铈同位素研究进展

Advances of cerium isotope researches

铈作为一种重要的稀土元素,广泛存在于各种地质储库,并参与到成岩成矿作用。铈是少数具有可变价态(Ce^(3+),Ce^(4+))的稀土元素,由此导致的铈异常被广泛应用于示踪氧化还原条件变化。随着质谱技术的不断发展,铈同位素的高精度测量得以实现,并在地质测年、示踪氧化还原状态等方面取得了重要进展。本文在前人研究的基础上,对铈同位素的测试方法进行了小结。铈同位素测试主要利用热电离质谱(TIMS)和多接收电感耦合等离子体质谱(MC-ICP-MS)完成,测试精度最高可达到0.02‰(2SD)。随后结合最新的研究成果,较全面的总结了铈同位素在不同地质储库(如天体、海洋等)中的组成特征以及不同环境条件下(如低温、不同pH值等)的分馏机制,指出铈同位素在不同温度体系下的分馏机制仍然缺少模拟实验的验证和理论计算的支持。最后梳理了铈同位素在示踪物质来源、沉积环境以及地质测年等方面的应用,显示了铈同位素具有较大的应用潜力。

Cerium,as an important rare earth element,is present widely in various geological reservoirs and is involved in processes of diagenesis and mineralization.Cerium is one of the few rare earth elements with variable valence states(Ce^(3+),Ce^(4+)),and the cerium anomaly is widely used to trace changes of redox conditions.With the continuous development of mass spectrometry technology,the high precision measurement of cerium isotope has been realized,and some important progresses have been made in fields of geological dating,redox state tracing,and others.Based on the previous studies,the measurement methods of cerium isotope are summarized systematically in this paper.Cerium isotope composition is measured mainly using the Thermal Ionization Mass Spectrometer(TIMS)and Multi-Collector Inductively Coupled Plasma Mass Spectrometry(MC-ICP-MS),with the highest analytical accuracy of 0.02‰(2SD).Then,combined with the latest research results,the compositional characteristics of cerium isotopes of different geological reservoirs(such as celestial bodies,ocean,etc.)and the fractionation mechanisms of cerium isotopes in different environments(such as low temperature,different pH values,etc.)are comprehensively summarized.The fractionation mechanisms of cerium isotopes in different temperature systems are still lack of the verification of simulation experiment and support of theoretical calculation.Finally,the applications of cerium isotopes in tracing material source,tracing sedimentary environment,and the geological dating are summarized.It is shown that the cerium isotope has great application potential in relevant geochemical researches.