南方科技大学胡佳顺课题组最新的研究成果显示，印度-欧亚大陆聚合因被动边缘沉积俯冲而加速。相关论文于2024年11月6日发表在《自然》杂志上。

鉴于地质构造历史的内在不确定性和影响板块速度的复杂相互作用，大约65个百万年前（Ma），印度和欧亚大陆之间的聚合速度迅速增加（从大约8cm yr^-1到约为18cm yr^-1的峰值速率），被解释为是一个复杂的地质事件。

研究人员采用地球化学分析和地球动力学建模的方法，利用印度北部被动边缘的沉积物俯冲来解释这种快速会聚。通过同位素和微量元素分析，研究人员发现，在65Ma左右，随着印度和欧亚大陆的聚合的加速，陆源沉积物熔体对冈底斯岩浆岩地幔源区的贡献增强。

数值实验表明，从65Ma开始，覆盖印度北部被动边缘约1000公里宽海洋盆地的，厚度超过1公里的沉积物俯冲可能刺激了辐合速率的增加，并进一步导致了显著的地壳伸展，这与经验观测结果一致。

研究表明，印度-欧亚大陆会聚的加速，标志着被动大陆边缘沉积物的到来，将印度-欧亚大陆碰撞的初始时间限制在60Ma左右。这进一步表明，俯冲速率的暂时加速，可能是大陆组合最后阶段的一个普遍特征。

附：英文原文

Title: India–Eurasia convergence speed-up by passive-margin sediment subduction

Author: Zhou, Hao, Hu, Jiashun, Dal Zilio, Luca, Tang, Ming, Li, Keqing, Hu, Xiumian

Issue&Volume: 2024-11-06

Abstract: The fast increase of convergence rate between India and Eurasia around 65 million years ago (Ma)—from approximately 8cm yr^-1 to a peak rate of approximately 18cm yr^-1—remains a complex geological event to explain, given the inherent uncertainty surrounding the tectonic history and the intricate interplay of forces influencing plate speed. Here we use a combination of geochemical analysis and geodynamic modelling to propose that this rapid convergence can be explained by sediment subduction derived from the northern Indian passive margin. Through isotope and trace element analysis, we find an enhanced contribution of terrigenous sediment melt to the mantle source of the Gangdese magmatic rocks around 65Ma, concurrent with the acceleration of India–Eurasia convergence. Numerical experiments suggest that subduction of sediments more than 1km thick covering an approximately 1,000-km-wide ocean basin abutting the northern Indian passive margin starting from 65Ma could have spurred the increased convergence rate and further led to significant crustal extension, consistent with empirical observations. Our study implies that the acceleration of India–Eurasia convergence marks the arrival of passive-margin-derived sediments, constraining the initial India–Eurasia collision to be around 60Ma. It further suggests that temporary accelerations in subduction rates might be a common feature at the final stage of continental assembly.

DOI: 10.1038/s41586-024-08069-6

Source: https://www.nature.com/articles/s41586-024-08069-6