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首页> 外文期刊>Geoscience journal >Geochemical studies of banded iron formations (BIFs) in the North China Craton: a review
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Geochemical studies of banded iron formations (BIFs) in the North China Craton: a review

机译：华北地球化学（BIFS）的地球化学研究克拉登：综述

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摘要

Majority of the banded iron formations (BIFs) in China are hosted in North China Craton (NCC). The BIFs in NCC are interlayered with metamorphics including amphibolite, and mainly composed of quartz, magnetite, and hematite with minor minerals such as garnet, epidote, chlorite, calcite, biotite, and pyrite. They were formed during from Paleoarchean to the early Paleoproterozoic with a peak at Neoarchean. Wall rock and Fe ore bodies in the BIFs have experienced greenschist to granulite facies metamorphism. Because of the intensive post-ore geologic activities, ores in the BIFs in NCC are characterized as low Fe grade (30.35 wt% of Fe in average) compared to those in the world. Most of the BIFs in China are affiliated into Algoma-type BIF. The Fe ores are composed of SiO2 and Fe2O3 (T) with minor Al2O3, MgO, CaO, Rb, Sr, Zr, Hf, Cr, and Co. Post Archean Average Shale (PAAS) normalized REY (rare earth elements with Y) patterns in the Fe ores show depletion in light REE (rare earth elements; LREE) compared to heavy REE (HREE) with positive La and Eu anomalies, suggesting that the Fe ores in BIFs were precipitated from the seawater with hydrothermal fluids. Trace elements ratios further suggest that the Fe and Si in the BIFs were derived from volcanic-related submarine hydrothermal fluids. Incorporation of continental-derived clastic materials are insignificant in most of the BIFs, while a few exhibit some incorporations. Ce anomalies in the Fe ore indicate an evolution of redox state during the BIF formation. Tectonic models in NCC and the formation of the BIFs were suggested by the geochemical and geological investigations in this study.
机译：中国的大多数带状铁形成（BIFS）在华北克拉顿（NCC）举办。 NCC中的BIFS与包括倒置的变质形状，主要由石英，磁铁矿和赤铁矿组成，少量矿物如石榴石，蛇类，氯酸盐，方解石，Biotite和黄铁矿。它们在从古地基期间形成的早期古普罗佐古代古普罗特在Neoarchean的峰值。 BIF中的壁岩和Fe矿体体验已经经历过Greenschist To Grarulite Face的变质形态。由于密集的矿石地质活动，NCC中的BIF中的矿石的特征在于与世界上的低FE等级（平均为30.35重量％）。中国的大部分BIF都是亚洲藻型BIF的。 Fe矿石由SiO2和Fe2O3（t）组成，用次要的Al2O3，MgO，CaO，RB，SR，Zr，HF，Cr和Co.邮政编码平均页岩（PAAS）标准化Rey（具有Y）模式的稀有地球元素在Fe矿石中，与阳性La和欧盟异常的重型REE（HREE）相比，在轻质REE（稀土元素; LREE）中显示出耗尽，表明BIF中的FE矿石从海水中沉淀着水热流体。痕量元素比例进一步表明BIF中的Fe和Si衍生自来自Volcanic相关的潜水液热液流体。在大多数BIF中，加入欧洲衍生的碎屑材料是微不足道的，而一些展示一些含量。 Fe矿石中的Ce异常表示BIF形成期间氧化还原状态的演变。本研究中的地球化学和地质调查提出了NCC中的构造模型和BIF的形成。

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