近日，德国基尔大学Kaj Hoernle团队研究了西阿留申群岛的硫化物承载板坯熔化：板坯衍生熔体中嗜铜质元素丰度的影响和大陆地壳的起源。相关论文于2025年11月4日发表在《地质学》杂志上。

部分熔体俯冲洋嵴（板熔体）被认为在成矿过程和大陆嵴的形成中起重要作用，但由于缺乏喷发的板熔体，阻碍了对其作用的直接评价。来自西阿留申群岛的原始镁流纹岩的摩尔浓度为Mg/Mg+Fe^T >0.60，代表了俯冲太平洋板块中洋中脊玄武岩（MORB）的未变质熔体。

研究组发现硬石膏斑晶和角闪石成分的存在表明结晶的高度氧化条件（ΔNNO≥+1）。尽管这些条件和矿物组合中没有硫化物，岩石仍表现出强烈的亲铜元素分选比（Ag/Cu ~10 × MORB和Bi/Cu ~100 × MORB），表明它们的地球化学特征是由板熔融过程中单硫化物固溶体（MSS）相的存在所施加的。

镁质流纹英安岩中的亲铜元素丰度可以通过在2 GPa和900°C条件下、伴随MSS存在的MORB榴辉岩部分熔融过程进行定量解释。除Ag和Bi外，板状熔体中Cu、Se、Pt和Au等强亲铜元素含量较低，因此在上地幔条件下输送这些元素的能力有限。镁流纹岩中显著的Ag/Cu和Bi/Cu比值进一步表明，在整个地球历史中，板块岩浆可能是大陆砾石中亲铜元素特征的重要贡献者。

附：英文原文

Title: Melting of sulfide-bearing slab beneath the Western Aleutian Arc: Implications for chalcophile element abundances in slab-derived melts and the origin of continental crust

Author: Maxim Portnyagin, Roman Botcharnikov, Gene Yogodzinski, Dieter Garbe-Schnberg, Kaj Hoernle

Issue&Volume: 2025-11-04

Abstract: Partial melts subducting oceanic crust (slab melts) have been proposed to play an important role in ore-forming processes and in the generation of continental crust, but the scarcity of erupted slab melts hampers direct evaluation of their role. Primitive Mg-rhyodacites with molar Mg/Mg+FeT >0.60 from the Western Aleutians represent nearly unmodified melts from eclogitized mid-ocean-ridge basalt (MORB) of the subducting Pacific plate. Here, we show that the presence of anhydrite phenocrysts and hornblende compositions indicate highly oxidizing conditions (ΔNNO ≥+1) of crystallization. Despite these conditions and the absence of sulfides in the mineral assemblage, the rocks exhibit strongly fractionated chalcophile element ratios (Ag/Cu ～10 × MORB and Bi/Cu ～100 × MORB), suggesting their geochemical signatures were imposed by the presence of monosulfide solid solution (MSS) phase during slab melting. The chalcophile element abundances in the Mg-rhyodacites can be quantitatively explained by partial melting of MORB eclogite at 2 GPa and 900°C in the presence of MSS. With the exception of Ag and Bi, slab melts have low contents of strongly chalcophile elements, such as Cu, Se, Pt, and Au, and therefore a limited capacity to transport these elements under upper mantle conditions. The distinctively high Ag/Cu and Bi/Cu ratios in the Mg-rhyodacites further suggest that slab-derived magmas may have been significant contributors to the chalcophile element signatures of the continental crust throughout Earth’s history.

DOI: 10.1130/G53585.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53585.1/666400/Melting-of-sulfide-bearing-slab-beneath-the