研究人员对 Cu 同位素进行研究表明，俯冲带过程和地幔熔融在弧岩浆中产生有限的 Cu 同位素分馏，相反，与 Cu 含量负相关的下地壳岩石的不均一 Cu 同位素组成表明，在弧岩浆的壳内分异过程中，存在同位素轻硫化物的分离或富集。这一发现得到下地壳镁铁质堆积体的极轻 Cu 同位素组成和厚大陆弧中分异岩浆的重 Cu 同位素组成的支持。
幔源岩浆的壳内分异作用和随后富含硫化物的镁铁质堆积体的形成，优先去除了同位素轻的 Cu，留下贫 Cu 和同位素重的大陆地壳。
据介绍，与大陆地壳的组成部分—原生弧岩浆相比，大陆地壳的铜含量非常低，这种损耗与大陆地壳的形成有着内在的联系。然而，铜的去除过程仍然是个谜。
附：英文原文
Title: Copper isotope evidence for sulfide fractionation and lower crustal foundering in making continental crust
Author: Sheng-Ao Liu, Roberta L. Rudnick, Wen-Ran Liu, Fang-Zhen Teng, Tian-Hao Wu, Ze-Zhou Wang
Issue&Volume: 2023-09-06
Abstract: The continental crust is strongly depleted in copper compared with its building blocks—primary arc magmas—and this depletion is intrinsically associated with continental crust formation. However, the process by which Cu removal occurs remains enigmatic. Here we show, using Cu isotopes, that subduction-zone processes and mantle melting produce limited fractionation of Cu isotopes in arc magmas, and, instead, the heterogeneous Cu isotopic compositions of lower crustal rocks, which negatively correlate with Cu contents, suggest segregation or accumulation of isotopically light sulfides during intracrustal differentiation of arc magmas. This is supported by the extremely light Cu isotopic compositions of lower crustal mafic cumulates and heavy Cu isotopic compositions of differentiated magmas in thick continental arcs. Intracrustal differentiation of mantle-derived magmas and subsequent foundering of sulfide-rich mafic cumulates preferentially removes isotopically light Cu, leaving a Cu-depleted and isotopically heavy continental crust.
DOI: adg6995
Source: https://www.science.org/doi/full/10.1126/sciadv.adg6995