近日，英国南安普顿大学Catherine A. Rychert团队研究了古代构造对小安的列斯玄武岩板块的地震成像。该项研究成果发表在2025年4月9日出版的《自然》杂志上。

在俯冲带，岩石圈物质通过上地幔下降到地幔过渡带（MTZ），在那里它可能会继续沉入下地幔或停滞。影响这种流动的几个因素可能很重要，包括化学不均匀性。然而，事实证明，对这些地幔流动的严格限制以及影响它们的确切因素具有挑战性。

研究组使用P-to-S接收器函数对小安的列斯俯冲带下方的俯冲板块和MTZ进行成像。他们在板块内200公里宽的区域上描绘了一个单一的超深（>700公里）660公里的不连续性，伴随着附近的双660不连续相（正常和超深）。

结合地球动力学和波形建模表明，这一观测结果不能用典型地幔成分中的温度效应来解释，而是需要一个富含玄武岩的大型化学异常，在单一的660深部位置最强。推测的玄武岩特征位于俯冲灭绝扩张脊的拟议位置附近，玄武岩可能以更大的比例存在。该发现表明，过去的构造事件给板块带来了化学异质性，而这种异质性反过来可能会影响板块下沉的内在趋势。

附：英文原文

Title: Seismic imaging of a basaltic Lesser Antilles slab from ancient tectonics

Author: Yang, Xusong, Xie, Yujiang, Rychert, Catherine A., Harmon, Nicholas, Goes, Saskia, Rietbrock, Andreas, Lynch, Lloyd

Issue&Volume: 2025-04-09

Abstract: At subduction zones, lithospheric material descends through the upper mantle to the mantle transition zone (MTZ), where it may continue to sink into the lower mantle or stagnate1,2. Several factors may be important in influencing this flow, including chemical heterogeneity3,4,5. However, tight constraints on these mantle flows and the exact factors that affect them have proved challenging. We use P-to-S receiver functions to image the subducting slab and the MTZ beneath the Lesser Antilles subduction zone. We image a singular, superdeep (>700km) 660-km discontinuity over a 200-km-wide zone within the slab, accompanied by nearby double 660 discontinuity phases (normal and superdeep). Combined geodynamic and waveform modelling shows that this observation cannot be explained by temperature effects in typical mantle compositions but requires a large basalt-rich chemical anomaly, strongest in the location of the singular, deep 660. The inferred basalt signature is near the proposed location of a subducted extinct spreading ridge6,7, where basalt is probably present in greater proportions. Our finding suggests that past tectonic events impart chemical heterogeneity into slabs, and the heterogeneities, in turn, may affect the inherent tendency of the slab to sink.

DOI: 10.1038/s41586-025-08754-0

Source: https://www.nature.com/articles/s41586-025-08754-0