Tracing subducted crust in the oceanic mantle with siderophile elements and transition metal stable isotopes and implications for the sources of basaltic volcanism

为了了解地壳和地幔之间的全球物质通量，需要限制俯冲洋壳的命运及其对地幔源火山作用的贡献。辉石岩被认为是源自俯冲地壳的熔体相互作用的产物，是岩石圈洋玄武岩源区的重要组成部分。为了更全面地了解熔体-岩石相互作用过程中示踪剂分布的控制过程，提出了在辉石岩层及其邻近环境中对整个岩石和单个颗粒尺度上的高亲铁元素（HSE，包括Os同位素）和过渡金属（Fe, Cu, Ni）的稳定同位素进行联合研究。来自意大利外Ligurides的辉石岩已被证明含有地壳衍生物质，非常适合这种类型的研究。高亲铁元素和稳定同位素Fe已成为研究地幔熔体与围岩相互作用的有效工具，而Ni和Cu同位素作为地幔示踪剂的发展将为研究熔体与围岩相互作用过程中硫化物元素的分布提供新的思路。

In order to understand global material fluxes between crust and mantle, the fate of subducted oceanic crust and its contribution to mantle-derived volcanism needs to be constrained. Pyroxenites have been suggested to be products of interaction of melts derived from subducted crust and to be an important component in the source region of oceanic basalts in the lithosphere. To develop a more complete understanding of the processes controlling the distribution of tracers during melt-rock interaction, a combined study of highly siderophile elements (HSE, including Os isotopes) and stable isotopes of transition metals (Fe, Cu, Ni) on both the whole rock and individual grain scale in pyroxenite layers and their immediate surroundings is proposed. Pyroxenites from the External Ligurides, Italy, which have been demonstrated to contain crust-derived material, are ideally suited for this type of study. Highly siderophile elements and stable isotopes of Fe have been developed as useful tools to study interaction of melts with surrounding wall rock in the mantle, and coupled with development of Ni and Cu isotopes as mantle tracers will provide new insights about the distribution of sulfide-hosted elements during melt-rock interaction.