摘要
著名的"山西式"铁矿几乎分布于整个华北地区,其成因曾是一个古老的地质问题。本文在前人研究的基础上,通过野外露头观察,并结合镜下鉴定与能谱分析对太原西山七里沟剖面本溪组铁质层中铁质鲕粒结构及其特征进行了详细研究。研究表明,大部分铁质鲕粒具有放射结构,并能隐约看到同心圈层,同时,在鲕粒内部及其周围发现了大量的似蓝细菌丝状体,以及铁质凝块和球粒,具有明显的微生物成因特征。因此,认为铁质鲕粒的形成与微生物密切相关,微生物参与了铁矿的形成。
The “Shangxi-type” iron deposits are well-known for their wide distribution on North China platform. The origins of the deposits including their mineralization processes and the mineral sources, together with their ages, were once concerned by many geologists. Although the geological problems seem clear, the microbial activity is documented to have influence on the formation of the iron deposits just as the Xuanlong iron deposits. The iron deposits outcropped well in Taiyuan Xishan favors our study, and the ferriferous oolites developped in the iron layer of the Benxi Formation at the Qiligou section became our main study object. Through field observation, thin section examination and analysis of Energy spectrum, the composition and texture of the ferriferous oolites are studied in detail. The oolites are matrix-supported, with 45% of ooids and a few other grains （3%） such as bauxite debris and biotic fragments （shell, etc. ） floating in clay minerals. The ooids are well-sorted with the sizes mainly ran- ging from O. 5 mm to 1 mm in diameter. In the thin section, most of the ooids are round, and some rombic and oval- shaped. The cortical layers of the ooids are mainly composed by micritic hematites, whereas the nuclei consist of mic- ritic hematites or clay minerals, which indicate certain common origin between some nuclei and the matrix. Most of the ooids are characterized by radial structure with 2 or 3 obscure concentric layers, which indicate that the ooids probably formed in a relative stable condition, coinciding with the previous conclusion that the iron deposits formed in the restricted lagoon environment. Additionally, abundant intertwined cyanobacteria filaments are found to aggregate around and envelop most of the ooids and the distribution of ferriferous material （ micritic hematites） in the matrix is closely related to these filaments. Spherical cyanobacteria which are intedaid in the intertwined filaments are also rec- ognized under SEM. At the same time, ferriferous clots and pelle
出处
《沉积学报》
CAS
CSCD
北大核心
2013年第3期396-403,共8页
Acta Sedimentologica Sinica
基金
中国石油天然气股份有限公司勘探开发研究院项目<微生物碳酸盐岩与塔里木盆地深部储层的形成研究>(101001cqob52139)
中国石油天然气股份有限公司项目"塔里木盆地碳酸盐岩野外露头储层地质建模研究"(2008D-070602-02)联合资助
关键词
“山西式”铁矿
鲕粒
微生物成因
“Shanxi type” iron deposits
ooids
microbial origin
