The Xuelongshan high strain zone: Cenozoic structural evolution and implications for fault linkages and deformation along the Ailao Shan-Red River shear zone

New structural, geometric, petrographic, and U-Pb zircon data constrain the kinematics of the Xuelongshan high strain zone, northermost parts of the Ailao Shan-Red River shear zone. In the Xuelongshan range, mylonitic foliation mainly trends NW-SE. On steep foliation and flatted foliation, mineral stretching lineation is various, from gentle to steep, and ductile shear senses indicate a left-lateral, top-to-the-northwest shear movement on the eastern limb, and a left-lateral, top-to-the-southeast shear on the western limb of the range. These dome-related ductile geometries and kinematics, namely D1 deformation, represent regional high-temperature metamorphism due to crustal thickening. The superimposed sinistral strike-slip shearing of D2 deformation occurred locally along the earlier domal fabrics. Metamorphism, migmatization, and the emplacement of leucogranitic veins associated with partial melting were syntectonic with the regional-scale upright antiform. LA-ICP-MS U-Pb dating of zircons reveals the late Permian-Triassic and Oligocene thermal events. The latter event (ca. 33-26 Ma or possibly earlier) from the leucogranitic veins corresponds to the regional metamorphism during crustal thickening along the Xuelongshan. These data indicate that the Jiali-Xuelongshan-Diancangshan-Ailao Shan high strain zones can belong to a system around the Eastern Himalayan Syntaxis (EHS), and that the Xuelongshan zone played a role in linking other segments between the Tibet to Indochina in Cenozoic.