Kaapvaal-Siberian克拉通石榴橄榄岩的镁-铁同位素

地幔是硅酸盐地球最大的Mg－Fe储库，地幔的Mg－Fe同位素组成对我们研究地球的形成和演化以及高温地质过程中Mg-Fe的分馏行为至关重要。新鲜的橄榄岩捕掳体是被深源岩浆携带至地表的地幔直接样品，因此是研究地幔Mg-Fe同位素的重要对象。目前文献中所发表的Mg同位素数据主要是以浅部的尖晶石相橄榄岩来代表上地幔（<60km）的平均Mg同位素组成，而对来自更深部地幔的石榴石橄榄岩的Mg-Fe同位素组成几乎没有研究。因此尚不清楚浅部和深部地幔的平均Mg-Fe同位素组成是否存在显著差异，这制约了对全硅酸盐地球（BSE）Mg-Fe同位素组成的限定。.本项目拟测量Kaapvaal和Siberian克拉通的20个石榴石二辉橄榄岩和方辉橄榄岩全岩及共存29个单矿物的Mg-Fe同位素组成。此研究将提供目前文献中非常欠缺的> 60km上地幔的Mg-Fe同位素组成，有助于我们更好地理解高温下矿物之间的同位素分馏机制。

The mantle is the Bulk Silicate Earth’s largest Mg and Fe reservoirs. Studies of the Mg and Fe isotopic compositions of the mantle are important for understanding its geochemistry and the accretion history of the Earh as well as the behaviors of inter-mineral fractionation for both Mg and Fe during high-temperature geological processes. Peridotite xenoliths brought up by deeply formed magmas such as kimberlites and continental basalts provide important probes to study the vertical sections of the sub-continental lithospheric mantle (SCLM). The Mg isotope studies have mainly focused on the fertile upper mantle represented by peridotites from the spinel facies (<60 km). Rather fewer data on the Mg isotopic compositions of garnet peridotites from the deeper portions of the upper mantle exist in the literature, and there is yet no study on the inter-mineral Mg isotopic fractionations between coexisting mantle minerals from these peridotites with deep provenances. The Mg and Fe isotopic compositions of the bulk silicate Earth (BSE) and the mechanisms governing Mg and Fe isotopic fractionations in the mantle are not fully resolved. .In this project, we plan to present combined Mg and Fe isotopic data of whole-rocks and mineral separates in well-characterized garnet lherzolites and harzburgites from the Kaapvaal and Siberian Cratons. The major objective of this project is to outline the Mg and Fe isotopic compositions of mantle rocks equilibrated at greater depths to broaden our understanding of compositions and evolution in the deep upper mantle represented by peridotites from the garnet stability field.