海相沉积氧化还原环境的地球化学识别指标  

Geochemical indices for redox conditions of marine sediments

作　　者：林治家[1] 陈多福[1] 刘芊[1] 

机构地区：[1]中国科学院广州地球化学研究所边缘海地质重点实验室

出　　处：《矿物岩石地球化学通报》2008年第1期72-80,共9页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(40472059);中国科学院知识创新工程重要方向项目(KZCX3-SW-224)和前沿领域项目(GIGCX-04-03)

摘　　要：全球海洋在10～5．4亿年间演变成氧化环境，此后历经多次全球性的缺氧事件后演变到现在的氧化环境。海水和沉积物中多种元素的循环、分异和富集明显受氧化还原条件的影响。Mn、Mo、Cr、V和u等变价元素的溶解度随氧化还原条件的改变产生极大变化，导致沉积物中的元素含量分异；Ni、Co、Cu和Zn等在还原条件下形成硫化物沉淀，导致沉积物中对应元素的富集。这些元素的地球化学行为是古海洋氧化还原条件变化的灵敏指示剂，可以作为恢复古海洋氧化还原环境变化的地球化学指标。黄铁矿化程度（DOP）、生物标志化合物和Ce异常等也是沉积环境氧化还原条件的常用判别指标。泥岩研究中通常采用DOP、U/Th、自生U、V/Cr、Ni/Co和生物标志化合物等指标，碳酸盐岩则主要采用Ce异常指标。当前各种指标的定性分析都取得比较一致的结果，但是用一种或几种定量的地球化学指标来恢复整个古海洋的氧化还原环境目前还有很大的问题。There was a significant oxygenation of deep-ocean waters in the Neoproterozoic era （1～0.54 Ga）. Since then many anoxic events have taken place. The circulation,fractionation and enrichment of many elements in seawater and sediments were obviously influenced by the variation of redox conditions. The large variation of solubility of Mn,Mo,Cr, V and U in seawater, resulted from the variation of redox conditions, could cause the concentration fractionation of these elements in sediments. Some sulfophilic elements, such as Ni, Co,Cu and Zn, could be enriched in sediments as they could be precipitated as sulfide in reduced conditions. Therefore, these elements can be used as sensible geochemical indices for studying the variation of paleo-seawater redox conditions. In addition,the degree of pyritization （DOP）, biomarkers and Ce anomaly of sediments are also common effective geochemistry indices for studying the redox conditions of sedimentary environment. The indices of DOP, U/Th, Uau, V/Cr Ni/Co and biomarkers are usually used to study the redox condition for the formation of mudstones,whereas the Ce anomaly is used to study the redox condition for the formation of carbonate. Although similar results could be obtained by the application of several indices for qualitatively analyzing redox conditions,there is still impossible to quantitatively analyze the redox conditions of the paleo-ocean by using certain one or some quantitative geochemical indices.

关 键 词：沉积岩 氧化还原条件 地球化学指标 

分 类 号：P59[天文地球—地球化学]