地质历史时期海洋Li同位素演变

Marine lithium isotope evolution during geological history

Li是一种碱金属元素,由于它不受氧化还原和生物效应的影响,因此在追踪地球元素循环方面非常有利。并且Li在海洋中的留存时间远大于海水混合时间,因此海洋中的Li具有相对均一的组成,从而能够代表对应地质历史时期整体海洋情况。近年来海洋Li同位素被应用在示踪大陆风化模式领域,并取得了很多成果。笔者等在系统总结全球海洋Li循环作用和表生地质作用的Li同位素分馏机制的基础上,通过收集并整理、估算了不同时期海洋Li同位素组成,对地质历史时期海洋Li同位素组成变化与改变大陆风化模式相关的地质事件进行分析,再结合同时期碳酸盐岩C、Sr同位素数据进行对比分析,探讨Li、C、Sr同位素演化与地质事件之间的关系。最后,讨论了目前海洋Li同位素组成方面研究的不足,为后续利用海洋Li同位素记录示踪大陆风化模式的应用提供了参考。

Li is an alkali metal element.Since it is not affected by redox and biological effects,it is very beneficial in tracking the earth’s element cycling.Moreover,the retention time of Li in the ocean is much longer than the mixing time of seawater,so Li in the ocean has a relatively uniform composition,which can represent the overall ocean situation in the corresponding geological history.In recent years,Li isotope in marine have been used to trace continental weathering process,and many achievements have been made.On the basis of systematically summarizing the Li isotope fractionation mechanism of global marine Li cycling and supergene geological processes,this paper collects,collates and estimates the marine Li isotope composition in different periods,and analyzes the geological events related to changes in marine Li isotope composition and changes in continental weathering patterns during geological history.Then,the C and Sr isotope data of carbonate rocks in the contract period are compared and analyzed to discuss the relationship between Li,C,Sr isotope evolution and geological events.Finally,the deficiencies in the current study of marine Li isotope composition are discussed,which provides a reference for the follow-up application of marine Li isotope records to trace continental weathering models.