Fe和Mg作为两种常量元素，其同位素的地球化学示踪意义受到日益广泛的关注。已有研究表明基性岩浆演化过程会导致Fe同位素发生显著分馏，而Mg同位素分馏微弱。但是，部分矿物Fe、Mg同位素数据的缺乏使得基性岩矿物间Fe、Mg同位素分馏研究十分薄弱，特别是硅酸盐矿物与磁铁矿和钛铁矿间Fe、Mg同位素的分馏机制和控制及影响因素尚不明确。本项目拟在申请人对四川白马层状岩体部分样品已有的Fe同位素研究基础上，利用MC-ICP-MS技术，测定不同岩相带中磁铁矿、钛铁矿、橄榄石和单斜辉石的Fe、Mg同位素组成，阐明基性岩浆演化过程中矿物间Fe、Mg同位素的分馏规律、机制及其关键控制因素。与此同时，借助飞秒激光LA-MC-ICP-MS对磁铁矿和钛铁矿微区的Fe同位素原位分析，深入揭示亚固相线再平衡对二者Fe同位素组成的影响。本项目对进一步完善基性岩浆分离结晶过程中非传统稳定同位素分馏基础理论具有重要意义。

It is paid more and more attentions for geological scientists to study on Fe and Mg isotopes, because Fe and Mg are two major elements and their isotopes can be widely applied to trace numerous geological processes. Recent studies have suggested that the Fe isotope would largely fractionate during mafic magma differentiation, while fractionation of the Mg isotope is very limited. However, the fractionation of Fe and Mg isotopes between minerals in mafic rocks are still poorly understood due to very lack of isotopic compositions of these minerals. Particularly, the mechanisms of Fe and Mg isotopic fractionation between silicate minerals, magnetite and ilmenite, together with the key factors that control these fractionation are not well constrained. On the basis of our preliminary studies on Fe isotope of a small amount of samples from the Baima layered intrusion, Sichuan province, we will use MC-ICP-MS to measure the Fe and Mg isotopic systematics of co-existing magnetite, ilmenite, olivine, and clinopyroxene from all petrographical zones of this intrusion in this project. By doing these analyses, we further attempt to illustrate the regularities, mechanisms and critical control factors of the Fe and Mg isotopic fractionation between minerals during mafic magma differentiation. Meanwhile, we will utilize UV femtosecond LA-MC-ICP-MS to determinate the Fe isotopic variations of the magnetite and ilmenite in-situ, and then to reveal the influencing factors on their Fe isotopes during the process of sub-solidus equilibration on cooling. This project will highlight significantly the fundamental theory of the non-traditional stable isotope fractionation during mafic magma differentiation.