the Greater Himalayan crystalline complex (GHC); 2) the STDS shear zone; 3) the Tethyan Himalayan sedimentary sequence (THS); 4) the late Cenozoic sedimentary basins, such as Gyirong and Oma basins; and 5) the Malashan gneiss dome. Structural studies show that this area experienced four stages of deformation: 1) the earlier south-directed thrusting, preserved both in the GHC and THS; 2) top-down-to-north slip along the STDS, normal faults related to this slip formed the early controlling structures of the Cenozoic basins, and the tilted pattern of the blocks between the basins indicated a north-directed slip; 3) east-west extension, the resultant N-S trending normal fault formed the eastern boundary of the basins; and 4) late gravitational collapse. Zircon SHRIMP U-Pb dating on the syn-deformational (leuco-) granite along the STDS indicates that the major activity of the STDS occurred at ca. 26 Ma, but its onset may have begun as early as ca. 36 Ma.

关 键 词：south TIBETAN DETACHMENT SYSTEM (STDS) DEFORMATION stage syn-deformational granite zircon SHRIMP U-Pb dating onset age 

分 类 号：P542[天文地球—构造地质学]