Recognition of two-phases of deformation in the Gyirong-Sa' gya zone, southern Xizang during the Jurassic and its geological implications

The Jurassic Lure and Weimei Formations in the Gyirong-Sa' gya zone, southern Xizang went through twophases of deformation during the Jurassic, including the intermediate to deep bedding shearing and homoclinal folding in the early phase and intermediate depth folding and thrusting in the late phase. The two-phases of deformation have mirrored the subduction of the Tethyan Ocean from south to north and India-Eurasian plate collision and mountain building, respectively. The deformational styles and package patterns have recorded the history and processes of plate subduction, collision and mountain building. The early deformation resulted in the stratigraphic repetition. This is why the Jurassic strata are so tremendous in thickness that they can hardly correlate with those in the Gyangze and Yamzho Yumco areas in Xizang.