Mantle Driven Early Eocene Magmatic Flare-up of the Gangdese Arc,Tibet:A Case Study on the Nymo Intrusive ComplexOACSTPCD
Mantle Driven Early Eocene Magmatic Flare-up of the Gangdese Arc,Tibet:A Case Study on the Nymo Intrusive Complex
Magmatic periodicity is recognized in continental arcs worldwide,but the mechanism responsible for punctuated arc magmatism is controversial.Continental arcs in the Trans-Himalayan orogenic system display episodic magmatism and the most voluminous flare-up in this system was in early Eocene during the transition from subduction to collision.The close association of the flare-up with collision is intriguing.Our study employs zircon Lu-Hf and bulk rock Sr-Nd isotopes,along with mineral geochemistry,to track the melt sources of the Nymo intrusive complex and the role of mantle magma during the early Eocene flare-up of the Gangdese arc,Tibet.The Nymo intrusive complex is composed of gabbronorite,diorite,quartz diorite,and granodiorite which define an arc-related calc-alkaline suite.Zircon U-Pb ages reveal that the complex was emplaced between～50-47 Ma.Zircon Hf isotopes yield εHf(t)values of 8.2-13.1,while whole-rock Sr and Nd isotopes yield εNd(t)values of 2.7-6.5 indicative of magmatism dominated by melting of a juvenile mantle source with only minor crustal assimilation(～15％-25％)as indicated by assimilation and fractional crystallization modeling.Together with published data,the early Eocene magmatic flare-up was likely triggered by slab breakoff of subducted oceanic lithosphere at depths shallower than the overriding plate.The early Eocene magmatic flare-up may have contributed to crustal thickening of the Gangdese arc.This study provides important insights into the magmatic flare-up and its significant role in the generation of large batholiths during the transition from subduction to collision.
MA Xuxuan;Joseph G.MEERT;CAO Wenrong;TIAN Zuolin;LIU Dongliang;XIONG Fahui;LI Haibing
Key Laboratory of Continental Tectonics and Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China||Jiangsu Donghai Continental Deep Borehole Crustal Activity National Observation and Research Station,Donghai,Jiangsu 222300,ChinaDepartment of Geological Sciences,Neil Opdyke Paleomagnetic Laboratory,University of Florida,241 Williamson Hall,Gainesville,FL 32611,USADepartment of Geological Sciences and Engineering,University of Nevada,Reno,MS-172,1664 N.Virginia St.,Reno,NV 89557,USAKey Laboratory of Continental Tectonics and Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China
mantlemagmatic flare-upsubduction-collision transitionNymo intrusive complexGangdeseTibet
《地质学报（英文版）》 2024 (004)
878-903 / 26
Profound discussion and perceptive comments of Roberto Weinberg on the first draft are greatly appreciated.We benefited from the discussion with Zhu Zhiyong and She Yuwei.Mao Xiaohong,Xu Xiangzhen,and Shi Bin are thanked for their help in the EMPA and image scanning analysis.Xiang Hua helped us to model the factional crystallization and partial melting processes using the GeoPS v3.3 version.We are indebted to two anonymous reviewers for their constructive comments and editors for their efficient handling on our manuscript.This study was co-supported by the National Natural Science Foundation of China(Grant No.42272267),the Research Grants of Chinese Academy of Geological Sciences(Grant No.JKYQN202309),the National Key Research and Development Project"Key scientific issues of transformative technology"(Grant No.2019YFA0708604),the second Tibetan Plateau Scientific Expedition and Research Program(STEP)Grant(Grant Nos.2019QZKK0802,2019QZKK0901),the Scientific Investigation on Basic Resources of Ministry of Science and Technology(Grant No.2021FY100101),and the Geological Survey of China(Grant Nos.DD20221630,DD20242126).
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