海相碳酸盐岩稀土元素在古环境研究中的应用

Application of Rare Earth Elements of the Marine Carbonate Rocks in Paleoenvironmental Researches

海相碳酸盐岩稀土元素(REE)配分模式和含量比值在古海洋环境研究中发挥着重要的作用。尽管海相碳酸盐岩REE主要来源于海水,但是也可能受到陆源碎屑输入和后期成岩改造的影响,因此需要对获得的REE可靠性进行全面评估。与此同时,选取合适的分析方法对获得可靠的碳酸盐相REE含量至关重要。对碳酸盐岩REE的地球化学性质、化学分析与数据处理方法、可行性验证及古环境应用方面进行总结与展望。在未来工作中,应着重于建立更加完善的分析方法,结合宏观地质背景、微观岩相学特征、其他地球化学指标以及同期沉积页岩的REE信息,开展海相碳酸盐岩REE在古海洋环境的全球表现形式研究。

The pattern,contents and ratios of Rare Earth Elements（ REE） from marine carbonates play an important role in the paleo-environmental researches. As result of the REE＇s source being variable,which includes marine carbonates,detrital input and diagenesis,the overall assessment for the reliability of REE＇s data is necessary. Furthermore,appropriate analytical method is vital for the reliable contents of REE. This paper reviewed the geochemical properties,analytical and data processing methods,feasibility verification and paleo-environmental application of carbonates REE. The patterns of REE,which provide theoretical basis for the provenance and depositional environment of carbonates,are various with different sources. Cerium,as a redox sensitive element,is a key proxy for the reconstruction of paleo-redox conditions. There are two available analytical methods,acid-leaching method and direct LA-ICP-MS analytical method,to extract REE of seawater preserved in marine carbonate rocks.The contamination from detritus and diagenetic alteration can be detected by the correlations of various elements or element ratios. The REE of marine carbonate has been well applied to reconstruct the environment changes during the Precambrian,Permian-Triassic transition and Cenozoic.