Copper-bearing silicate minerals are relatively resistant to hydrometallurgical leaching. More efficient extraction of this residual Cu requires detailed knowledge of the mineralogical and textural settings of the minerals, which we outline in this study. Supergene oxidation and alteration of Fe-rich rocks at the Salobo iron-oxide copper–gold (IOCG) mine, Brazil, has caused transformation of primary phyllosilicates, especially biotite, to Cu-bearing clay minerals. The Cu replaced Fe and Mg most likely in the octahedral sites of vermiculite (up to 10 wt% Cu) and the Cu became part of the silicate structure, rather than being merely adsorbed to surfaces. This alteration from biotite has involved negligible textural changes, so that much of the Cu-vermiculite is encapsulated in less-altered biotite at µm to mm scales. More advanced alteration yielded Cu-bearing kaolinite (typically ~ 1 wt% Cu). Mobilisation of Cu under circumneutral pH conditions also led to local formation of veins of Cu-bearing minerals including chrysocolla. The most intense supergene alteration produced mm- to sub-μm-scale veins and cement made up of Cu-bearing quartz, kaolinite and goethite. Titanium derived from alteration of Fe-silicates pervades the altered rocks, coating Cu-silicate material at the μm-scale and this coating may further hinder leachability. Experimental acid (pH 2.2) (bio)leaching columns demonstrated that the presence of the bacterium Acidithiobacillus ferrooxidans did not significantly enhance Cu leach efficiency. However, the experiments, combined with thermodynamic modelling suggest that residual Cu from Cu-silicates can be extracted with acid solutions, although long-term leaching (months-years) may be required. Interactions between acid solutions and clay-altered silicates caused partial neutralisation (to ~ pH 5), further hindering leaching of residual Cu. Our study on the differences between alteration and precipitation textures provides useful context for designing suitable extraction processes for residual Cu from Cu-bearing silicate minerals in weathered rocks.

含铜硅酸盐矿物相对抗湿法冶金浸出。要更有效地提取这种残留的铜，需要对矿物的矿物学和组织结构有详细的了解，我们在本研究中对此进行了概述。巴西Salobo氧化铁铜金矿（IOCG）的超基因氧化和富铁岩石的蚀变已导致原生页硅酸盐（尤其是黑云母）转变为含铜粘土矿物。Cu最有可能在ver石的八面体位点（高达10 wt％Cu）替代Fe和Mg，并且Cu成为硅酸盐结构的一部分，而不仅仅是吸附到表面。黑云母的这种变化所涉及的结构变化可忽略不计，因此许多铜is石都被封装在变化较小的黑云母中，微米级至毫米级。更高级的蚀变产生了含铜高岭石（通常〜1 wt％Cu）。Cu在环境pH值条件下的动员也导致局部形成含铜矿物（包括金雀胶）的矿脉。最强烈的超基因改变产生了毫米级至亚微米级的静脉和由含铜石英，高岭石和针铁矿组成的水泥。源自铁硅酸盐蚀变的钛弥漫在蚀变的岩石中，以微米级覆盖铜硅酸盐材料，并且该涂层可能进一步阻碍浸出。实验酸（pH 2.2）（生物）浸提柱证明了细菌的存在 最强烈的超基因改变产生了毫米级至亚微米级的静脉和由含铜石英，高岭石和针铁矿组成的水泥。源自铁硅酸盐蚀变的钛弥漫在蚀变的岩石中，以微米级覆盖铜硅酸盐材料，并且该涂层可能进一步阻碍浸出。实验酸（pH 2.2）（生物）浸提柱证明了细菌的存在 最强烈的超基因改变产生了毫米级至亚微米级的静脉和由含铜石英，高岭石和针铁矿组成的水泥。源自铁硅酸盐蚀变的钛弥漫在蚀变的岩石中，以微米级覆盖铜硅酸盐材料，并且该涂层可能进一步阻碍浸出。实验酸（pH 2.2）（生物）浸提柱证明了细菌的存在酸性氧化硫杆菌铁氧体并没有显着提高铜浸出效率。然而，结合热力学模型的实验表明，尽管可能需要长期浸出（月-年），但可以用酸性溶液提取铜硅酸盐中的残留铜。酸溶液和改变粘土的硅酸盐之间的相互作用导致部分中和（至〜pH 5），进一步阻碍了残留铜的浸出。我们对蚀变和降水质地差异的研究为设计从风化岩石中含铜硅酸盐矿物中残留铜的合适提取工艺设计提供了有用的背景。