New constraints on the structure, thermochronology, and timing of the Ailao Shan-Red River shear zone, SE Asia

New structural, petrographic, and Ar-40/Ar-39 data constrain the kinematics of the ASRR (Ailao Shan-Red River shear zone). In the XueLong Shan (XLS), geochronological data reveal Triassic, Early Tertiary, and Oligo-Miocene th ermal events. The latter event (33-26Ma) corresponds to cooling during left -lateral shear. In the FanSiPan (FSP) range, thrusting of the SaPa nappe, l inked to left-lateral deformation, and cooling of the FSP granite occurred at approximate to 35Ma. Rapid cooling resumed at 25-29Ma as a result of upl ift within the transtensive ASRR. In the DayNuiConVoi (DNCV), foliation tre nds NW-SE, but is deflected near large-scale shear planes. Stretching linea tion is nearly horizontal. On steep foliations, shear criteria indicate lef t-lateral shear sense. Zones with flatter foliations show compatible shear senses. Petrographic data indicate decompression from approximate to6:5kbar during left-lateral shear (temperatures >700 degreesC). Ar-40/Ar-39 data i mply rapid cooling from above 350 degreesC to below 150 degreesC between 25 and 22Ma without diachronisin along strike. Along the whole ASRR cooling h istories show two main episodes: (1) rapid cooling from peak metamorphism d uring left-lateral shear; (2) rapid cooling from greenschist conditions dur ing right-lateral reactivation of the ASRR. In the NW part of the ASRR (XLS , Diancang Shan), we link rapid cooling 1 to local denudations in a transpr essive environment. In the SW part (Ailao Shan and DNCV), cooling 1 resulte d from regional denudation by zipper-like tectonics in a transtensive regim e. The induced cooling diachronism observed in the Ailao Shan suggests left -lateral rates of 4 to 5 cmiyr from 27Ma until approximate to 17Ma. DNCV ro cks always stayed in a transtensive regime and do not show cooling diachron ism. The similarities of deformation kinematics along the ASRR and in the S outh China Sea confirms the causal link between continental strike-slip fau lting and marginal basin opening.