Understanding Mesozoic accretion in Southeast Asia: Significance of Triassic thermotectonism (Indosinian orogeny) in Vietnam

Results from a zircon U-Pb study of the metamorphic basement of Vietnam rev eal that a large part of the continental crust was affected by a short-live d episode of ductile deformation and high-temperature metamorphism between 258 +/- 6 Ma and 243 +/- 5 Ma. Although coincident with final stages of Nor th-South China collision (Qinling orogenesis), the thermotectonism in Vietn am was caused by accretion of Sibumasu to Indochina-South China. This accre tion event (Indosinian orogeny) has regional significance because it contri buted to the final stages of North-South China collision, an aspect not exp licitly recognized in Qinling orogenic models.