Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover, Germany.
Sci Total Environ. 2012 Jan 1;414:480-93. doi: 10.1016/j.scitotenv.2011.10.038. Epub 2011 Nov 25.
In this paper, mineral liberation analysis (MLA) was applied as a new approach to elucidate and quantify textural, mineralogical, and chemical variations on a μm/mm scale to understand the alteration processes relevant for hardpan formation at the Davidschacht mine tailings in Freiberg, Germany. Additionally, the bulk mineralogical, geochemical, and physical properties were investigated in detail. Within the upper 1.5m of this impoundment, a repetition was observed of oxidized sediments with pH values between 2 and 3, and of unoxidized sulfide/carbonate bearing sediments with pH values around 7.0. The alteration process was not homogeneous, as even within the same lamina different stages of oxidation were observed. According to the MLA measurements, the 2D pore area decreased from about 43 area-% in the unoxidized layers to 10.5-24.0 area-% in the hardpan layers, which is due to the accumulation of secondary precipitates. This clogging of pores was localized at the contact zone between two graded layers. The upper part of the lower layer consisted of very fine grained mica and chlorite fragments, which have a relatively high water retention capacity. This lamina was overlain by the bottom part of the next graded layer, which was characterized as relatively coarse grained with coarse open pores and an elevated content of primary reactive sulfides. This lamina provides access to oxygen and rain water to stimulate reactions, eventually supported by microbiological activity. Since graded layers might be amputated at top or bottom, the above described assemblage was not ubiquitous, but nevertheless multiple repetitions were encountered even at thin section level. The occurrence of these repetitions of slightly inclined tile like hardpans may reduce rain water and oxygen input at the rim of the impoundment. The application of MLA has opened up new opportunities for a better understanding of the sedimentological and mineralogical setup in relation to oxidation, transport, and precipitation processes on a μm scale within tailings impoundments.
本文应用矿物解离分析（MLA）作为一种新方法，在μm/mm 尺度上阐明和量化结构、矿物学和化学变化，以了解德国弗莱贝格达维施查赫特矿尾矿硬磐形成过程中的蚀变过程。此外，还详细研究了块状矿物学、地球化学和物理性质。在该坝体的上部 1.5m 范围内，观察到氧化沉积物的重复出现，其 pH 值在 2 到 3 之间，以及未氧化的含硫化物/碳酸盐沉积物，其 pH 值约为 7.0。蚀变过程不均匀，即使在同一纹层内，也观察到不同阶段的氧化。根据 MLA 测量结果，2D 孔隙面积从未氧化层的约 43 面积%减少到硬磐层的 10.5-24.0 面积%，这是由于次生沉淀的积累。这种孔隙堵塞是在两个分级层的接触带局部发生的。下层的上部由非常细粒的云母和绿泥石碎片组成，它们具有相对较高的持水能力。该纹层被下一个分级层的底部覆盖，其特征为相对粗粒，具有粗开口孔隙和升高的原生反应性硫化物含量。该纹层提供了氧气和雨水进入的通道，以刺激反应，最终得到微生物活动的支持。由于分级层可能在顶部或底部被截断，因此上述组合并非普遍存在，但即使在薄片水平上也多次遇到。这些略微倾斜的瓦片状硬磐的重复出现可能会减少坝体边缘的雨水和氧气输入。MLA 的应用为更好地理解尾矿坝内与氧化、传输和沉淀过程相关的沉积学和矿物学结构提供了新的机会，其尺度在μm 范围内。
