南京大学王小林团队在研究双俯冲作用对长期大陆构造和次大陆地幔温度的控制中取得新进展。相关论文于2024年8月19日发表在《地质学》杂志上。

研究人员建立了二维数值模型，通过系统地测试大陆上部板块下方的单一和向内倾斜的双俯冲，以及大陆碰撞对这些系统的影响，来探讨复杂俯冲系统的演化。与单一俯冲模式相比，向内倾斜的双俯冲模式表现为海沟迁移受阻，过量下沉的板块增强了上升流地幔的体积。与单次俯冲的边缘盆地相比，双重俯冲在更广阔的区域内将更大更热的地幔拉到大陆之下，使得次大陆升温约200°C。

当碰撞堵塞双俯冲系统的一个边缘时，另一个边缘则遵循迁移的单俯冲带的演化，尽管其特征是继承了双俯冲阶段的持续较高的地幔温度和强烈的上升流，以及大规模的上部板块伸展。研究人员将模拟结果与比例参数进行比较，以验证该机制在新生代南海和新元古代扬子地块(中国东南部)构造中的可行性。研究结果强调，在这些构造中，向内倾斜的双重俯冲为长期的大规模大陆扩张、较高的次大陆升温，和不容易与单一俯冲带动力学相协调的通道地幔流提供了背景。

据研究人员介绍，汇聚边缘的复杂性通常包括俯冲带的相互作用，有许多“双重”俯冲的地质记录。

附：英文原文

Title: Double subduction controls on long-lived continental tectonics and subcontinental mantle temperatures

Author: Lin-Sen Li, Fabio A. Capitanio, Peter A. Cawood, Ben-Jun Wu, Ming-Guo Zhai, Xiao-Lei Wang

Issue&Volume: 2024-08-19

Abstract: The complexities of convergent margins commonly include the interactions of subduction zones, with many geological records of “double” subduction. Here, we build two-dimensional numerical models to explore the evolution of complex subduction systems by systematically testing single and inward-dipping double subduction beneath a continental upper plate and the impact of continental collision on these systems. When compared to single subduction models, the inward-dipping double subduction shows hindered trench migrations and larger volumes of upwelling mantle enhanced by excess sinking slab mass. Double subduction draws larger volumes of hotter mantle beneath the continent in an area much broader than the marginal basins of single subductions, contributing to subcontinental heating by ～200 °C. As collision jams one margin of a double subduction system, the other margin follows the evolution of migrating single subduction zones, although characterized by persisting higher mantle temperatures and strong upwellings, inherited from the double subduction stage, and large-scale upper plate extension. The modeling outcomes are compared to scaling arguments to test the viability of the mechanism proposed for tectonics of the Cenozoic South China Sea and Neoproterozoic Yangtze Block (southeastern China), where the inward-dipping double subduction provides a context for protracted large-scale continental extension, hotter subcontinental temperatures, and channeled mantle flow not easily reconciled with the dynamics of single subduction zones.

DOI: 10.1130/G52232.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G52232.1/646730/Double-subduction-controls-on-long-lived