Obnazhennaya金伯利岩管中橄榄岩包体的特征—对西伯利亚地幔柱交代作用的启示

This project will investigate mantle plume metasomatism, by focusing on variation of craton lithospheric mantle before and after mantle plume . We will select peridotite entrained in the Obnazhennaya kimberlite (160 Ma) from the Siberian Craton. Based on the limited data of this area, detailed petrology and geochemisty of peridotite xenoliths, especially the harzburgite will be studied. The character and later reformation of Sibrian Craton lithospheric mantle will be constrained through whole-rock Re-Os and minerals Lu-Hf, Rb-Sr and Sm-Nd isotopes. Comparing with the lithospheric mantle character in 360 Ma, we will discuss whether the Siberian Craton lithosphere were reformed by Siberian mantle plume (250 Ma) metasomatism. After that, the metasomatism reformation process of Siberian manlte plume active on craton lithospheric mantle will be revealed.

本项目拟对地幔柱交代作用开展详细的研究。确定地幔柱活动前后克拉通岩石圈地幔的变化是地幔柱交代作用研究的核心问题。本项目拟选择西伯利亚160 Ma 的Obnazhennaya金伯利岩管中橄榄岩包体为研究对象，结合该地区的有限工作，细致研究该地区橄榄岩包体，尤其是方辉橄榄岩的岩石学和地球化学特征。通过全岩的Re-Os及单矿物Lu-Hf、Rb-Sr和Sm-Nd同位素的研究，确定该时期西伯利亚克拉通岩石圈地幔的特征。与360 Ma岩石圈地幔特征对比，讨论西伯利亚克拉通岩石圈是否受到了地幔柱（250 Ma）的交代作用改造，进而揭示西伯利亚地幔柱活动对克拉通岩石圈的交代作用改造过程。

本项目选取西伯利亚雅库特地区的金伯利岩和Obnazhennaya金伯利岩中的橄榄岩包体为研究对象，详细的室内矿物学、岩石学和地球化学研究确定了Obnazhennaya之下的岩石圈地幔难熔与饱满共存；通过全岩的Re-Os同位素与PGE分析，确定了难熔的橄榄岩为古老的岩石圈地幔残留，饱满的橄榄岩是古老岩石圈地幔经历后期熔体改造的结果；通过对金伯利岩中锆石巨晶的分析，确定了西伯利亚雅库特地区金伯利岩形成时代、锆石巨晶的成因和年龄意义，进一步探讨了西伯利亚岩石圈地幔的演化和地幔柱对西伯利亚克拉通岩石圈地幔的影响。