The main goal of this study was to identify potential chemical elements present in three types of polymetallic mine waste, stored in the old mine site of São Domingos, located in the Iberian Pyrite Belt, Alentejo, Southern Region of Portugal. This study involves the characterization of potential resources in those mine residues, bearing in mind that its reprocessing can facilitate the environmental remediation and rehabilitation activities which are underway at the site. X-ray Fluorescence (XRF) and micro (μ)-XRF 2D mapping surveys were performed. Univariate and multivariate data analysis reveal that differences in compositions are mainly related with element concentration per type of waste. Image processing and clustering analysis allowed the recognition of distinct elemental spatial distribution patterns. Some of these residues, although classified as archeological-industrial heritage materials may present toxicity to the ecological environment and to human health. This fact enhances, therefore, geoethical doubts regarding its remining and exploitability. In this context, a multi-criteria decision analysis considering two geoethical alternatives was performed.

<p>Post-Mining Land Use (PMLU) corresponds to the new use given to the land impacted by mining activities. The decision for the new land use requires consideration and analysis regarding many technical aspects and will impact several stakeholder groups. At the same time, PMLU corresponds to what will follow after the mineral resource is exhausted (ideally), which leaves the site and communities without the biological and geological richness they had. However, although the original features do not exist, new features can satisfy all stakeholders’ needs. Therefore, PMLU decisions should be framed by geoethical thinking, embedding its principles and values in a Multi-Criteria Decision Analysis (MCDA).</p><p>Multi-Criteria Decision Analysis (MCDA) is a methodology used to analyse decisional problems where multiple, often, conflicting criteria are in place. Therefore, the most critical stage is structuring the problem under analysis. The result of this problem structuring is the definition of criteria and alternatives, considering the values of all interest groups to the decision (all stakeholders). This analysis is highly relevant in themes where local populations are affected by the decision, such as PMLU. The embodiment of geoethics thinking in this process is of essential role because the PMLU corresponds to a new land-use change that must happen due to human use of natural resources. The example of São Domingos abandoned mine (Portugal) will be used for this study.</p><p>São Domingos mine is an abandoned mine located in the Portuguese sector of the Iberian Pyrite Belt (IPB). IPB is a world-class Volcanic-Hosted Massive Sulphide metallogenic province formed in the Iberian Variscan orogeny (Paleozoic age). São Domingos’ ore was exploited throughout times, in the Pre-Roman Period (several centuries in the first millennium B.C.), Roman Period (approximately from 14 B.C. until 395 B.C.), Islamic Period, and Modern Period (between 1854 and 1966). The primary metals and minerals extracted in historical periods were silver, copper and probably gold. In the Modern Period, the main ores extracted were cupriferous pyrite, roasted pyrite, sulfur, and copper.</p><p>All exploitation periods left important features. For example, archaeological records of ancient slags with high value for local and national history and culture are preserved from the pre-roman and Roman periods. However, from the modern period, heaps of ore processing wastes also exist, which generate AMD propagating for several kilometres downstream. At the same time, all these features bear critical raw materials. Therefore, regarding the environmental recovery model, a geoethical dilemma poses: should we extract the critical raw materials from all wastes and contribute to a circular economy model, or preserve these historical records in controlled environmental conditions?</p><p>With this example, the authors wish to explore how to embed geoethical thinking and values into the MCDA for post-mining land use, using the need to control and remediate the environmental issues of an abandoned mine.</p>

In mine design and planning, identifying appropriate Post-Mining Land Use (PMLU) is necessary and crucial to achieving environmental quality and socioeconomic renewal. In this context, Multi-Criteria Decision Making (MCDM) methods are used to support decision-maker and stakeholder decisions. However, most studies regarding the application of MCDM methods to PMLU decisions do not favor their widespread use because they start from an already structured decisional problem. The structure they present may not apply to another PMLU decision. Therefore, the primary goal of this study is to present an innovative methodology and its corresponding framework to help decision-makers and stakeholders structure their PMLU decisions. This innovative methodology can be used from an early stage, with a low level of detail, until a later stage, with a high level of detail, and is composed of three main stages. The first stage is selecting the Transitional Post-Mining Landscape Profile, which guides the user to different Multi-Criteria Decision Analysis (MCDA) goals. The second stage is developing criteria and alternatives according to the MCDA goal, using topics representing essential dimensions that cannot be disregarded, and testing the MCDM methods. Finally, the third stage is the participatory process and final application of MCDM methods.

In mine design and planning, the identification of an appropriate Post-Mining Land Use (PMLU) is necessary and crucial to achieve environmental quality, socio-economic renewal, and social acceptance of mining projects. In this context, Multi-Criteria Decision Making (MCDM) methods support decision-makers and stakeholders, identifying the relevant factors and criteria, so that, different available alternatives can be evaluated, compared, and contrasted with each other. With the vision to enable its wide application, 15 mine profiles are identified which, combined with selected MCDM methods and relevant factors, results in a Multi-Criteria Decision Analysis (MCDA) framework for PMLU. In this preliminary framework, the MCDM methods selected are SIMUS, TOPSIS, and SMARTER. They serve different problems and, therefore, are used in different profiles: SIMUS is applied to complex profiles, TOPSIS to the lesser ones, and SMARTER is used due to its capacity of assigning weights to criteria based on Ranking Order Centroid calculations. This preliminary MCDA structure gives the possibility to include the complexity (technical and decisional) and a participatory process, for all stakeholders involved concerning PMLU.