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首页> 外文期刊>Brazilian Journal of Geology >The Cristalino IOCG deposit: an example of multi-stage events of hydrothermal alteration and copper mineralization
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The Cristalino IOCG deposit: an example of multi-stage events of hydrothermal alteration and copper mineralization

机译：Cristalino IOCG矿床：热液蚀变和铜矿化多阶段事件的一个例子

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The Cristalino deposit is located 40 km east of Sossego mine, Carajás. The orebody lies along a NW-SE-striking shear zone and is mainly hosted by the Neoarchean bi-modal volcanics of the Gr?o Pará Group. Field work and petrographic data seconded by SEM-EDS analysis allowed recognizing an early sodic metasomatism that was followed by calcic-ferric, potassic and propylitic alterations, and finally by carbonatization. The volcanic rocks were altered under deformation regimes that changed from ductile-brittle to brittle. The deposit resulted from two mineralizing stages. The early stage took place at a greater depth and produced an ore association composed chiefly of chalcopyrite, pyrite, and magnetite as disseminations, breccia and veins particularly in Ca-Fe altered rocks. The later stage occurred at a shallower depth and formed a practically magnetite-free ore association, consisting essentially of chalcopyrite ± pyrite ± hematite in breccias and veins generated mostly during the potassic alteration. These ore associations indicate that the hydrothermal system evolved with temperature decrease and increase in fO 2, Cu/Fe ratio and sulfur activity. Cristalino is conceived as a multi-stage IOCG deposit similar to others lying in the Carajás E-W corridor of IOCG systems.
机译：Cristalino矿床位于CarajásSossego矿以东40公里处。该矿体位于NW-SE冲切剪切带上，主要由格罗帕拉集团的新archarean双峰火山岩所包裹。通过SEM-EDS分析获得的野外工作和岩石学数据可以识别出早期的钠系交代作用，随后是钙铁，钾和丙炔化蚀变，最后是碳化。火山岩在从韧性脆性变为脆性的变形机制下发生了变化。该矿床来自两个矿化阶段。早期发生在更深的深度，形成了主要由黄铜矿，黄铁矿和磁铁矿组成的矿石协会，它们的传播，角砾岩和脉脉尤其是在钙铁蚀变的岩石中。后期发生在较浅的深度，并形成了几乎无磁铁矿的矿石组合，基本上由角砾岩中的黄铜矿±黄铁矿±赤铁矿组成，且大部分在钾化蚀变过程中产生。这些矿石关联表明热液系统随着温度的降低以及fO 2，Cu / Fe比和硫活度的增加而演化。 Cristalino被认为是多阶段的IOCG矿床，与IOCG系统的CarajásE-W走廊中的其他矿床相似。

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