Economic Potential of Mining and Metallurgical Dumps, Taking into Account the Sustainability on the Example of the Western Harz Mountains (ROBEHA)

Country / Region: Germany / Harz

Begin of project: August 1, 2012

End of project: July 31, 2015

Status of project: July 31, 2015

Selected mine waste dump, containing residues from the processing of Pb-(Zn)-gangue ore. Due to the input of waste material into the adjacent river, a remediation of this dump is necessary Source: BGR

The increasing demand of mineral raw materials in recent years calls for new strategies for a secure supply for Germany. Whereas the recycling of metals and construction aggregates from urban waste has already been investigated and partially implemented, there is not much known about the economic potential of wastes from thousands of years of ore mining in Germany as a source for non-ferrous metals, high-tech metals and construction aggregates.

In the Harz Mountains, one of the most important ore mining districts for base and precious metals in Germany, approximately 1000 mine waste dumps from more than 1000 years of metal ore mining occur.

In cooperation with some partners (see below), BGR scientists investigate mining residues in several Western Harz mining districts as part of the BMBF-funded (Federal Ministry of Education and Research) research project ROBEHA (Project-No. 033R105).

The work packages of the BGR include general investigations of mine waste dumps of different origin and of different ore deposit districts in the Western Harz Mountains. Additionally, the resources of two promising dump sites are estimated by exploration of the internal structures of dump bodies and a detailed characterisation of the waste material.

Ore-processing tests of the mining residues for the extraction of valuable metals, as well as potential valuable inert residuals are done by our project partners. Furthermore, scenarios for the “mining” of these dumps and their environmental impact are discussed. In cooperation with other research projects exploring mining residues in Germany, an assessment approach for the recycling of mining dumps as well as a cadastre is developed.

The general investigations of several mining dumps in the Western Harz Mountains showed strong variations in the metal contents of the mine wastes. Metal concentrations are predominantly determined by the mine waste type (e.g. mining wastes, ore processing wastes, metallurgical wastes) and the composition of the original ore. Another important aspect is the time when the dump was constructed. This is due to the ore-processing technique and the metals, which were mined during that time.

As a result of the preliminary investigations a mine waste dump, containing ore-processing residues from density-separated Pb-(Zn) gangue ores of the “Upper Harz” near Bad Grund was chosen for a resource estimation (Figure). The material, which is characterized by high Pb-, Sb- and Ag-contents, was deposited at the dump site during 1904 and 1931.

The exploration of the heterogeneously structured body is realized by a combination of differently scaled methods. It starts with a large-scaled geophysical exploration, providing a basis for an estimation of the waste material volume and for definition of drilling locations. In consequence, the amount of samples can be reduced and the generation of pathways for water flow by extensive sampling can be limited. Beside electrical resistivity tomography (ERT) further geophysical techniques like RADAR and Spectral Induced Polarisation (SIP) have been used.

The split cores have been analysed with a LIBS Core Scanner (Laser-Induced Breakdown Spectroscopy) to generate 2D-element distribution images for major and minor elements. These images were used to identify zones of metal enrichment and provide a basis for the estimation of average metal concentrations as a basis for the resource calculation. Small-scaled chemical and mineralogical analysis of subsamples reveal further information about the metal distribution within the different mineral phases as well as the state of alteration of theses phases.

Partner:

• Prof. Burmeier Ingenieurgesellschaft mbH (BIG)
• Technische Universität Clausthal - Institut für Aufbereitung, Deponietechnik und Geomechanik (TU Clausthal IFAD),
• Clausthaler Umwelttechnik-Institut GmbH (CUTEC),
• Dorfner Analysenzentrum und Anlagenplanungsgesellschaft mbH (Dorfner ANZAPLAN)