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首页> 外文OA文献 >Genesis of BIF-hosted hematite iron ore deposits in the central part of the Maremane anticline, Northern Cape Province, South Africa
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Genesis of BIF-hosted hematite iron ore deposits in the central part of the Maremane anticline, Northern Cape Province, South Africa

机译：BIF主持的赤铁矿铁矿床的成因，位于南非北开普省maremane背斜的中部

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The Paleoproterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to high-grade BIF-hosted hematite iron-ore deposits and is the country’s most important source of iron to date. Previous work has failed to provide a robust and all-inclusive genetic model for such deposits in the Transvaal Supergroup; in particular, the role of hydrothermal processes in ore-genesis has not been adequately clarified. Recent studies by the author have produced evidence for hydrothermal alteration in shales (Olifantshoek Supergroup) stratigraphically overlying the iron-ore intervals; this has highlighted the need to reassess current ore-forming models which place residual supergene processes at the core of oregenesis. This thesis focuses on providing new insights into the processes responsible for the genesis of hematite iron ores in the Maremane anticline through the use of newly available exploration drill-core material from the centre of the anticline. The study involved standard mineralogical investigations using transmitted/reflected light microscopy as well as instrumental techniques (XRD, EPMA); and the employment of traditional whole-rock geochemical analysis on samples collected from two boreholes drilled in the centre of the Maremane anticline, Northern Cape Province. Rare earth element analysis (via ICP-MS) and oxygen isotope data from hematite separates complement the whole-rock data. Iron-ore mineralisation examined in this thesis is typified by the dominance of Fe-oxide (as hematite), which reaches whole-rock abundances of up to 98 wt. % Fe₂O₃. Textural and whole-rock geochemical variations in the ores likely reflect a variable protolith, from BIF to Fe-bearing shale. A standard supergene model invoking immobility and residual enrichment of iron is called into question on the basis of the relative degrees of enrichment recorded in the ores with respect to other, traditionally immobile elements during chemical weathering, such as Al₂O₃ and TiO₂. Furthermore, the apparently conservative behaviour of REE in the Fe ore (i.e. low-grade and high-grade iron ore) further emphasises the variable protolith theory. Hydrothermally-induced ferruginisation is suggested to post-date the deposition of the post-Transvaal Olifantshoek shales, and is likely to be linked to a sub-surface transgressive hydrothermal event which indiscriminately transforms both shale and BIF into Fe-ore. A revised, hydrothermal model for the formation of BIF-hosted high-grade hematite iron ore deposits in the central part of the Maremane anticline is proposed, and some ideas of the author for further follow-up research are presented.
机译：南非北开普省的古元古代德瓦瓦河超级群是由BIF托管的赤铁矿铁矿床的高档储藏地，也是该国迄今为止最重要的铁资源。先前的工作未能为德兰士瓦超级集团中的此类矿床提供一个强大且包罗万象的遗传模型。特别是，尚未充分阐明水热过程在成矿作用中的作用。作者最近的研究为页岩（奥利芬舒克超群）地层上铁矿石层段的热液蚀变提供了证据。这突出了需要重新评估当前的成矿模型，该模型将残余的超基因过程置于成矿的核心位置。本文的重点是通过使用来自背斜中心的最新勘探钻芯材料，提供对造成Maremane背斜中赤铁矿铁矿石成因的过程的新见解。该研究涉及使用透射/反射光显微镜以及仪器技术（XRD，EPMA）进行标准的矿物学研究。并采用传统的全岩石地球化学分析方法，对从北开普省马雷马尼背斜中心钻出的两个钻孔收集的样品进行分析。稀土元素分析（通过ICP-MS）和赤铁矿分离出的氧同位素数据补充了整个岩石数据。本文研究的铁矿石矿化特征是Fe-氧化物（作为赤铁矿）占主导地位，其全岩丰度达到98 wt％。 ％Fe 2 O 3。矿石中的质地和全岩地球化学变化可能反映了从BIF到含铁页岩的原生岩体变化。根据矿石中记录的相对于化学风化过程中其他传统上不可移动的元素（例如Al 2 O 3和TiO 2）相对于其他传统上不可移动的元素的相对富集程度，提出了一个标准的超基因模型，该模型需要铁的固定化和残留富集。此外，铁矿石（低品位和高品位铁矿石）中稀土元素的表观保守性进一步强调了可变原石理论。建议水热诱导的铁素化作用要晚于Transvaal Olifantshoek后页岩的沉积，并且可能与次表层海侵性热液事件有关，后者不加区别地将页岩和BIF转变为铁矿石。提出了一种在Maremane背斜中部形成BIF的高品位赤铁矿铁矿床形成的修正水热模型，并提出了一些作者的想法，以便进一步进行后续研究。

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