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Geochemical constraints on the genesis of the Ekou banded iron formation, Shanxi Province, North China
International Journal of Earth Sciences ( IF 1.8 ) Pub Date : 2020-10-01 , DOI: 10.1007/s00531-020-01935-4
Yekai Men , Ende Wang , Jianfei Fu , Sanshi Jia , Xinwei You , Qiangwen He

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 SiO2 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.



中文翻译:

华北山西鄂口带状铁矿成因的地球化学约束

五台地区的Ekou带状铁层(BIF)处于晚太古宙白芝岩组内。矿物组合用于识别氧化物和硅酸盐相。氧化物相由磁铁矿和石英组成,而硅酸盐相的特征是存在硅酸盐矿物。地球化学分析表明,主要元素组成主要为SiO 2和Fe 2 O 3 T,很少有Al 2 O 3和TiO 2。以及少量不兼容元素和过渡元素。这些结果表明,可忽略的陆源物质参与了BIF沉积。稀土元素(REE)通过Archean后澳大利亚页岩进行归一化,具有轻REE(LREE)耗尽,重REE(HREE)富集以及正,负,负和,异常的特征。Y / Ho比是超软骨的。这些结果表明,形成Ekou BIF的材料起源于海水和海底热液的混合。Ce异常缺乏和大量Fe同位素富集表明Ekou BIF在缺氧海洋环境中形成。的δ 30的Si NBS-28Ekou BIF中石英的值与其他BIF相似,具有现代烧结矿和黑烟的分布范围。的δ 18 ö V-SMOW分布是类似的热水沉积硅质岩。这些结果表明,Ekou BIF的形成与海底火山呼出活动密切相关。

更新日期:2020-10-26
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