瑞士洛桑大学Chloé Bouscary团队揭示了自 200 ka 以来，亚喜马拉雅山脉发生了持续变形的现象。该研究于2023年11月15日发表于国际一流学术期刊《地质学》杂志上。

研究团队使用最近建立的 10⁵ yr 时间尺度的发光热年代学技术，量化了亚喜马拉雅山脉的折返率，该技术记录了地壳最后几公里的挖掘。发光热年代学的超低闭合温度，使得研究人员能够解析 Siwalik 组(尼泊尔)岩石的热历史，这些岩石的最高埋藏温度约为 120 °C。从尼泊尔西部到不丹东部，研究团队收集了 33 个样本，其中 22 个样本在过去的 200 k.y. 内产生了约 3-11 mm /yr 的挖掘率。

研究人员假设逆冲倾角为 30°，将这些值转换为约 6-22 mm /yr 的最小累计推力滑动率。发光热年代学数据显示，亚喜马拉雅山下的褶皱冲断带，特别是喜马拉雅主前缘逆冲断层，容纳了至少 200 ka以来喜马拉雅山汇聚的 62％。数据还显示，在这一时期，Siwalik 内部的一些冲断活动，意味着造山楔的内部已经发生了变形和应变分割。

据悉，目前，喜马拉雅主前缘逆冲断层(MFT)通过亚喜马拉雅山脉的隆起和变形，容纳了约一半的印度和欧亚构造之间的汇聚，即 12-23 mm /yr。虽然现代和百万年时间尺度的变形存在较好的记录，但几乎没有定量数据可以用来限制这一关键构造单元及其内部的第四纪时间尺度的变形率。因此，填补这一知识空白，对于更好地理解人口稠密的喜马拉雅地区的构造和地震周期至关重要。

附：英文原文

Title: Sustained deformation across the Sub-Himalayas since 200 ka

Author: Chloé Bouscary, Georgina E. King, Djordje Grujic, Jérme Lavé, Rafael Almeida, Gyrgy Hetényi, Frédéric Herman

Issue&Volume: 2023-11-15

Abstract: The Himalayan Main Frontal Thrust (MFT) currently accommodates approximately half, i.e., 12-23 mm/yr, of the convergence between the Indian and Eurasian tectonic plates by uplift and deformation of the Sub-Himalayas. While deformation is well documented at modern and million-year time scales, almost no quantitative data are available that constrain Quaternary time scale deformation rates along and within this key tectonic unit. Filling this knowledge gap is crucial to better understanding tectonics and the seismic cycle in this densely populated Himalayan region. We quantify exhumation rates in the Sub-Himalayas using the recently established luminescence thermochronometry technique over time scales of 10⁵ yr, which documents exhumation over the final few kilometers of Earth’s crust. The ultra-low closure temperature of luminescence thermochronometry enables us to resolve thermal histories from the Siwalik Group (Nepal) rocks, which have experienced maximum burial temperatures of ～120 °C. An extensive set of 33 samples was collected from western Nepal to eastern Bhutan, from which 22 yield exhumation rates of ～3-11 mm/yr over the past ～200 k.y. We converted these values to minimum cumulative thrust slip rates of ～6-22 mm/yr, assuming a thrust dip angle of 30°. Our luminescence thermochronometry results show that the Sub-Himalayan fold-and-thrust belt, particularly the MFT, accommodates at least 62% of Himalayan convergence since at least 200 ka. Our data also show activity of some intra-Siwalik thrusts throughout this period, implying that internal deformation of the orogenic wedge and strain partitioning may have occurred.

DOI: 10.1130/G51656.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51656.1/629494/Sustained-deformation-across-the-Sub-HimalayasredirectedFrom=fulltext