LATE PERMIAN-TRIASSIC MAGMATIC EVOLUTION IN THE JINSHAJIANG OROGENIC BELT, SW CHINA AND IMPLICATIONS FOR OROGENIC PROCESSES FOLLOWING CLOSURE OF THE PALEO-TETHYS

摘要

Growth of continental crust involves the complex interplay of subduc-tion zone magmatism, to generate the crust, followed by stabilization through crustal thickening, magmatism and ultimately isolation from the active plate margin. The Jinshajiang orogenic belt, SW China, provides an exceptional record of continental development as the result of closure of the Paleo-Tethys seaway and ensuing collision. A compilation of U-Pb age and geochemical data for the plutonic and volcanic rocks within the southern part of the Jinshajiang orogenic belt, including new high-precision ages for the Ludian granitoid bathohth of 231 to 220 Ma, enables us to explore the interaction between magmatism and orogeny in the context of the Paleo-Tethys closure and continental amalgamation. These age and geochemical constraints, in conjunction with other geologic evidence, suggest that subduction of the Paleo-Tethys ocean dominated local tectonics prior to the Triassic, creating a volcano-plutonic arc along the eastern margin of the Qamdo-Simao terrane.