This work deals with the preliminary relationship between strain path and strain partitioning pattern in a sinistral transpressional zone, Lancangjiang shear zone, located to the southeast of Tibet. Various ductile rocks provide an opportunity to investig
Structural analyses show that the Ailaoshan-Red River shear zone （ASRRSZ） in Ailao Mountain is composed of three different deformational domains. These domains may represent three episodes of left-lateral slip experienced by the ASRRSZ. The first episode of such deformation occurred throughout the eastern high-grade belt of the ASRRSZ under a transtensional regime and produced L- type tectonites of amphibolite grade. The second episode of left-lateral slip formed high strain zones overprinting the high-grade belt. Its deformational mechanism is similar to simple shear and the deformed rocks are L-S mylonites of greenschist grade. The third episode of left-lateral slip took place chiefly in a western low-grade belt of the ASRRSZ. This deformation occurred in a transpressional regime, formed an overall structure pattern of a sinistral thrust system and produced phyllonites of low-greenschist grade. Geochronological data indicated that the three episodes of left-lateral slip happened before ～58-56 Ma, at least from ～27 Ma to 22 Ma and at ～13-12 Ma respectively. The first episode of slip in the ASRRSZ appeared to correspond to the initial collision of India and Asia at ～60 Ma. The second episode took place almost at the same time as the most intensive compression and uplift in Tibet. The latest event might represent a further eastward material flow in Tibet after ～16-13 Ma. Thus, the ASRRSZ of southeastern Asia probably experienced three main episodes of Tertiary left- lateral slip in the course of intracontinental convergence since the India-Asia collision.
The Xainza-Dinggye Normal Fault System (XDNFS) is a large-scale nearly-north-south trending exten-sional structure across central and southern Tibet. Its middle segment developed in Tethys Himalaya with features of earlier magmatic core complex and later normal faults dipping moderately to northwest-west. The magmatic core complex is made up by mylonitic leucogrante with a low-angle detachment fault on the top of it and overlain by lower-grade meta-sedimentary rocks. The structural pattern of the southern segment of XDNFS take the shape of a detachment fault dipping to southeast-east with the High-Himalayan rock series as the lower plate. The Southern Tibetan Detachment System (STDS) is expressed as a ductile shear zone composed of mylonitic leucogranite in the studied area of this note. STDS was cut by the later XDNFS, which presents that nearly-east-west striking STDS is not the controlling or adjusting structure of the nearly-north-south trending ex-tensional structures. The origin of
