关键词: 印度-欧亚大陆碰撞, 青藏高原, 始新世, 侵入岩, 地球化学, 地壳加厚, 远程岩浆响应

Abstract: The India-Eurasia collision is one of the most significant Cenozoic geological events on Earth. However, the understanding of the collisional process and its remote magmatic response remains highly controversial. This study presents zircon U-Pb geochronology, whole-rock geochemistry, and Sr-Nd isotopic data for Eocene intrusive rocks from the Yaduo and Yawa areas in the Central-Southern Qinghai-Xizang Plateau, and discusses their petrogenesis. We integrate these data with a regional comparison of contemporaneous Eocene magmatic rocks, to constrain the India-Eurasia collision process and its remote response from a magmatic perspective. The diorite porphyry from the Yaduo area of the Southern Qiangtang terrane was formed at ~37 Ma and exhibit adakitic characteristics, interpreted as derived from fractional crystallization of lithospheric mantle-derived basaltic melts. The granitoidsfrom the Yawa area in the Lhasa terrane were formed at 55-54 Ma, and belonging to weakly peraluminous I-type granites, originating from partial melting of crustal materials. Based on these data, integrated with a comprehensive comparison of Eocene intermediate-felsic magmatic rocks in the southern Qinghai-Xizang Plateau, we propose that the initial India-Eurasia collision occurred at ~58 Ma; At ~52 Ma, crustal thickening resulting from the collision reached its peak, followed by slab breakoff, which triggered extensive magmatism; After ~45 Ma, the continued northward subduction of the Indian continental lithosphere drove intracontinental subduction of the lithosphere of the Lhasa terrane beneath the South Qiangtang terrane.

Key words: the India-Eurasia collision, Qinghai-Xizang Plateau, Eocene, intrusive rocks, geochemistry, crustal thickening, remote magmatic response