Garnet-Spinel Transition in the Upper Mantle: Review and Interpretation  

作　　者：苏本勋 张宏福 Sakyi Patrick Asamoah 秦克章 汤艳杰 英基丰 肖燕 

机构地区：[1]Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences [2]State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences [3]Graduate University of Chinese Academy of Sciences [4]Department of Earth Science, University of Ghana, Legon-Accra, Ghana

出　　处：《Journal of Earth Science》2010年第5期635-640,共6页地球科学学刊（英文版）

基　　金：supported by the Special Research Project of the State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences (No. 1008);the National Natural Science Foundation of China (No. 90714008)

摘　　要：This study carried out a comprehensive review of mantle-derived garnet peridotites on the basis of their garnet-spinel compositional relationships. The P-T estimates of the garnet peridotites of both orogenic and xenolithic derivations confirm previously established two garnet-spinel transition （GST） zones. Results of natural samples and experimental studies of all the garnet peridotites plot below the first GST at low P （〈2 GPa）. The second GST at high P （6-10 GPa）, obtained from the experimental system （MgO-Cr203-SiO2）, was firstly evidenced from natural samples in this study and may imply a challenge to our understanding of Cr-rich and Al-poor mineral phase transition under ultrahigh P condition. Based on the data and our estimates, we propose the existence of another GST within the garnet peridotite discontinuous zone and a potential spinel-phase peridotite zone in the upper mantle.This study carried out a comprehensive review of mantle-derived garnet peridotites on the basis of their garnet-spinel compositional relationships. The P-T estimates of the garnet peridotites of both orogenic and xenolithic derivations confirm previously established two garnet-spinel transition （GST） zones. Results of natural samples and experimental studies of all the garnet peridotites plot below the first GST at low P （〈2 GPa）. The second GST at high P （6-10 GPa）, obtained from the experimental system （MgO-Cr203-SiO2）, was firstly evidenced from natural samples in this study and may imply a challenge to our understanding of Cr-rich and Al-poor mineral phase transition under ultrahigh P condition. Based on the data and our estimates, we propose the existence of another GST within the garnet peridotite discontinuous zone and a potential spinel-phase peridotite zone in the upper mantle.

关 键 词：garnet peridotite garnet-spinel transition spinel peridotite ultra-high P-T upper mantle. 

分 类 号：P583[天文地球—岩石学]