澳大利亚地球科学局Noreen J. Evans研究组在最新研究中，报道了低δ18o弧岩浆的板块成因。该研究于2025年1月16日发表于国际一流学术期刊《地质学》杂志上。

据悉，板块构造是地幔、地幔和地表储层之间物质循环的主要方法。锆石中的氧同位素（18O/16O, δ18O）主要通过探测同位素重质壳上物质的存在，通过俯冲作用来跟踪岩石成分。同位素光特征相对较少，表明高温热液强度的再循环可以忽略不计。

研究团队报告了511澳大利亚维多利亚州西部马斯塔夫利带。这些岩石表现出两个阶段的混合历史：(1)恒定、高放射性成因的εHf随δ18O的减小而减小，表明亚地幔δ18O初始组成，被解释为亚弧地幔被低δ18O的板块熔体和/或流体污染；(2) εHf随δ18O的增大而减小，表明受乡村岩石浊积岩污染。

这些新数据表明，高温热液可以通过俯冲带循环，并改变弧下地幔的组成。研究组展示了板块撕裂是如何驱动这一过程的，它与德拉美洲造山带构造的联系，以及对环超大陆边缘的影响。

附：英文原文

Title: A slab origin for low-δ18O arc magmas

Author: David R. Mole, Christopher J. Lewis, Simon Bodorkos, James L. Crowley, Anthony Schofield, Stacey O. Curtis, Noreen J. Evans

Issue&Volume: 2025-01-16

Abstract: Plate tectonics is the primary method for cycling of material between the mantle, crust, and surface reservoirs of our planet. Oxygen isotopes (18O/16O, δ18O) in zircon have been shown to track source components through subduction, primarily by detecting the presence of isotopically heavy supracrustal material. Isotopically light signatures are relatively rare, suggesting recycling of high-temperature hydrothermal sources is negligible. Here, we report light δ18O data from magmatic-arc rocks of the 511500 Ma Stavely Belt in western Victoria, Australia. These rocks demonstrate a two-stage mixing history: (1) constant, highly radiogenic εHf with decreasing δ18O, indicating sub-mantle δ18O initial compositions, interpreted to represent a sub-arc mantle contaminated with low-δ18O slab melts and/or fluids; and (2) decreasing εHf with increasing δ18O, implying crustal contamination with country-rock turbidites. These new data suggest that high-temperature hydrothermal sources can be recycled through subduction zones and alter the composition of the sub-arc mantle. We demonstrate how slab tearing could have driven this process, its connection to the architecture of the Delamerian Orogen, and implications for circum-supercontinent margins.

DOI: 10.1130/G52782.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G52782.1/651412/A-slab-origin-for-low-18O-arc-magmas