铁元素对海相沉积物早期成岩作用的影响

Advances in the Role of Iron in Marine Sediments during Early Diagenesis

铁元素是地壳中丰度最高的元素之一,在海相沉积物成岩过程中起着非常重要的作用。铁元素作为海洋初级生产力的微营养元素,影响海相沉积物中有机质的输入,其在早期成岩阶段与硫化物和磷元素的耦合关系,可以促进或者降低有机质的保存;铁元素在海相沉积物早期成岩过程中可以改变孔隙水的化学性质,影响亚稳定碳酸盐矿物的保存,导致碳酸盐沉积物的溶解与胶结;铁元素在早期成岩过程中赋存状态的改变对海相沉积物的磁学性质有重要的影响,成岩作用可能削弱或者产生二次磁学信号;铁元素在异化铁还原过程中发生同位素分馏,对古海洋中铁的生物地球化学循环过程及古海洋氧化还原状态有重要的指示意义。上述过程与铁元素的赋存状态和有机质分解过程相关,值得进一步深入研究。相关研究对识别地质历史中的缺氧事件、海相烃源岩的形成过程、碳酸盐沉积的模拟以及全球碳循环等一系列重大问题有重要意义。

Iron as one of the highest abundance elements in the crust,plays a very important role in the marine sediment diagenesis.Iron as a nutritive elements in marine primary productivity,affects the input of organic matter in marine sediments;the coupling of iron sulfide and phosphorus can promote or reduce the organic matter burial;During early diagenesis,iron in marine sediments can alter the chemical properties of the pore water,resulting in aragonite grain dissolution,thereby affecting the cementation of carbonate sediments;Diagenetic alterations of iron minerals driven by anaerobic oxidation of organic matter have an important influence on the magnetic properties of marine sediments,producing secondary magnetic signal or weakening them;Isotope fractionation during dissimilatory microbial iron reduction,can indicate the biogeochemical cycle of iron and the redox conditions of ancient oceans.Processes mentioned above relate to the input of terrigenous detrital and the metabolism of organic matter,requiring further studies.These studies will have important significance to the related research,such as Oceanic Anoxic Events,the formation mechanism of marine source rocks and the model of carbonate precipitation and global carbon cycle.