The South China block-Indochina collision: Where, when, and how?

摘要: This study uses new field observations and existing studies to shed light on the origin significance of two NW-SE striking orogens in NW NE Vietnam. We conclude that architecture each belt is a stack NE-directed nappes formed either under deep ductile synmetamorphic conditions, or shallow depth SW parts, respectively. The Song Ma zone Chay ophiolitic melange represent sutures. However, Late Permian Da Babu mafic rocks are not ophiolites but intraplate basalts related Emeishan plume. A Triassic unconformity, 225-205 postorogenic plutonism, 250-230 syntectonic metamorphism support an Early Middle age for these tectonic events. Both belts due SW-directed subduction with arc magmatism, ocean closure, continental collision. Though contemporary S-dipping zones might explain structural evolution belts, single convergent system, offset by Tertiary Red River fault, preferred as this S-directed better accounts magmatism. scenario discussed general geodynamic framework SE Asia.