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首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >The BIF-Hosted High-Grade Iron Ore Deposits in the Archean Koolyanobbing Greenstone Belt, Western Australia: Structural Control on Synorogenic- and Weathering-Related Magnetite-, Hematite-, and Goethite-rich Iron Ore
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The BIF-Hosted High-Grade Iron Ore Deposits in the Archean Koolyanobbing Greenstone Belt, Western Australia: Structural Control on Synorogenic- and Weathering-Related Magnetite-, Hematite-, and Goethite-rich Iron Ore

机译：BIF承载的西澳大利亚太古宙库亚诺宾绿岩带中的高品位铁矿石矿床：富含与成矿作用和风化作用有关的磁铁矿，赤铁矿和针铁矿的铁矿石的结构控制

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摘要

The Koolyanobbing banded iron formation (BIF)-hosted iron ore deposits (total premining resources ～150 million metric tons (Mt), indicated reserves ～32 Mt) are located in the Mesoarchean lower succession BIF of the Koolyanobbing greenstone belt, Younami terrane, Yilgarn craton in Western Australia. In the Koolyanobbing greenstone belt a deformation sequence that broadly correlates with the proposed deformation history of most greenstones belts within the Southern Cross domain includes: D_1 structures (mainly small-scale F_(1a) and F_(1b) folds, formed in a north-south to northwest-southeast compressional regime), a ductile to brittle deformation sequence, D_2 to D_4 (generated during east-west compression) and, a late-stage brittle segmentation of BIF and reactivation of faults, attributed to D_5. The formation of the seven known medium- (45-58 wt % Fe) to high-grade (58-68 wt % Fe) magnetite-, martite-, specularite-, and goethite-bearing orebodies can be subdivided into four Archean stages and one weatherin related upgrade from the Permian and/or Mesozoic to recent times. The Archean ore-forming stages comprise: (1) early Fe-Mg ± Ca metasomatism causing local ferroan carbonate and ferroan talc alteration of the metamorphosed quartz-magnetite BIF protolith; (2) sequential syn-D_(2a) (coaxial) to syn-D_4 (transpressional) tight folding-driven removal of carbonate, quartz and minor ferroan talc by solution and mechanical transfer, producing residual enrichment of medium- to high-grade magnetite ore; (3) magnetite mineralization in syn-D_(2b) and syn-D_4 breccias and fractures, forming medium-grade ore zones, or overprint magnetite in BIF and first-stage magnetite ore; and (4) mineralization of hydrothermal specularite and locally associated ferroan dolomite-quartz alteration, and local oxidation of magnetite in and near brittle D_4 faults, fractures, and reactivated F_1 and F_(2a) fold cores. Modern weathering-related leaching of carbonate (and minor quartz), pseudomorphic goethite replacement of existing iron o des and gangue, and coeval or subsequent to oxidation in the vadose zone formed goethitemartite ore with local relics of specularite or magnetite and/or kenomagnetite. The intensity and localization of this supergene modification is, in most deposits at Koolyanobbing, controlled by existing hypogene magnetite, specularite-rich medium- to high-grade ore zones and/or carbonate-altered BIF at depth. The existence of high-grade ore below the weathering horizons suggests the possibility of further concealed magnetite- and/or specularite-rich orebodies within the deposits and region.
机译：Koolyanobbing带状铁矿（BIF）带动的铁矿床（总开采资源〜1.5亿吨（Mt），指示储量〜32 Mt）位于Koolyanobbing绿岩带，Younami terrane，Yilgarn的中上古统低层次生BIF中。西澳大利亚的克拉通。在Koolyanobbing绿岩带中，与南十字域内大多数绿岩带的拟议变形历史大致相关的变形序列包括：D_1结构（主要是小规模的F_（1a）和F_（1b）褶皱，形成于北缘。南至西北向东南的压缩模式，韧性至脆性变形序列，D_2至D_4（在东西向压缩过程中产生），以及BIF的后期脆性分段和断层活化，归因于D_5。可以将七个已知的中度（45-58 wt％Fe）到高品位（58-68 wt％Fe）磁铁矿，马氏体，镜铁矿和针铁矿矿体的形成分为四个太古宙阶段和一种与天气有关的从二叠纪和/或中生代到近代的升级。太古代的成矿阶段包括：（1）早期的Fe-Mg±Ca交代作用，引起变质的石英磁铁矿BIF原生岩的局部碳酸亚铁和铁滑石改变; （2）通过溶液和机械转移顺序将syn-D_（2a）（同轴）转换为syn-D_4（压性）紧密折叠驱动去除碳酸盐，石英和少量亚铁滑石，产生中到高品位磁铁矿的残余富集矿石; （3）syn-D_（2b）和syn-D_4角砾岩和裂缝中的磁铁矿成矿作用，形成中品位矿带，或在BIF和第一阶段磁铁矿中叠印磁铁矿; （4）热液高铁矿的矿化作用和与之相关的亚铁白云岩-石英的蚀变，以及脆性D_4断层，断裂以及重新活化的F_1和F_（2a）折叠岩心及其附近的磁铁矿的局部氧化。与现代风化有关的碳酸盐（和次要石英）的浸出，现有铁矿和脉石的假晶变质针铁矿置换以及在渗流带中的同等氧化或氧化之后，形成了针铁矿铁矿矿石，并与当地的镜面石或磁铁矿和/或磁铁矿遗迹。在Koolyanobbing的大多数矿床中，这种超基因修饰的强度和局限性都由现有的次生磁铁矿，富于镜矿的中高品位矿床和/或深部碳酸盐改变的BIF所控制。风化层以下的高品位矿石的存在表明在矿床和区域内可能进一步隐藏了富含磁铁矿和/或富于镜子石的矿体。

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