古元古代末浅海赤铁矿化微生物席:标识与意义  

Hematized microbial mats thrived in terminal Paleoproterozoic shallow seawaters: identification and implications

作　　者：赵石珂 史晓颖[1,2] 孙龙飞 谢宝增 汤冬杰[1,3] ZHAO Shike;SHI Xiaoying;SUN Longfei;XIE Baozeng;TANG Dongjie(Stale Key Laboralory of Biogeology and Emuironmental Geology,China Unersilty of Gesciences(Beijing),Beijing 100083,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing).Beijing 100083,China;Institute of Earth Sciences,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)生物地质与环境地质国家重点实验室,北京100083 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]中国地质大学(北京)科学研究院,北京100083

出　　处：《古地理学报》2022年第6期1114-1129,共16页Journal of Palaeogeography：Chinese Edition

基　　金：国家自然科学基金项目(Nos.41930320,41972028);中国地质大学(北京)“拔尖青年教师创新能力培养项目”(No.2652019093);中国地质大学(北京)大学生创新创业训练计划项目(No.202111415097)共同支持。

摘　　要：微生物活动导致铁氧化被认为是前寒武纪铁建造和红层形成的重要机制之一,但是地质记录中却鲜有相关证据。针对这一问题,本研究选择华北古元古代末的大红峪组微生物席成因构造(MISS)为研究对象,通过沉积学和矿物学的综合研究,揭示微生物活动在前寒武纪铁循环中的关键作用。研究表明:华北井陉大红峪组发育大量以砂裂为代表的MISS,指示当时潮间带至潮上带广泛发育微生物席;非微生物席层发育大量原位和近距离搬运的海绿石,指示低氧富铁的浅海和孔隙水化学条件,而相邻微生物席层则发生了显著的赤铁矿化,指示相对更氧化的沉积环境。考虑到微生物席层与相邻(厘米级)非微生物席层间微生物活动与矿物组成的明显差异,笔者提出微生物活动可能是导致当时低氧铁化浅海环境局部铁氧化的重要机制。本研究提供了微生物参与Fe离子氧化的重要证据,对揭示前寒武纪红层和大规模铁建造形成机制具有启示意义。Microbially mediated iron oxidation has been considered as one of the most important mechanisms for the formation of Precambrian iron formation and marine red bed. However, the evidence of microbial mediation is rarely recorded through Earth history. To reveal the potential roles of microbes in the Precambrian iron cycling, we chose microbially induced sedimentary structure(MISS)from the late Paleoproterozoic Dahongyu Formation, North China, as target, and conducted a comprehensive investigation in sedimentology and mineralogy. In this formation, sand cracks are the dominated type of MISS,indicating the existence of abundant microbial mats on the intertidal to supratidal zones previously. Microscopic observations show that the non-microbial mat layer contains abundant in situ to shortly transported glauconite, indicating suboxic and iron-rich shallow seawater and porewater chemistry. In contrast, the microbial mats show significant hematization, indicative of more oxygenated conditions. Considering the differences in microbial activity and mineralogy between the microbial mat and adjacent non-microbial mat layers, we propose that microbial mediation is an important mechanism leading to the oxidation of Fe(Ⅱ)in the weakly oxygenated ferruginous shallow seawater. This study provides important evidence for microbial mediation in Fe(Ⅱ)oxidation and may shed light on the formation of Precambrian marine red bed and iron formation.

关 键 词：大红峪组 赤铁矿 海绿石 氧化还原 铁循环 

分 类 号：P534.41[天文地球—古生物学与地层学]