A multidisciplinary approach considering geochemical reorganization and internal structure of tailings impoundments for metal exploration

Tailings deposits may host a significant amount of valuable elements and are of great interest as exploration targets for secondary mining. However, elements are distributed heterogeneously within an impoundment due to physical and chemical processes during and after deposition. Therefore, the complex internal structure has to be considered for representative sampling, estimation of ore grade and to prevent dilution of metals by bulk mining. This study shows that a multidisciplinary approach and a combination of methods are necessary to take account of that. The selected methods comprise surface sampling with few drillings, geochemical and granulometric analysis and Electrical Resistivity Tomography (ERT). They provide important information for a quick decision about the economic viability of further detailed exploration or even secondary mining. In order to understand the internal structure of tailings impoundments collection of 1D and 2D information from sampling and drilling should be accompanied by 3D resistivity mapping. In this work, indications for particle size distribution, metal distribution and water movement were extracted from the different data sets and a model for the internal structure and re-organization is proposed. General zones of metal enrichment and depletion can be projected from the model. Furthermore, water saturation and movement as an important factor for acid rock drainage and tailings dam stability can be deduced for an estimation of the environmental risk of the tailings impoundment. Therefore, the proposed combination of methods covers both the estimation of economic potential as well as the analysis of environmental impacts of tailings deposits.