中国科学院地质与地球物理研究所Xu Mengyu团队，报道了中国东北增生复合体中下弧地壳岩石折返揭示的俯冲侵蚀。这一研究成果于2024年2月28日发表在国际顶尖学术期刊《地质学》上。

团队人员对来自该增生杂岩中的角闪岩，其原岩(基于全岩微量元素和Sr-Nd-Hf同位素)为基性大陆弧岩浆岩(255-249Ma；锆石核U-Pb年龄)。受矿物地球化学约束的相平衡模拟表明，角闪岩及其围岩首先在251-244Ma(锆石边缘U-Pb年龄 )被加热到低麻粒岩相(750-800°C，约 7kbar)，随后在213-187Ma(钛铁矿和磷灰石U-Pb年龄)之前随着压力的增加(8-9kbar)冷却到约700°C。

为了解释增生杂岩中下弧地壳岩性的出现及其变质史，团队研究人员提出俯冲板块强烈侵蚀了弧前地壳，使板块界面向陆推进，并刮擦了旧弧下形成的角闪岩和围岩，最终沿俯冲通道被挖出，成为增生杂岩的组成部分。该案例研究举例说明了发生在古造山带中的强烈俯冲侵蚀的直接岩石学证据，这意味着整个弧前地壳的消耗可能只发生在50m.y.内。

据了解，汇聚边缘的俯冲侵蚀是大陆地壳破坏(再循环和改造)的主要机制。但由于缺乏直接证据，要确定化石俯冲带的侵蚀事件及其强度并不容易。中国东北的黑龙江增生杂岩形成于早中生代古太平洋俯冲期间。

附：英文原文

Title: Subduction erosion revealed by exhumed lower arc crustal rocks in an accretionary complex, northeastern China

Author: Mengyu Xu, Wenjiao Xiao, Kai Liu, Bo Wan, Ross N. Mitchell, Gideon Rosenbaum, Hao Wang

Issue&Volume: 2024-02-28

Abstract: Subduction erosion at convergent margins is a leading mechanism for the destruction (recycling and reworking) of continental crust. But because of the lack of direct evidence, it is not straightforward to identify erosive events and their intensities in fossil subduction zones. The Heilongjiang accretionary complex in northeastern China was formed during the early Mesozoic subduction of the Paleo-Pacific Ocean. We investigated amphibolites from this accretionary complex, whose protoliths (based on whole-rock trace elements and Sr-Nd-Hf isotopes) were mafic continental arc magmatic rocks (255-249 Ma; zircon core U-Pb ages) from the upper plate. Phase equilibria modeling constrained by mineral geochemistry indicates that the amphibolites and their wall rocks were first heated to low granulite facies (750-800 °C, ～7 kbar) at 251-244 Ma (zircon rim U-Pb ages) and then cooled to ～700 °C with increasing pressure (8-9 kbar) before 213-187 Ma (titanite and apatite U-Pb ages). To explain the occurrence of the lower arc crustal lithologies in the accretionary complex and their metamorphic history, we propose that the subducting plate strongly eroded the forearc crust, allowing the plate interface to advance landward and scrape the amphibolites and wall rocks formed under the old arc, which finally were exhumed along the subduction channel and became components of the complex. The case study exemplifies direct petrological evidence of strong subduction erosion occurring in an ancient orogen, thus implying that consumption of the entire forearc crust could occur within only ～50 m.y.

DOI: 10.1130/G51803.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G51803.1/635695/Subduction-erosion-revealed-by-exhumed-lower-arc