铀“稳定”同位素分馏及其在地球科学中的应用  

Uranium “Stable” Isotope Fractionation and Its Applications in Earth Science

作　　者：梁正伟 田世洪 Liang Zhengwei;Tian Shihong(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013

出　　处：《地球科学》2021年第12期4405-4426,共22页Earth Science

基　　金：东华理工大学博士启动基金(No.DHBK2019292);东华理工大学高层次人才引进配套经费(No.1410000874);国家自然科学基金(No.41773014);江西省“双千计划”创新领军人才长期项目。

摘　　要：铀"稳定"同位素(^(238)U/^(235)U,通常记为δ^(238)U)目前已经成为非传统稳定同位素领域的研究热点.20世纪人们曾经认为铀同位素不存在分馏,因而铀同位素研究发展缓慢.然而随着分析技术的发展,人们发现自然界中铀同位素^(238)U和^(235)U存在显著的分馏,可以作为良好的示踪工具.迄今为止,已经有大量铀同位素作为古氧化还原指标的研究发表,比如用铀同位素示踪地球近地表环境氧含量随时间的演化以及生物大灭绝与海洋氧化还原状态之间的潜在关系.尽管铀同位素在水圈和生物圈协同演化领域取得了丰硕的研究成果,但仍有不少问题亟待深入解决.例如,生物和非生物还原高价铀的微观反应过程对铀同位素分馏的影响,以及铀同位素如何示踪铀矿物质来源等.系统总结了铀同位素地球化学最近十年的研究进展,希望将来铀同位素在铀多金属矿床成因和高温地球化学领域能有所突破.Uranium isotope(^(238)U/^(235)U,usually expressed asδ^(238)U)has been the research hotspot in the field of non-traditional stable isotopes.In the last century,it was thought that uranium isotope fractionation did not exist,so the development of uranium isotope research was very slow.However,with the development of the analytical technology,it has been found that there exists significant fractionation between ^(238)U and ^(235)U in nature,which makes uranium isotopes an ideal tracer in Earth science.Indeed,overwhelming amounts of studies of uranium isotopes as a paleo-redox proxy have been published so far,most of which use uranium isotope to track the evolution of oxygen levels of Earth’s subaerial environments through time and,furthermore,the potential relationship between the several big mass extinctions and the redox conditions of the oceans.Although researches on uranium isotope have achieved progresses in the co-evolution of the hydrosphere and biosphere,some problems still remain some unsolved.For example,the effects of microcosmic pathways of biological and abiotic reduction reactions on uranium isotope fractionation,and how the 238U/235U can trace the source of uranium ore deposits.Here,in this paper,it provides an overview of the uranium and its isotope geochemistry over the last decades,aiming at promoting applications of uranium isotopes in the genesis of uranium polymetallic deposits and high-temperature geochemistry in the future.

关 键 词：铀同位素 分馏机理 示踪 氧含量 生物灭绝 氧化还原状态 铀矿 地球化学 

分 类 号：P597.2[天文地球—地球化学]