赋存于蛇绿岩中的豆荚状铬铁矿是一种重要的Cr矿床类型，但其成因一直存在较大争议。本项目拟对典型豆荚状铬铁矿床（西藏雅鲁藏布蛇绿岩带东段的罗布莎铬铁矿床和中段的日喀则蛇绿岩体及其矿化）进行系统的Fe、Cr同位素地球化学研究。通过对围岩、矿石及其单矿物进行高精度Fe、Cr同位素测定，查明Fe、Cr同位素在豆荚状铬铁矿及地幔橄榄岩中基本分布特征，并分析引起Fe、Cr同位素变化的控制因素和Fe、Cr同位素分馏机制。结合其他地质地球化学指标，研究Fe、Cr同位素分馏与地幔过程的关系，为进一步揭示豆荚状铬铁矿床成因提供新的制约。

Podiform chromite in ophiolite is an important type of chromium deposits, but the origin of podiform chromite is highly debated. We will investigate systematically the Fe and Cr isotopic compositions of the typical podiform chromite (Luobusha deposit in the eastern and Xigaze mineralization in the middle of Yarlung-Zangbo ophiolite belt, Tibet). It will be obtained the distribution characteristics of Fe and Cr isotopes in the podiform chromites and the mantle peridotites based on high-precision measurements of Fe and Cr isotopes for the ores and the wall rocks and the minerals. In addition, we attempt to reveal the controlling factors for the variations of Fe and Cr isotopes and the mechanisms of Fe and Cr fractionation. Integrated with other geological and geochemical parameters, we try to illustrate the relationships between fractionation of Fe, Cr isotopes and mantle processes, and then to find out the new constraints on formation of podiform chromite deposits.