The Mesozoic Closure of the Paleo-Tethys Ocean: Constraints from Zircon U–Pb Ages, Hf and Nd Isotopes of The Granitic Plutons in the Hoh-Xil-Songpan-Ganzi

Abstract

Dong, J.-H.; Zou, H.; Liu, H.; Li, Y., and Jiang, X.-W., 2019. The Mesozoic closure of the Paleo-Tethys Ocean: Constraints from zircon u–pb ages, hf and Nd isotopes of the granitic plutons in the Hoh-Xil-Songpan-Ganzi. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 101–106. Coconut Creek (Florida), ISSN 0749-0208.The Hoh-Xil-Songpan-Ganzi (HXSG) complex is a large triangular fold located in the eastern part of the Tibet Plateau, which recorded of the Closure of Paleo-Tethys Ocean and recorded the tectonic activities of convergence between the three blocks of the Yangtze, North China and Qiangtang during early Mesozoic. This contribution combines geological and Hf-Nd isotopic data for igneous rocks from the HXSG complex, together with the salient features to gain insights into the crustal architecture and tectonic evolution. Two period tectonic-magmatism activities of sys-collision magmatism (ca. 243-227 Ma) and post-collision magmatism (ca. 219-185 Ma) have been recognized in the HXSG complex during Early Mesozoic. The large-scale intermediate-felsic magmatism include high Ba-Sr granite, adakite granitoids, I-type and A-type granitoids, strong aluminous leucogranites. The depth of the source region is different from the mantle, the crust and mantle transition zone, the lower crust and the upper middle crust. As for the closure of the Paleo-Tethys Ocean, the subduction of the Paleo-Tethys oceanic lithosphere leads to the convergence of the North China Block, the Yangtze Block and the Qiangtang Block, the HXSG complex shortened and thickened, the thickened lithosphere was delaminated, then the asthenosphere further upwelled to melting the thicken lower crust, the HXSG complex entered the intraplate extensional tectonic setting, the magmatism involved the partial melting of the lithospheric mantle and even the asthenosphere mantle.