早前寒武纪BIF原生矿物组成及演化、沉积相模式研究进展  

Primary Mineral Information and Depositional Models of Relevant Mineral Facies of the Early Precambrian BIF—A Preliminary Review

作　　者：佟小雪 王长乐[1,2,3] 彭自栋[1,2,3] 南景博 黄华 张连昌 Tong Xiaoxue;Wang Changle;Peng Zidong;Nan Jingbo;Huang Hua;Zhang Lianchang(Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;Institutes of Earth Science, Chinese Academy of Sciences, Beijing 100029, China;University of Chinese Academy of Sciences, Beijing 100049, China;Laboratory of Deep Sea Geology and Geochemistry, Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Hainan Sanya 572000, China;Institute of Mineral Resources Research, China Metallurgical Geology Bureau,Beijing 101300 , China)

机构地区：[1]中国科学院矿产资源研究重点实验室,中国科学院地质与地球物理研究所,北京100029 [2]中国科学院地球科学研究院(筹),北京100029 [3]中国科学院大学,北京100049 [4]深海地质与地球化学研究室,中国科学院深海科学与工程研究所,海南三亚572000 [5]中国冶金地质总局矿产资源研究院,北京101300

出　　处：《地球科学进展》2018年第2期152-165,共14页Advances in Earth Science

基　　金：国家自然科学基金项目“晚太古代清原绿岩带BIF与VMS矿床的成因联系及沉积环境”(编号：41572076);国家自然科学基金青年科学基金项目“霍邱李老庄BIF矿区磁铁矿-菱镁矿组合成因机制研究”(编号：41602097)资助.

摘　　要：条带状铁建造(BIF)原生矿物组成有助于约束其沉积相和沉积环境,当前主要认为三价铁氢氧化物或铁硅酸盐微粒(主要成分为铁蛇纹石或黑硬绿泥石)可能是BIF原生矿物的主要成分,在后期成岩或变质作用过程中转变为赤铁矿、磁铁矿、菱铁矿等矿物。根据BIF的矿物组合可将其沉积相划分为氧化物相、硅酸盐相和碳酸盐相。通过沉积地层学和地球化学等方法研究,以古元古代大氧化事件为标志将沉积相总结为"缺氧还原"和"分层海洋"2种相模式:大氧化事件前,古海洋整体处于缺氧还原环境,BIF沉积相从远岸到近岸呈赤铁矿相—磁铁矿相—碳酸盐相分布,如南非West Rand群BIF(2.96~2.78 Ga)和Kuruman BIF(约2.46 Ga);大氧化事件期间及之后,古海洋上部氧化、下部还原,BIF沉积相与之前截然相反,从远岸到近岸呈碳酸盐相—磁铁矿相—赤铁矿相分布,如中国袁家村BIF(2.2~2.3 Ga)和加拿大Sokoman铁建造(约1.88 Ga)。总体看来,只有特定的沉积环境才能形成这种特殊的地质历史上不再重复出现的沉积建造,而原生矿物组成的甄别和推导、沉积相的形成机制、BIF沉淀条件的准确限定和微生物活动与BIF的关联等问题是推测古海洋环境的关键所在,也是目前亟待解决的问题。The primary mineral compositions of BIF are regarded as ferric oxyhydroxide or iron silicate nanoparticles （mainly greenalite and stilpnomelane ） whichcan transform into minerals like hematite, magnetite and sid- erite. On the basis of predominant iron minerals, three distinctive sedimentary facies are recognized in BIF： oxide facies, silicate facies and carbonate facies. Marked by the Great Oxidation Event （GOE, 2.4-2.2 Ga）, sedimentary facies can be divided into two models： ＂anoxic and reducing＂ model and ＂stratified ocean＂ model. The ancient ocean was anoxic and reducing before GOE, and under this circumstance, BIF was distributed from the distal to proximal zones transforming from hematite facies through magnetite facies to carbonate facies, such as West Rand Group BIF （2.96-2.78 Ga） and Kuruman BIF （ -2.46 Ga） in south Africa. However, the ancient ocean was a stratified ocean during and after GOE, which means that shallow seawater was oxidizing while deeper seawater was reducing, leading to an opposite sedimentary facies distribution compared to the former one： BIF was distributed from the distal to proximal zones transforming from carbonate facies through magnetite facies to hematite facies, such as Yuanjiacun BIF in China （ -2.3 Ga） and Sokoman iron formation in Canada （ - 1.88 Ga）. Overall, BIF is an unrepeatable formation in geological history, which can only form in specific sedimentary environment. The key point to speculate the paleo-ocean environment, namely the problems to be solved at the moment, is to identify and derive the primary mineral compositions, to make sure the genetic mechanism of sedimentary facies especially sili- cate facies, to restrict the sedimentary conditions and to study microbial activities contacting with BIF.

关 键 词：条带状铁建造 矿物成因 原生矿物 沉积相模式 

分 类 号：P618.31[天文地球—矿床学]