Geochemical constraints on the genesis of the Ekou banded iron formation, Shanxi Province, North China
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ORIGINAL PAPER
Geochemical constraints on the genesis of the Ekou banded iron formation, Shanxi Province, North China Yekai Men1 · Ende Wang2 · Jianfei Fu2 · Sanshi Jia1 · Xinwei You2 · Qiangwen He3 Received: 22 January 2020 / Accepted: 20 September 2020 © Geologische Vereinigung e.V. (GV) 2020
Abstract The Ekou banded iron formation (BIF) in the Wutai area is hosted within the late Archean Baizhiyan formation. The mineral assemblage is used to identify oxide and silicate facies. The oxide facies is composed of magnetite and quartz, and the silicate facies is characterized by the presence of silicate minerals. A geochemical analysis shows that the major elemental compositions are dominantly S iO2 and Fe2O3T, with very little Al2O3 and TiO2 and minor abundances of incompatible elements and transition elements. These results indicate that negligible terrigenous materials were involved in the BIF deposition. The rare-earth elements (REEs), normalized by post-Archean Australian shale, exhibit the characteristics of light REE (LREE) depletion, heavy REE (HREE) enrichment, and positive La, Y, and Eu anomalies. The Y/Ho ratios are superchondritic. These results indicate that the material that formed the Ekou BIF originated from the mixing of seawater and submarine hydrothermal fluids. A Ce anomaly deficiency and heavy Fe isotope enrichment indicate that the Ekou BIF formed in an anoxic marine environment. The δ30SiNBS-28 values for quartz in the Ekou BIF are similar to those of other BIFs with distribution ranges of modern sinters and black smokers. The δ18OV-SMOW distribution is similar to that of hydrothermal sedimentary siliceous rocks. These results suggest that the formation of the Ekou BIF was closely connected to submarine volcanic exhalation activity. Keywords Banded iron formation · Wutai area · Anoxic marine environment · Submarine exhalative sedimentation
Introduction The term banded iron formation (BIF) typically refers to marine chemical sedimentary rocks unique to the early Precambrian, and these BIFs have a total iron (Fe) content above 15% and are mainly composed of interbedded silicon (Si) and iron bands (James 1954). The precursor BIFs are upgraded to Fe ores, wherein the Fe content of > 60% by weight results from the multistage, sequential removal of silicon from the host by supergene, hypogene, or hydrothermal fluids (Taylor 2001). The BIF-type Fe deposit is the most important type of iron deposit and accounts for * Yekai Men [email protected] 1
School of Resource and Materials, Northeastern University at Qinhuangdao, Qinhuangdao, China
2
School of Resources and Civil Engineering, Northeastern University, Shenyang, China
3
Beijing Urban Construction Exploration and Surveying Design Research Institute CO., LTD, Beijing, China
approximately 90% of iron ore produced worldwide (Isley 1995). BIFs are considered to be products of special geological environments in the early Precambrian (Huston and Logan 2004; Bekker et al. 2010). BIFs serve as records of formation and evolution i
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