海洋沉积物早期成岩作用研究进展  

Research Progress on Geochemical Behavior of Minerals and Elements in Early Diagenesis of Marine Sediments

作　　者：董宏坤 万世明[1,3] 刘喜停 DONG HongKun;WAN ShiMing;LIU XiTing(Key laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Science,Qingdao,Shandong 266071,China;University of Chinese Academy of Science,Beijing 100049,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266061,China;College of Marine Geosciences,Key Laboratory of Submarine Geosciences and Prospecting Technology,Ocean University of China,Qingdao,Shandong 266100,China)

机构地区：[1]中国科学院海洋研究所,中国科学院海洋地质与环境重点实验室,山东青岛266071 [2]中国科学院大学,北京100049 [3]青岛海洋科学与技术国家实验室海洋地质过程与环境功能实验室,山东青岛266061 [4]中国海洋大学海洋地球科学学院,海底科学与探测技术教育部重点实验室,山东青岛266100

出　　处：《沉积学报》2022年第5期1172-1187,共16页Acta Sedimentologica Sinica

基　　金：国家自然科学基金(42076052);中国科学院(B类)战略性科技先导专项(XDB40010100);泰山学者和鳌山人才计划(2017ASTCP-ES01)。

摘　　要：海洋沉积物的早期成岩作用是其沉积和埋藏过程中发生的一系列生物、物理和化学变化,其驱动力为有机质的降解,根据反应自由能大小,参与反应的氧化剂顺序为:O_(2)>NO_(3)^(-)>Mn^(4+)>Fe^(3+)>SO_(4)^(2-)。随着埋深增加,形成一系列氧化—还原化学带,并推动着海底沉积物中部分自生矿物的生成及C、N、S、Fe、Mn等元素的地球化学循环和同位素分馏。一系列有机质降解反应会改变原生沉积物中保存的地球化学信息,对古环境和古气候的研究具有重要意义。在早期成岩作用过程中,有机质降解产生的碳酸根离子和钙离子、亚铁离子结合会形成方解石、文石、菱铁矿等碳酸盐矿物。硫酸盐还原产生的还原态硫最终与亚铁离子形成黄铁矿。此外,目前常用于氧化还原环境重建的代用指标有:1)Fe组分;2)C_(org)/P比值;3)氧化还原敏感微量元素;4)Mo、U同位素。围绕海洋沉积物早期成岩作用中的矿物和元素地球化学行为,评述了早期成岩作用过程中有机质降解反应机制,探讨了反应进程中发生的元素地球化学循环和同位素分馏,以及相伴生的碳酸盐矿物和黄铁矿等自生矿物的形成机理。最后,总结了现有研究的不足,并对未来的研究方向进行了展望。The early diagenesis of marine sediments is a series of biological,physical and chemical changes during the process of their deposition and burial.The driving force is the degradation of organic matter.According to the free energy of reaction,the order of oxidants involved in the reaction is O_(2)>NO_(3)^(-)>Mn^(4+)>Fe^(3+)>SO_(4)^(2-).With increasing buri⁃al depth,a series of redox chemical zones are formed,which promote the formation of some authigenic minerals and the geochemical cycle and isotopic fractionation of C,N,S,Fe,Mn,etc.The series of organic matter degradation reactions change the geochemical information preserved in primary sediments,which is of great significance to the study of paleoenvironment and paleoclimate.In early diagenesis,carbonate ions produced by organic matter degrada⁃tion combine with calcium and ferrous ions to form carbonate minerals(e.g.,calcite,aragonite and siderite).The reduced sulfur produced by sulfate reduction finally forms pyrite with ferrous iron.In addition,four surrogate indices commonly used in redox environment reconstruction are summarized:(1)Fe component;(2)C_(org)/P ratio;(3)redoxsensitive trace elements;(4)Mo and U isotopes.The mechanism of organic matter degradation during the early dia⁃genesis is reviewed based on the geochemical behavior of minerals and elements in the early diagenesis of marine sed⁃iments.The geochemical cycle and isotopic fractionation of elements in the reaction process,and the formation mech⁃anisms of accompanying authigenic minerals such as carbonate minerals and pyrite,are discussed.Finally,the short⁃comings of the existing research and future research directions are discussed.

关 键 词：海洋沉积 早期成岩 有机质降解 自生矿物 同位素分馏 氧化还原重建 

分 类 号：P736.21[天文地球—海洋地质]