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,Xizang.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 yieldεHf(t)values of 8.2–13.1,while whole-rock Sr and Nd isotopes yieldεNd(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.
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)。
作者简介
first author\corresponding author:MA Xuxuan,male,born in 1986 in Linquan,Anhui Province,Ph.D.,graduated from Nanjing University,associate researcher of the Institute of Geology,Chinese Academy of Geological Sciences.He is now interested in the study on magmatic structures,and dynamics of magma chamber-mush.E-mail:xuxuan.ma@hotmail.com.
