湖相原生白云石的微生物成因机理探讨

发布时间：2018-04-23 07:37

本文选题：原生白云石 + 微生物成因　；参考：《古地理学报》2017年02期

【摘要】：近年来,随着对微生物白云石模式研究的不断深入,为解释"白云石问题"提供了新思路。前人对微生物白云石成因研究侧重于微生物对未固结沉积物的改造,即有机准同生白云石化作用,这与实验室中以微生物为媒介形成的"有机原生白云石"在成因机理上存在差异。笔者将微生物白云石机理引入湖相原生白云石成因解释中,认为在湖水—沉积物交界处也会发生微生物成因的原生白云石沉淀,即有机原生白云石。湖水与沉积物交界处的微环境存在明显区别,总体可分为有氧和缺氧2种亚环境,不同亚环境中生活有不同的微生物群落。根据湖泊亚环境特性和微生物种类及其在白云石形成过程中所发挥的作用,可以区分出细菌有氧氧化模式、硫酸盐还原模式和产甲烷模式3种微生物白云石模式。不同模式对应于不同的湖泊环境:细菌有氧氧化模式主要发生于有氧、高Mg/Ca值的咸水/盐湖环境;硫酸盐还原模式主要发生于缺氧、高Mg/Ca值的咸水/盐湖环境;产甲烷模式主要发生于缺氧、低Mg/Ca值的淡水/咸水湖环境。另外,还探讨了pH值变化、SO_4~(2-)的存在和硫化物对镁水合物脱水的影响以及微生物白云石沉淀的环境因子。对微生物成因的原生白云石模式的深入认识,将为湖相白云石成因研究提供新的理论基础和研究思路。
[Abstract]:In recent years, with the development of microorganism dolomite model, it provides a new way to explain dolomite problem. Previous studies on the genesis of microbial dolomite focus on the transformation of unconsolidated sediments by microbes, i.e., organic quasi-syngeneic dolomitization, This is different from the organic primary dolomite formed by microorganism in laboratory. The mechanism of microorganism dolomite is introduced into the explanation of the origin of lacustrine primary dolomite, and it is considered that the primary dolomite precipitate of microbial origin will also occur at the boundary between lake water and sediment, that is, organic primary dolomite. The microenvironment at the junction of lake water and sediment is obviously different. It can be divided into two subenvironments: aerobic and anoxic. There are different microbial communities in different subenvironments. According to the subenvironmental characteristics of the lake and the types of microbes and their role in the formation of dolomite, three microbial dolomite models can be distinguished: aerobic oxidation model, sulfate reduction model and methanogenic model. Different models correspond to different lake environments: bacterial aerobic oxidation occurs mainly in aerobic, salt water / salt lake environment with high Mg/Ca value, sulfate reduction model mainly occurs in salt water / salt lake environment with anoxic and high Mg/Ca values. Methanogenic patterns mainly occur in freshwater / salt lake environments with low Mg/Ca and hypoxia. In addition, the existence of pH value and the effect of sulfides on the dehydration of magnesium hydrate and the environmental factors of microbial dolomite precipitation were also discussed. A deep understanding of the primary dolomite model of microbial origin will provide a new theoretical basis and research idea for the study of lacustrine dolomite genesis.
【作者单位】：北京大学地球与空间科学学院/石油与天然气研究中心;中国地质大学(北京)地球科学与资源学院;
【基金】：国家自然科学基金项目(批准号:41572117)资助~~
【分类号】：P578.6

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