法国比利牛斯造山带Lherz二辉橄榄岩成因：原生vs次生

地幔橄榄岩中二辉橄榄岩通常作为低程度熔融的饱和地幔组分，常被用来厘定初始地幔的地球化学成分。然而，近年来不断有研究表明这些二辉橄榄岩可能是熔/流体交代亏损地幔形成的次生产物。关于“地幔二辉橄榄岩的成因：原生vs次生”的问题不仅直接影响被广泛接受的初始地幔成分的正确性；也涉及到大规模交代事件所需的交代介质的产生、迁移和交代机制等重要科学问题。法国Pyrenees造山带地幔橄榄岩长期以来作为研究地幔成分的重要对象，其中最大的Lherz岩体还是二辉橄榄岩(lherzolite)的英文发源地。然而，近些年来，Lherz二辉橄榄岩的原生成因也开始遭受质疑。本项目拟针对Lherz二辉橄榄岩为研究对象，采用单斜辉石原位元素-Sr同位素以及不同矿物间Sr-Nd-Hf-Fe同位素相结合，深刻揭示Lherz二辉橄榄岩的成及源岩属性，为全球地幔橄榄岩的成因研究、地幔深部岩浆过程提供理论和实际指导意义。

Orogenic lherzolites are commonly used to infer the composition of the Earth’s primitive mantle). However, an increasing set of research shows that lherzolites may form by combined processes of partial melting and melt refertilization. It is critical to distinguish between primary origin by subtle partial melting of primitive mantle and secondary origin by melt refertilization of depleted mantle. Because it may cast doubt on the accuracy of previous estimation on primitive mantle if the massive lherzolites are secondary products. Meanwhile, it has important geodynamic implications on the transformation and destabilization of ancient lithospheric mantle via melt refertilization. The Lherz massif in the French Pyrenees is a type-locality of lherzolite, of which the origin has been highly debated. We plan to use clinopyroxene in-situ elemental and Sr isotopic as well as inter-mineral Sr-Nd-Hf and Fe isotopic constraints, combined with quantitative geodynamic modelling via alphaMELTS, to determine the origin of Lherz lherzolite and constrain the nature of the source. This will provide an essential guide on the study of global mantle peridotite, mantle-crustal interaction, and the transformation and destabilization of lithospheric mantle.