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 

机构地区：[1]Key Laboratory of Continental Tectonics and Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [2]Jiangsu Donghai Continental Deep Borehole Crustal Activity National Observation and Research Station,Donghai,Jiangsu 222300,China [3]Department of Geological Sciences,Neil Opdyke Paleomagnetic Laboratory,University of Florida,241 Williamson Hall,Gainesville,FL 32611,USA [4]Department of Geological Sciences and Engineering,University of Nevada,Reno,MS-172,1664 N.Virginia St.,Reno,NV 89557,USA

出　　处：《Acta Geologica Sinica(English Edition)》2024年第4期878-903,共26页地质学报（英文版）

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)。

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.

关 键 词：MANTLE magmatic flare-up subduction–collision transition Nymo intrusive complex GANGDESE TIBET 

分 类 号：P542.5[天文地球—构造地质学] P534.613[天文地球—地质学]