近日，英国圣安德鲁斯大学Joshua M. Garber团队研究了Samail蛇绿岩下快速俯冲起始时的剪切加热。这一研究成果于2025年6月2日发表在《自然—地球科学》上。
蛇绿岩下的变质底被认为记录了俯冲的开始。然而，俯冲起始期间的构造和热机制尚不明确，部分原因是单一变质作用持续时间的不确定性。研究组使用化学绘图和来自萨马尔蛇绿岩（阿曼和阿拉伯联合酋长国）变质底面的石榴石晶体的扩散速度测定法表明，在峰值温度条件下，高温（≥750°C）变质作用迅速，持续时间≤1 Myr（潜在值≤100 kyr）。
锆石U-Pb年龄和来自同一岩石的新石榴石-全岩-锆石Lu-Hf数据支持了较短的持续时间，与之前对≥8 Myr变质持续时间的推断形成了对比 。这些观测结果名义上与致密下板块的自发下沉一致。然而，快速变质时间尺度不能仅通过与并置的海洋地幔的传导热平衡来解释。一种可能的解释是，新生板块界面上的相对运动驱动了耗散加热。这种解释解释了时间尺度、变质作用的空间模式以及独立于其他地球动力学变量的单一压力-温度条件的全球相似性。
附：英文原文
Title: Shear heating during rapid subduction initiation beneath the Samail Ophiolite
Author: Garber, Joshua M., Rioux, Matthew, Smye, Andrew J., Cruz-Uribe, Alicia M., Baker, Peter L., Vervoort, Jeffrey D., Searle, Michael P., Feineman, Maureen D.
Issue&Volume: 2025-06-02
Abstract: Metamorphic soles beneath ophiolites are thought to record subduction initiation. However, there is ambiguity about the tectonic and thermal mechanisms operative during subduction initiation, arising partly from uncertainty in the duration of sole metamorphism. Here we use chemical mapping and diffusion speedometry of garnet crystals from the metamorphic sole of the Samail Ophiolite (Oman and United Arab Emirates) to show that high-temperature (≥750°C) metamorphism was rapid, lasting ≤1Myr (potentially ≤100kyr) at peak temperature conditions. The short durations are supported by zircon U–Pb ages and new garnet–whole-rock–zircon Lu–Hf data from the same rocks, contrasting with previous inferences for ≥8Myr metamorphic durations. These observations are nominally consistent with the spontaneous sinking of a dense lower plate. However, the rapid metamorphic timescales cannot be accounted for solely by conductive thermal equilibration with juxtaposed oceanic mantle. One potential explanation is dissipative heating driven by relative motion across the nascent plate interface. This interpretation accounts for the timescales, the spatial pattern of metamorphism and the global similarities in sole pressure–temperature conditions independent of other geodynamic variables.
DOI: 10.1038/s41561-025-01711-6
Source: https://www.nature.com/articles/s41561-025-01711-6