Extremely high Li and low δ7 Li signatures in the lithospheric mantle
作者单位：State Key Laboratory of Lithospheric EvolutionInstitute of Geology and GeophysicsChinese Academy of Sciences Centre National de la Recherche ScientifiqueCRPGBP2054501 Vandoeuvre-Les-Nancy CedexFrance Department of Earth ScienceUniversity of GhanaP.O.Box LG 58Legon-AccraGhana Department of Earth Sciencesthe University of Hong Kong
会议名称：《中国科学院地质与地球物理研究所2012年度（第12届）...》
会议日期：2013年
学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学]
基 金：financially supported by the National Natural Science Foundation of China(Grants 40973012,41173011 and 91014007) the China Postdoctoral Science Foundation to Ben-Xun Su
关 键 词：Li isotope Mantle peridotite xenolith Metasomatism Lithospheric mantle
摘 要：Geochemical behavior of lithium(Li) in mantle processes is generally explained by:(1) Li diffuses into minerals from melts,faster in clinopyroxene than in olivine,creating isotopically lighter-Li clinopyroxene and heavier-Li olivine;(2) Partitioning of Li changes with temperature,and as cooling proceeds Li diffuses into clinopyroxene from olivine,also resulting in low-δLi clinopyroxene and high-δLi olivine,similar to the result of process(1),Our results obtained from highly carbonatite-metasomatized peridotite xenoliths from the Western Qinling reveal that the minerals of these xenoliths contain extremely high Li in a range of 2-16 ppm for olivine,2-43 ppm for orthopyroxene,and up to 75 ppm for ***,olivines have much lower 6’Li(down to - 42‰) relative to co-existent *** observations provide important insights into the behavior of Li during mantle *** explanation is that the fractionation of Li strongly depends on the metasomatic *** melts,particularly Na-rich carbonatitic melts,which have high Li contents(-200 ppm) but mantle levelδLi(3-5‰),tend to effectively transfer Li into olivine and Li into pyroxene,while silicate melts behave on the *** might be the existence of a reservoir with a high Li content but lowδLi,like eclogite,in the mantle since the Li released into the overlying mantle wedge during *** study reveals the disLinctive behavior of Li between the carbonatite and silicate metasomatism in the mantle.