Laboratoire de Ressources Minérale et Environnement, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092, Tunis, Tunisia,
Environ Sci Pollut Res Int. 2015 Feb;22(4):2877-90. doi: 10.1007/s11356-014-3569-1. Epub 2014 Sep 16.
The underground extraction of Pb-Zn mineralization in the Touiref area stopped in 1958. A large volume of flotation tailings (more than 500 Mt) containing sulfides were deposited in a tailings impoundment. The goals of this study are to evaluate the neutralization capacity of the unoxidized and oxidized tailings, to assess the speciation of metals between the different components of the tailings material, and to assess the mobility of metals and the secondary minerals' precipitation in pore waters using geochemical modeling. To accomplish these objectives, representative samples from both fresh and oxidized zones were collected along a vertical profile through the tailings pile. Physical, chemical (ICP-MS), and mineralogical characterization (X-ray diffraction (XRD), reflected light microscopy, scanning electron microscope (SEM)) of these samples was performed. Grain size analysis shows that the tailings are dominated by silt- to sand-sized fractions. The microscopic observation highlights the presence of pyrite, marcasite, galena, and sphalerite as primary minerals in a carbonated matrix. The study reveals also the presence of secondary minerals represented by cerussite, smithsonite, anglesite, and Fe oxi-hydroxides as important scavengers for trace elements. The static tests show that the presence of calcite in the tailing samples ensures acid-neutralizing capacity (ANC), which is significantly greater than the acidity potential (PA). The geochemical characterization of the unoxidized samples shows higher Cd, Pb, and Zn concentrations than the oxidized samples containing the highest values for Fe and SO4. Sequential extraction tests show that significant percentages of metals are distributed between the acid-soluble fractions (Cd, Pb, and Zn) and the reducible one (Zn). Pore water analysis indicates that Ca is the dominant cation (8,170 and 6,200 mg L(-1), respectively), whereas sulfate is the principal anion (6,900 and 5,100 mg L(-1), respectively). Saturation index (SI) calculations of minerals in pore water extracted from both the oxidized and unoxidized samples are indicative of gypsum (SI >0) and Fe(III) oxides (SI ≫0) precipitation. The latter controls the Fe concentration in solution.
图雷雷夫地区的地下铅锌矿化开采于 1958 年停止。大量含有硫化物的浮选尾矿（超过 500Mt）被储存在尾矿库中。本研究的目的是评估未氧化和氧化尾矿的中和能力，评估尾矿物质不同成分之间金属的形态，以及使用地球化学模拟评估金属的迁移性和次生矿物在孔隙水中的沉淀。为了实现这些目标，沿着尾矿堆的垂直剖面采集了新鲜区和氧化区的代表性样品。对这些样品进行了物理、化学（ICP-MS）和矿物学特征（X 射线衍射（XRD）、反射光显微镜、扫描电子显微镜（SEM））分析。粒度分析表明，尾矿主要由粉砂到砂级颗粒组成。微观观察突出了方铅矿、白铁矿、闪锌矿和菱锌矿作为碳酸盐基质中的原生矿物的存在。研究还表明，次生矿物以白铅矿、菱锌矿、硫酸铅和铁的氧化氢化物为代表，是痕量元素的重要清除剂。静态试验表明，尾矿样品中方解石的存在确保了酸中和能力（ANC），ANC 明显大于酸度潜力（PA）。未氧化样品的地球化学特征表明，Cd、Pb 和 Zn 的浓度高于含有最高 Fe 和 SO4 的氧化样品。连续提取试验表明，金属的很大一部分分布在酸可溶部分（Cd、Pb 和 Zn）和可还原部分（Zn）之间。孔隙水分析表明，Ca 是主要阳离子（分别为 8170 和 6200mg/L），而硫酸盐是主要阴离子（分别为 6900 和 5100mg/L）。从氧化和未氧化样品中提取的孔隙水中矿物的饱和度指数（SI）计算表明石膏（SI>0）和 Fe（III）氧化物（SI>0）沉淀。后者控制溶液中 Fe 的浓度。
