近日，中国科学院地质与地球物理研究所Enbo Fan及其团队成员，在研究缅甸大陆俯冲带的地幔流动和橄榄石组构转换中取得一项新成果。相关论文于2024年1月11日发表在《地质学》杂志上。

研究对最近部署在缅甸中部46个台站记录的剪切波的分裂进行分析，以揭示介于80和100公里板块轮廓之间，夹在从地幔楔尖到弧后的平行海沟快速取向之间，垂直于沟槽的快速取向。快速取向的剧烈变化表明，地幔楔体中橄榄石组构类型的转变与角流相结合。冷大陆俯冲作用和以部分熔融为主导的剪应力降低分别有利于B型和C或E型橄榄石组构的形成。

据悉，矿物物理学和地震学的主要进展之一是，认识到不同的橄榄石组构类型受海洋俯冲系统中不同的温度、剪切应力和含水量的作用。各学者对俯冲大陆板块上方的地幔楔中，不同橄榄石组构类型的分布和地球动力学过程仍知之甚少。

附：英文原文

Title: Mantle flow and olivine fabric transition in the Myanmar continental subduction zone

Author: Enbo Fan, Yinshuang Ai, Stephen S. Gao, Yumei He, Kelly H. Liu, Mingming Jiang, Guangbing Hou, Shun Yang, Chit Thet Mon, Myo Thant, Kyaing Sein

Issue&Volume: 2024-01-11

Abstract: One of the major advances in mineral physics and seismology is the realization that different olivine fabric types are functions of temperature, shear stress, and water content in oceanic subducting systems. The distribution of different olivine fabric types and geodynamic processes in the mantle wedge above a subducting continental slab remain poorly understood. Here, based on splitting analysis of shear waves recorded by 46 stations recently deployed in central Myanmar, we reveal trench-perpendicular fast orientations between the 80 and 100 km slab contours sandwiched between trench-parallel fast orientations from the mantle wedge tip to the backarc. The dramatic change in fast orientations indicates the transition of olivine fabric types in the mantle wedge combined with corner flow. Cold continental subduction and shear stress reduction caused by partial melting favor B-type and C- or E-type olivine fabrics, respectively.

DOI: 10.1130/G51698.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51698.1/632700/Mantle-flow-and-olivine-fabric-transition-in-the