近日，吉林大学杨德彬等人，报道了亚洲东北部渐新世俯冲混杂岩的熔融作用及其地幔动力学。该项研究成果发表在2024年4月12日出版的《地质学》上。

据悉，俯冲混杂岩的熔融可能会将物质从板块-地幔界面输送到俯冲带的地幔楔。混合底辟模型是根据室内实验和热力学模拟的结果建立的。然而，人们对俯冲带中混杂底辟的熔融机制仍不清楚。

该团队成员为了进一步限制混杂底辟的地幔动态，对亚洲东北部大陆边缘渐新世碱性中性岩进行了详细研究。全岩地球化学和Sr-Nd-Pb-Mg-Zn同位素数据显示，这些岩石是由混杂岩部分熔融形成的。研究人员认为底辟是渐新世混杂岩熔融的机制。研究还在东北亚东部发现了由混杂岩熔融形成的较年轻的岩石，这意味着自渐新世以来的这种岩浆活动向东移动。

研究结果和构造环境显示，混杂底辟的熔融优先发生在构造转换期间，例如由垂直于海沟的地幔流引发的弧后盆地的形成。具有不可压缩应力场的低黏度地幔引发了混杂底辟的熔融。由于混杂底辟和碳化橄榄岩之间的相互作用，使得混杂岩-地幔相互作用的深度被限制在软流圈内，比以往研究推断的深度要深。

附：英文原文

Title: Oligocene melting of subducted mélange and its mantle dynamics in northeast Asia

Author: Ke-Chun Hong, Feng Wang, Si-Wen Zhang, Wen-Liang Xu, Yi-Ni Wang, De-Bin Yang

Issue&Volume: 2024-04-12

Abstract: Melting of subducted mélange can potentially transport mass from the slab-mantle interface to the mantle wedge in subduction zones. The mélange diapir model was primarily proposed from the results of laboratory experiments and thermodynamic modeling. However, the melting mechanisms of mélange diapirs in subduction zones remain unclear. To further constrain the mantle dynamics of a mélange diapir, we studied Oligocene alkaline intermediate rocks on the northeast Asian continental margin. We report whole-rock geochemical and Sr-Nd-Pb-Mg-Zn isotope data and show that these rocks formed by partial melting of mélange. We conclude that a diapir was the mechanism for Oligocene melting of the mélange. We also identified younger rocks formed by melting of mélange in the eastern part of northeast Asia, implying an eastward shift in such magmatism since the Oligocene. Our results and the tectonic setting indicate that melting of mélange diapirs occurred preferentially during tectonic transitions, such as the formation of a back-arc basin triggered by trench-perpendicular mantle flow. The low-viscosity mantle with an incompressible stress field triggered melting of the mélange diapirs. Interactions occurred between the mélange diapirs and carbonated peridotites, constraining the depth of mélange-mantle interactions to the asthenosphere, which is deeper than the depth inferred in previous studies.

DOI: 10.1130/G52115.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52115.1/638086/Oligocene-melting-of-subducted-melange-and-itsredirectedFrom=fulltext