Prospectivity analysis of gold and iron oxide copper-gold-(silver) mineralizations from the Faina Greenstone Belt, Brazil, using multiple data sets

ABSTRACT: The Faina Greenstone Belt is located in the southern sector of the Goiás Archean Block and has been investigated since the 18th century because of its gold deposits. Recent studies have revealed the polymetallic potential of the belt, which is indicated by anomalous levels of Ag, Cu, Fe and Co in addition to Mn, Ba, Li, Ni, Cr and Zn. This study was developed based on a detailed analysis of two selected target sites, Cascavel and Tinteiro, and multiple data sets, such as airborne geophysics, geochemistry and geological information. These datasets were used to create a final prospectivity map using the fuzzy logic technique. The gold mineralization of Cascavel target is inserted in an orogenic system and occurs in two overlapping quartz veins systems, called Mestre-Cascavel and Cuca, embedded in quartzite with an average thickness 50 cm and guidance N45º-60ºW/25ºSW with free coarse gold in grains 2-3 mm to 3 cm. The prospectivity map created for this prospect generated four first-order favorable areas for mineralization and new medium-favorability foci. The Tinteiro area, derived from studies conducted by Orinoco do Brasil Mineração Ltda., shows polymetallic mineralization associated with an iron oxide-copper-gold ore deposit (IOCG) system posterior to Cascavel target mineralization. Its prospectivity map generated 19 new target sites with the potential for Au, Cu and Ag mineralization, suggesting new directions for future prospecting programs.

摘要：法因阿绿岩带（Faina Greenstone Belt）位于戈亚斯太古宙地块（Goiás Archean Block）南部区域，自18世纪起便因其金矿床而受到勘探研究。近期研究揭示了该绿岩带的多金属成矿潜力，除锰（Mn）、钡（Ba）、锂（Li）、镍（Ni）、铬（Cr）、锌（Zn）外，银（Ag）、铜（Cu）、铁（Fe）与钴（Co）的异常含量均印证了该潜力。本研究基于对卡斯卡韦尔（Cascavel）与廷泰罗（Tinteiro）两处选定靶区的详细分析，结合航空地球物理、地球化学与地质资料等多类数据集开展，通过模糊逻辑技术构建了最终成矿预测图。卡斯卡韦尔靶区的金成矿作用产出于造山系统中，赋存于两套叠置的石英脉系统内，分别为梅斯特雷-卡斯卡韦尔（Mestre-Cascavel）与库卡（Cuca）脉系，其赋存围岩为平均厚度50cm的石英岩，脉系走向为N45°-60°W/25°SW，产出的自然粗金颗粒粒径介于2~3mm至3cm之间。本次为该靶区生成的成矿预测图圈定了4处一级成矿有利区，以及若干新的中等有利成矿靶点。廷泰罗区域的资料源自巴西奥里诺科矿业有限公司（Orinoco do Brasil Mineração Ltda.）的相关研究，其发育的多金属成矿作用与氧化铁-铜-金（IOCG）矿床系统相关，成矿时代晚于卡斯卡韦尔靶区。该靶区的成矿预测图圈定了19处具备金、铜、银成矿潜力的新靶区，为未来勘探工作指明了新方向。