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Title:: Neoproterozoic Post-collision Magmatism in South Qilian Orogen, China: Evidenced by Geochronology and Geochemistry

Author(s):: MA Jian-jun; WANG Heng; HE Chuan; WANG Lu; WANG Qin-yan; CHEN Neng-song; 1. School of Earth Sciences, China University of Geosciences, Wuhan 430074, Hubei, China;2. School of Earth Sciences, Zhejiang University, Hangzhou 310027, Zhejiang, China

Keywords:: granite; zircon U-Pb age; post-collisional magmatism; Rodinia supercontinent; North Wulan terrane; South Qilian Orogen

Abstract:: The protracted post-collisional magmatism in response to assembly of the global Rodinia supercontinent in Northwest China is recorded by the magmatism of Kekesha granite pluton in North Wulan terrane of South Qilian Orogen, China. LA-ICP-MS zircon U-Pb dating yields crystallization ages of (861±9)-(863±4)Ma and (827±6)-(830±8)Ma for Kekesha granodiorites and monzogranites, respectively, with a metamorphic age of (463±3)Ma. Combined with the previous ages, Kekesha granite pluton may be produced by two stages of magmatism around 860 Ma and 810-830 Ma. The granodiorites and monzogranites are characterized respectively by weakly peraluminous and weakly-strongly peraluminous but totally high potassium calc-alkaline S-type granites, and the precursor magma is formed in the extensional tectonic environment of the post-collision stage, and the source rocks are dominantly metagraywackes with magmatic partial melting temperature of 800 ℃ and pressures of 0.9-1.4 GPa. In conclusion, the main collision phase of North Wulan terrane ends before 860 Ma.