钙同位素在古海洋研究中的应用及进展

Application and Research Progress of Calcium Isotopes in Paleoceanography:A review

【意义】钙(Ca)是重要的造岩元素和生命必需元素,广泛参与地球表层物质循环过程,并记录着海洋环境及其演化。钙同位素在地球表层无机和有机作用过程中可发生不同程度的分馏,对于研究海洋钙循环和地球表层圈层相互作用具有重要价值。伴随着相关分析测试技术的进步,钙同位素日益成为重要的地球化学研究手段。鉴于钙同位素近年来在古海洋研究领域的广泛应用,有必要对其进行综述。【方法】以前人文献资料为基础,系统地介绍了钙同位素的基本原理、分馏机理、海洋钙循环及其同位素特征等方面的研究进展,进一步对其在碳酸盐岩成岩作用评估、深时海水钙同位素组成厘定、海洋钙循环重建等领域的应用进行了介绍和探讨,并对钙同位素在古海洋领域的发展方向进行了展望,以期促进深时钙循环研究。【结论和展望】钙同位素作为研究海洋钙循环的一把钥匙,日益成为一种重要的研究手段。目前,对钙同位素在不同矿物体系中的分馏机理已建立基础的认识,海洋钙源—汇通量及其钙同位素组成也得到初步的厘定。未来可进一步优化钙同位素分析测试方法,完善钙同位素分馏理论与深时海水钙同位素演化曲线,加强对古今海洋钙循环源—汇通量、钙同位素特征及其影响因素的多指标和定量化研究,提升对钙地球化学循环过程的认识。

[Significance]Calcium(Ca)is a major rock-forming and biological nutrient element,which actively par-ticipates in geochemical cycling processes of the Earth’s surface,recording the marine environment and its evolution.Owing to various degrees of fractionation by inorganic and organic processes in Earth's surface environment,calcium isotopes are a powerful tool for tracing marine calcium cycle and interactions between Spheres of the Earth.With the development of analysis techniques,calcium isotopes have become an important research method in the field of geo-chemistry.Given the extensive application of calcium isotopes in paleoceanography,it is necessary to provide a re-view.[Methods]On the basis of previous literature,this comprehensive review first introduced the fundamental prin-ciples and fractionation mechanisms of calcium isotopes,the features of the marine calcium cycle,and its isotopes.Based on the current research progress and trend,the main applications of calcium isotopes for paleoceanography,in-cluding the evaluation of carbonate diagenesis,the determination of seawater calcium isotope compositions,and the reconstruction of marine calcium cycle in deep time,are further summarized.Finally,suggestions for the future de-velopment of calcium isotopes in the field of paleoceanography are proposed,which might help promote studies on the deep-time calcium cycle.[Conclusions and Prospects]As a key in researching marine calcium cycle,calcium iso-topes gradually become an important tool.Knowledge of calcium isotopic fractionation mechanisms for different miner-al systems is established preliminary.Fluxes of marine calcium sources and sinks and their calcium isotopic composi-tions are determined roughly.In the future,it would be effective to enhance the understanding of calcium cycle by im-proving the measurement and analysis technology,optimizing theories of calcium isotopic fractionation mechanisms and calcium isotopic evolution curve of seawater in deep time,and conducting multi-proxy and quantitative research about the change of fluxes,calcium isotopic compositions and controlling factors for different calcium sources and sinks.