Abstract
Abandoned mining wastes are both an environmental challenge and a possible secondary raw material source. The characterization and monitoring of these sites are often expensive and cumbersome because of the need of repeated field surveys. Remote sensing data are a cost-effective alternative that helps in producing multiscale maps of mining wastes. These maps can be used to investigate and monitor the spatial patterns of different elements within the mining wastes. In this work, Sentinel-2 images are combined with the geochemical samples in order to map the distribution of iron, copper, chromium, and cobalt. The target area was the Vigonzano mining wastes in Northern Apennines (Italy) where there are a small number of geochemical analyses but a large amount of satellite image data. We used the multivariate geostatistical estimation method (Co-Kriging) that exploit the meaningful spatial correlation between the elements of interest and band ratios (obtained from Sentinel-2 images). The concentration maps highlighted subareas for Cu and Cr with an estimated grade of about 0.3% and 0.2%, respectively. In addition, the critical element Co showed an enrichment in the south-east part of the mining wastes, in a similar pattern as Cr. Instead, the obtained maps show Ce, La, Rb, and Nb depletion compared to the surrounding agricultural areas. The concentration maps were intended as a prefeasibility study to determine enriched areas for further detailed investigation.
Highlights
In the energy transition time, there is an effort towards a society less dependent on oil and gas
The loss on ignition (LOI) was large in both sample groups within the mining waste (4.45–16.52 wt %), in comparison with the surrounding areas (9.81–16.98 wt %)
The concentrations of Cr, Co, Cu, and V were enriched in the mining waste area compared to the surrounding areas (Figure 4)
Summary
In the energy transition time, there is an effort towards a society less dependent on oil and gas. The energy transition requires critical metals to sustain a low-CO2 economic and social development. The CRM supply can derive from primary and secondary sources such as extraction mining wastes (stockpiles and tailings) stored at mine sites. The old mining wastes could represent a significant raw material source considering the deficiency of the old extraction and processing methods. The uppermost, ophiolite-bearing tectonic unit is known as the Ligurian Domain and it is traditionally divided into Internal and External Ligurian Domains (Figure 1). The former represents the oceanic lithosphere close to the rifting zone, and the latter is interpreted as a transitional zone towards the Adria continental margin.
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