铜（Cu）同位素研究对于理解高温地质过程中硫化物与硅酸盐间Cu的分配具有重要意义。目前，高温地质过程的Cu同位素研究仍很薄弱，对于以下两个重要科学问题仍无定论：（1）地幔部分熔融过程中是否会发生Cu同位素分馏；（2）洋脊之下的软流圈地幔中Cu同位素是否均一。本项目提出可检验假说“地幔低程度部分熔融形成的熔体富集重Cu同位素”，这种富集熔体的地幔交代作用是造成上地幔Cu同位素不均一性的可能原因之一。本项目拟以东太平洋洋隆（5º-15º N）两侧海山玄武岩为例，检验该假说。这些海山玄武岩在主量元素、微量元素、Sr-Nd-Pb-Hf同位素和Fe同位素组成上都存在极大变化，地幔源区组分极不均一。研究表明富集组分形成于地幔低程度部分熔融产生的熔体的地幔交代作用。因此，这些海山玄武岩是检验上述假说、探究Cu同位素地幔不均一性的理想样品。本研究是对非传统稳定同位素理论、地幔不均一性认识的重要补充和发展。

The isotope systematics of Copper (Cu) are significant in studying the Cu partitioning between silicates and sulfides during high-temperature geological processes. At present, studies in the high-temperature Cu isotope systematics are limited and are still in the process of data accumulation. It is still controversial on questions of 1) whether Cu isotopes would fractionate during mantle melting, and 2) whether the asthenospheric mantle beneath the ocean ridges has heterogeneous Cu isotope composition. This proposal develops a testable hypothesis that “melts produced by low-degree mantle melting should have heavy Cu isotope compositions”, and metasomatism of such low-degree melts may be one of the mechanisms that cause the Cu isotope heterogeneity in the upper mantle. This proposal plans to test the above hypothesis by using the near-EPR (5º-15º N) seamounts as a case study. This sample suit has been well studied with great variations in major and trace elements, Sr-Nd-Pb-Hf radiogenic isotopes and stable Fe isotopes, which shows a compositionally heterogeneous mantle source. The enriched mantle component was explained to originate from the metasomatism of melts produced by low-degree mantle melting. Therefore, these seamount samples have the best chance to test the above hypothesis and explore the potential Cu isotope heterogeneity in the asthenospheric mantle beneath oceanic ridges. This study has great potentials of enriching and developing the theories of the nontraditional stable isotopes and mantle heterogeneity.