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Climate and Pyrite: Two factors to control the evolution of abandoned tailings in Northern Chile
Journal of Geochemical Exploration ( IF 3.4 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.gexplo.2020.106686
Javiera Gerding , Alexey A. Novoselov , Juan Morales

Abstract The environmental impact of abandoned sulfide-bearing tailings mainly associated with the generation of highly acidic, toxic waters causes a widespread public concern. Meanwhile, a fundamental understanding of the relationship between the secondary mineralogy produced by pyrite dissolution and the wind erosion on these artificial deposits has remained elusive. Here we address this gap in knowledge by elucidating the factors that control the tailings surface erodible by wind. Chile has developed its mining industry for decades, mainly in the north of the country, where desert landscapes dominate. Many of the tailings have been abandoned to the weather. Two areas of study with different climates ranging from arid to semiarid were evaluated by mineralogy, chemistry and particle size. Using statistical analysis, we demonstrated that it is possible to establish distinct types of alterations, which differ in secondary mineralogy mainly, giving rise three clusters: feldspar-dominated (without secondary mineralization), goethite-dominated and jarosite-dominated (with presence of efflorescent salts). When observing these clusters in the field, different surfaces characterize by contrasting cohesion and wind erodibility potential. Although selected clusters in both deposits share a similar set of minerals, the particle size, amount of pyrite and its by-products vary from one site to another. In addition, the microscopic morphology of the pyrite grains from both the uppermost section and deeper levels of the tailings reveals greater oxidation/dissolution in semiarid climate over arid climate, as well as more spherical particles in the surface levels and elongated ones in depth. Together, these data evidence that pyrite alone, regardless of its content and particle size, does not generate acidic solutions leading to the precipitation of secondary phases. The extent of secondary mineralization is also linked to the climate (available humidity), tailing permeability and pH-neutralizing primary phases. Depending on these variables, different potentially erodible surfaces showing to a greater or lesser cohesion of particles and higher or lower contents of toxic metals, which, in turn, is the reason for these tailings to become a public health issue.

中文翻译:

气候和黄铁矿:控制智利北部废弃尾矿演变的两个因素

摘要 废弃含硫化物尾矿的环境影响主要与高酸性、有毒水体的产生有关,引起了公众的广泛关注。同时,对黄铁矿溶解产生的次生矿物与这些人工沉积物的风蚀之间的关系的基本理解仍然难以捉摸。在这里,我们通过阐明控制可被风蚀的尾矿表面的因素来解决这一知识差距。智利几十年来一直在发展其采矿业,主要是在该国北部,那里以沙漠景观为主。许多尾矿已被遗弃在天气中。从干旱到半干旱的不同气候的两个研究领域通过矿物学、化学和颗粒大小进行了评估。使用统计分析,我们证明有可能建立不同类型的蚀变,这些蚀变主要在次生矿物学上有所不同,产生三个簇:长石为主(没有次生矿化)、针铁矿为主和黄钾长石为主(存在风化盐)。在实地观察这些集群时,不同表面的特点是内聚力和风蚀潜力形成对比。尽管两个矿床中选定的集群共享一组相似的矿物,但不同地点的黄铁矿及其副产品的粒度、数量不同。此外,尾矿最上段和更深层次的黄铁矿颗粒的微观形态表明,半干旱气候下的氧化/溶解大于干旱气候,以及在表面水平更多的球形颗粒和在深度上拉长的颗粒。总之,这些数据证明单独的黄铁矿,无论其含量和粒度如何,都不会产生导致第二相沉淀的酸性溶液。次生矿化的程度还与气候(可用湿度)、尾矿渗透率和 pH 中和初级阶段有关。根据这些变量,不同的潜在可侵蚀表面显示出或多或少的颗粒凝聚力和更高或更低的有毒金属含量,这反过来又是这些尾矿成为公共健康问题的原因。次生矿化的程度还与气候(可用湿度)、尾矿渗透率和 pH 中和初级阶段有关。根据这些变量,不同的潜在可侵蚀表面显示出或多或少的颗粒凝聚力和更高或更低的有毒金属含量,这反过来又是这些尾矿成为公共健康问题的原因。次生矿化的程度还与气候(可用湿度)、尾矿渗透率和 pH 中和初级阶段有关。根据这些变量,不同的潜在可侵蚀表面显示出或多或少的颗粒凝聚力和更高或更低的有毒金属含量,这反过来又是这些尾矿成为公共健康问题的原因。
更新日期:2021-02-01
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