海洋环境Fe同位素地球化学研究进展

Fe是海洋“生物泵”中限制浮游生物生长和控制海洋初级生产力的主要因素之一，也可间接影响大气中CO2含量，反馈于全球的气候变化。近年来基于多接收电感耦合等离子体质谱仪(MC ICP MS)分析方法的改进及测试精度的提高，应用Fe同位素组成、变化及其分馏机制，为研究海水中Fe的主要来源以及示踪海洋环境中Fe的循环过程等，提供了一个有效地球化学指标，也对示踪地球不同演化阶段的海洋沉积环境变化具有指示意义。较为详细地介绍了海洋环境中不同储库的Fe同位素组成，洋中脊热液流体—玄武岩、海水—大洋玄武岩等水—岩反应影响Fe同位素分馏效应的主要因素及地球不同演化阶段古海洋沉积环境中的Fe同位素变化。认为海洋环境下Fe同位素可以产生较为明显的分馏作用，轻铁同位素具有更易活动、易迁移的特征，并进一步提出不同相态、不同矿物间Fe同位素分馏系数的确定等相关问题仍是今后Fe同位素研究的主要方向。

Advances on Fe Isotope Geochemistry in Marine Environments

The chemistry of iron in the oceans plays an important role in controlling primary production and serves a limited micronutrient element for planktons in "biological pump",and consequently Fe is corresponding potential for regulating global climate by fertilizing the ocean and drawing down atmospheric CO_(2).In recent years,the development in multi-collector inductively coupled plasma mass spectrometry(MC-ICP-MS) have improved precision for iron isotope measurements,and therefore both the isotope composition of iron and isotope fractionation effects have been proved useful in tracing the processes that control inputs and outputs of Fe in the ocean and paleoceanographic evolution.This review summarizes our present knowledge of iron isotope geochemistry which documents the Fe isotope composition in various Fe reservoirs of marine systems,and the main Fe isotope fractionations produced by reaction between hydrothermal fluids and mid-ocean basalts and between seawater and submarine basalts,and the Fe isotope composition in various stages of ancient marine sedimentary environments.Furthermore,our review shows that Fe isotope occur significant fractionation in marine systems and light Fe isotope have higher removal activity than heavy Fe isotope.Finally,we highlight the fact that determining the Fe isotope fractionation factor among various mineral,various phases and during biochemical cycling will be an important future avenue of research,which will bear on our understanding of isotopic variations of Fe in both ancient and modern marine sedimentary environments.