微生物岩稀土元素恢复古海洋环境的研究综述

沉积岩中的稀土元素组成特征对于解释古海水稀土元素来源和海水地球化学演化有重要意义。海洋无机成因和生物成因的矿物在保存古海水稀土元素信息方面都存在各种问题。由于微生物岩是由微生物的诱导矿化作用形成的, 早期研究认为它是能够记录古海水稀土元素信号最可靠的地质载体之一。但最新研究发现, 成岩作用和陆源碎屑输入也能够引起微生物岩稀土元素组成的变化, 由此可能导致古环境解释出现错误。然而, 非海水控制因素对微生物岩稀土元素组成的影响还不清楚, 也缺乏系统的研究, 这使得微生物岩稀土元素指示古环境的可靠性受到质疑。如何从微生物岩中提取真实可靠的古海水稀土元素信号是研究的主题之一, 这对于解决古海水稀土元素随时间演化的问题, 理解生物与环境的协同演化都具有重要意义。

Review on the research of rare earth elements in microbialites

The composition characteristics of rare earth elements (REE) in ancient sedimentary rocks play an important role in explain-ing the source of REE in palaeoseawater and the geochemical evolution of seawater. Marine inorganic and biogenic minerals have various problems in preserving the information of REE of ancient seawater. Early studies believe that microbialites was the most reliable geological sample that can record REE signals in ancient seawater because of its induced mineralization. However, the latest research has found that diagenesis and terrigenous clastics inputs can cause the fractionation of REE in microbialites, which may bias palaeoenvironmental interpretations. However, the mechanism of non-seawater controlling factors on the fractionation of REE in microbialites is not clear, and there is a lack of systematic research, which leads to questioning the reliability of REE in microbialites to indicate paleoenvironment. How to extract true and reliable ancient sea-water REE signals from microbialites is the main problem in the future research, which is key for solving the major scientific problems of the evolution of REE in ancient seawater over time, and for understanding the co-evolution of biology and envi-ronment in geological history.