锂同位素地球化学行为综述  

General Description of Geochemical Behavior of Lithium Isotopes

作　　者：陈辉 CHEN Hui(MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Changsha,410083,P.R.China;School of Geosciences and Info-physics,Central South University,Changsha,410083,P.R.China)

机构地区：[1]中南大学地球科学与信息物理学院,湖南长沙410083 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083

出　　处：《南方金属》2023年第6期25-30,共6页Southern Metals

摘　　要：锂(Li)的2个稳定同位素^(6)Li和^(7)Li二者具有较大的相对质量差(约17%)和不同的扩散速率,因此在地质过程中能发生显著分馏,可追溯物质来源和流体地球化学行为。^(6)Li相对易于进入矿物相,^(7)Li倾向于进入流体相中,导致流体中的Li同位素越来越重。同时,随着温度的降低锂同位素的分馏程度增大。由于二者的质量差异,^(6)Li比^(7)Li的扩散速率快。在风化过程中,风化作用越强,锂同位素分馏越显著。不同的锂同位素可指示不同的风化层物质。俯冲作用中,高δ^(7)Li值流体交代上覆地幔,可导致与俯冲板片相邻的地幔锂同位素组成变重。锂同位素的分馏不受花岗岩分异结晶的影响,而只在低温伟晶岩中存在较大锂同位素分馏。The two stable isotopes of lithium(Li),^(6)Li and ^(7)Li,have large relative mass differences(~17%)and different diffusion rates,and thus can undergo significant fractionation during geological processes that can trace the origin and fluid geochemical behavior of the material.^(6)Li is relatively easy to enter the mineral phase,and ^(7)Li tends to enter the fluid phase,resulting in increasingly heavier Li isotopes in the fluid.Meanwhile,the fractionation of lithium isotopes increases with decreasing temperature.Due to the mass difference between the two,^(6)Li has a faster diffusion rate than ^(7)Li.In the weathering process,the stronger the weathering,the more significant the lithium isotope fractionation.Different lithium isotopes can indicate different weathering layer materials.In the subduction,the high δ^(7)Li value fluid accounts for the overlying mantle,which can lead to the heavier lithium isotope composition of the mantle adjacent to the subducted slab.Lithium isotope fractionation is not affected by granite fractionation crystallization,but only in low-temperature pegmatites with large lithium isotope fractionation.

关 键 词：锂同位素 分馏 风化作用 俯冲过程 

分 类 号：P597[天文地球—地球化学]