Mantle Driven Early Eocene Magmatic Flare-up of the Gangdese Arc, Tibet: A Case Study on the Nymo Intrusive Complex

作     者：MA Xuxuan Joseph GMEERT CAO Wenrong TIAN Zuolin LIU Dongliang XIONG Fahui LI Haibing MA Xuxuan;Joseph G.MEERT;CAO Wenrong;TIAN Zuolin;LIU Dongliang;XIONG Fahui;LI Haibing

作者机构：Key Laboratory of Continental Tectonics and Dynamics of Ministry of Natural ResourcesInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China Jiangsu Donghai Continental Deep Borehole Crustal Activity National Observation and Research StationDonghaiJiangsu 222300China Department of Geological SciencesNeil Opdyke Paleomagnetic LaboratoryUniversity of Florida241 Williamson HallGainesvilleFL 32611USA Department of Geological Sciences and EngineeringUniversity of NevadaRenoMS-1721664 N.Virginia St.RenoNV 89557USA 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2024年第98卷第4期

页      面：878-903页

核心收录：

学科分类：070904[理学-构造地质学] 070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 

基　　金：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) the Geological Survey of China (Grant Nos. DD20221630, DD20242126) 

主　　题：mantle magmatic flare-up subduction–collision transition Nymo intrusive complex Gangdese Tibet 

摘      要：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.