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

MA Xuxuan ¹Joseph G.MEERT ²CAO Wenrong ³TIAN Zuolin ⁴LIU Dongliang ¹XIONG Fahui ⁴LI Haibing¹

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作者信息

1. 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,China
2. Department of Geological Sciences,Neil Opdyke Paleomagnetic Laboratory,University of Florida,241 Williamson Hall,Gainesville,FL 32611,USA
3. Department of Geological Sciences and Engineering,University of Nevada,Reno,MS-172,1664 N.Virginia St.,Reno,NV 89557,USA
4. Key Laboratory of Continental Tectonics and Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China
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Abstract

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.

Key words

mantle/magmatic flare-up/subduction-collision transition/Nymo intrusive complex/Gangdese/Tibet

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基金项目

National Natural Science Foundation of China(42272267)

Research Grants of Chinese Academy of Geological Sciences(JKYQN202309)

National Key Research and Development Project"Key scientific issues of transformative technology"(2019YFA0708604)

second Tibetan Plateau Scientific Expedition and Research Program(STEP)Grant(2019QZKK0802)

second Tibetan Plateau Scientific Expedition and Research Program(STEP)Grant(2019QZKK0901)

Scientific Investigation on Basic Resources of Ministry of Science and Technology(2021FY100101)

Geological Survey of China(DD20221630)

Geological Survey of China(DD20242126)

出版年

2024

地质学报(英文版)

中国地质学会

地质学报(英文版)

CSTPCD

影响因子：1.414

ISSN：1000-9515

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