中文摘要：

锂同位素在地质学、地球化学研究中有着广阔的应用前景,壳-幔相互作用过程的锂同位素地球化学研究已经成为近年来国际上研究的热点之一。锂同位素在自然界中的变化较大,δ^7Li值为-45‰～＋45‰。锂同位素分析手段目前主要有TIMS、Ion Probe、SIMS、MC-ICPMS等4种技术,其中MC-ICPMS仪器的出现,使锂同位素发展速度明显加快。自然界中很多地质作用过程均能使锂同位素发生分馏。目前,锂同位素已在陨石和宇宙化学、陆壳风化过程、洋壳热液活动及蚀变、板块俯冲及壳幔物质循环、地表水地球化学、卤水来源与演化、热液成矿作用等领域的研究中取得了显著成效,并将成为地球科学中具有巨大应用前景的一种新的地球化学手段。文章对锂同位素在大陆裂谷环境碳酸岩研究中的应用作了较全面介绍,内容包括研究意义、锂含量和锂同位素组成以及取得的主要认识,比如蚀变作用、岩浆分异作用、地壳同化作用和扩散分馏作用均未对碳酸岩、硅酸盐的锂同位素组成造成影响、俯冲作用和地壳循环均没有明显影响地幔的锂同位素组成、地幔温度条件下锂扩散模拟表明地幔中的锂更均一等等。最后简单对比了大陆裂谷环境和碰撞造山环境两类碳酸岩在锂同位素组成上的差别。

英文摘要：

As a useful geochemical tracer,the lithium isotope system has been used to study some important geological or geochemical problems. Recently,the research on Li isotope has become one of the most fast developing fields in the study of crust-mantle interaction. Lithium isotopes show considerable δ^7Li variation in nature from-45‰ to ＋45‰. At present,the analytical methods of lithium isotopic systematics mainly include TIMS,Ion Probe,SIMS and MC-ICPMS,and the advent of MC-ICPMS accelerates their applications in geology. Lithium isotope can be readily fractionated during geological processes in nature. Therefore,the application of lithium isotopic system has significant importance in the fields of meteorolite and cosmochemistry,continental crust weathering process,oceanic crust thermal activity and alteration,continental plate diving and crust-mantle material recycle,surface water geochemistry,halogenic water origin and evolution,and thermal ore mineralization. This technique will thus surely become a useful geochemical tool in the Earth sciences. This paper gives a detailed review of the application of lithium isotopic method to carbonatite in the continental rift environment in the aspects of its scientific value,lithium concentrations and isotopic compositions and the main understanding obtained. It is found that alteration,magmatic differentiation,crustal assimilation and diffusional fractionation have no effects on lithium isotopic compositions of carbonatite and silicate rocks. Modeling of Li diffusion at mantle temperatures suggests that limited δ7Li variation in the mantle with time reflects the more effective homogenization of Li in the mantle,which may also explain the fact why there is little overall deviation of δ7Li values of mantle-derived material from the average mantle value of 4‰±2‰. A comparison of lithium isotopic compositions of carbonatite between the continental rift environment and the collisional orogenic environment is also made in this paper.