地球科学中铁同位素研究进展

Progress of iron isotope geochemistry in geoscience

21世纪初,铁同位素的高精度分析因多道等离子体质谱仪的引入成为可能。铁在自然界中具有高丰度、多价态和生物可利用性,其同位素地球化学受到广泛关注,并取得巨大的进展。本文综述了铁同位素研究的进展和在地球科学中的应用。这些进展包括:(1)查明了各类陨石的铁同位素组成,并制约了太阳系及早期行星演化过程;(2)调查了地球主要储库的铁同位素组成;(3)积累了大量高、低温常见体系中两相间的铁同位素分馏系数;(4)初步探明了岩浆过程(如部分熔融、地幔交代和岩浆分异等)中的铁同位素分馏行为;(5)初步查明铁同位素在主要低温过程(如风化、早期成岩作用等)中的分馏行为;(6)实例性研究揭示了沉积岩样品铁同位素在示踪古海洋-大气氧逸度变化和早期生命演化方面的潜力。随着人们对铁同位素分馏机制理解的加深,各体系中分馏系数的积累,铁同位素将在地球科学的各个方面得到更广泛的应用。

Iron isotopic ratios cannot be precisely measured until the invention of MC-ICPMS in the beginning of this century. Since then, because of the high abundance and multivalence of iron and also as a bioelement, iron isotope geochemistry has gained an intensive attention from the community. This study summarizes the major progress in iron isotope geochemistry in the last decade as the following. Firstly, iron isotope compositions of most types of meteorites have been reported, which has put constraints on the evolution of the solar system and early planetary differentiation. Secondly, iron isotope compositions have been investigated for the major geological reservoirs. Thirdly, a large number of fractionation factors have been accumulated both for low and high temperature geological processes. Fourthly, iron isotope fractionation behavior in magmatic processes, e. g. , partial melting, mantle metasornatism, magma differentiation, etc. , has been investigated. Fifthly, basic iron isotope fractionation law has been primarily revealed during the major low temperature processes, e. g. , weathering, early diagenesis, etc. Finally, case studies have already revealed the great potential to trace redox condition evolution of paleo-ocean and atmosphere and as a biological signature based on iron isotope records in sedimentary rocks. With the further accumulation of fractionation factors and elucidation of the mechanism of Fe isotope fractionation, Fe isotope geochemistry has the potential to be more widely applied in every aspect of geoscience.