| 王煜,谭先锋,蒋聪,唐远兰,周欢焕,谭东萍,王萍.早期成岩过程中铁元素地球化学循环研究进展[J].地质找矿论丛,2019,34(2):254-264 |
| 早期成岩过程中铁元素地球化学循环研究进展 |
| Advance in study of the iron geochemical cycle during early diagenesis |
| 投稿时间：2018-12-19 |
| DOI：10.6053/j.issn.1001-1412.2019.02.013 |
| 中文关键词: 早期成岩 铁元素 元素地球化学 地球化学循环 环境磁学 |
| 英文关键词:early diagenesis iron geochemistry of element geochemical cycle environmental magnetism |
| 基金项目:国家自然科学基金项目（编号：41202043）、重庆市基础科学与前沿技术项目（编号：2016jcyjA0606）、国家级大学生科技创新项目（编号：201711551001）、重庆市大学生科技创新项目（编号：201811551023）联合资助。 |
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| 中文摘要: |
| 铁是海洋沉积物中重要的氧化还原敏感性元素之一，是早期成岩过程中地球化学循环变化的重要动力因素。早期成岩过程中，表层沉积物中铁氧化物的赋存形态主要可分无定形（弱晶型）铁氧化物和晶型铁氧化物，且前者的含量主要决定着沉积物中铁氧化物的还原活性；铁氧化物可以通过与硫酸盐还原产生的硫化物反应进行还原，还能在铁还原菌的参与下被表层沉积物中的有机质还原，沉积物中活性铁含量、有机质含量、沉积速率、植物根系导氧作用及底栖生物的扰动均能对铁还原率造成影响。早期成岩过程中可以形成黄铁矿，形成机理主要有：1）沉积物中先前形成的硫复铁矿（Fe3S4）等前体物质通过加硫反应形成；2）硫过饱和的球粒胶体通过脱水、成核、结晶以及聚合作用而成单个草莓状黄铁矿或初始自行黄铁矿微晶成核、生长、聚集、固化的小型黄铁矿微球团并入更大的胶体状黄铁矿结核、草莓状黄铁矿分组，从而形成黄铁矿集合体；黄铁矿化度（DOP）可作为区分古海洋氧化还原环境的指标。对铁同位素的研究表明，异化还原作用（DIR）过程中产生的铁同位素值偏低；页岩中黄铁矿的铁同位素在2.3 Ga附近发生的突变反映了第一次大气氧气增高事件。磁学参数对铁相变化具有良好的反应，环境磁学在早期成岩过程研究中的应用，有助于快速划分铁还原带、研究环境中重金属循环行为。 |
| 英文摘要: |
| Iron is one of the most important redox sensitive elements in marine sediments and an important dynamic factor for geochemical cycling during early diagenesis. In the early diagenesis, iron oxides in surface sediments can be divided into amorphous iron oxides and crystalline iron oxides, and the content of the former mainly determines the activity of iron oxides in sediments. Iron oxides can be reduced by reaction with sulfides produced by sulfate reduction, also reduced by organic matter in surface sediments with the participation of iron-reducing bacteria. The content of active iron, the content of organic matter, the deposition rate, the oxygen conduction of plant roots and the disturbance of benthic organisms all affect the iron reduction rate in sediments. In the early diagenesis, pyrite is formed in two ways:① formed by addition of sulfur to the precursors such as greigite (Fe3S4) reaction. ②formed by dehydration, nucleation, crystallization and polymerization of sulfur-supersaturated spheroidal colloids as single framboid pyrite or by nucleation, growth, aggregation, incorporation of small pyrite microspheres into larger colloidal pyrite nodules and grouping of framboid pyrite. Degree of pyritization (DOP) is a significant proxy in distinguishing the redox state of ancient oceans. Studies on iron isotopes shows that the iron isotope in DIR is low, and the abrupt change of iron isotope of pyrite in shale around 2.3 Ga corresponds to the first atmosphere oxygen enrichment event. The application of environmental magnetism in the study of early diagenesis is helpful in distinguishing iron reduction zone in sediments and in studying heavy metal recycling behavior in the environment. |
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