Spatial Component Analysis to Improve Mineral Estimation Using Sentinel-2 Band Ratio: Application to a Greek Bauxite Residue

Roberto Bruno,Francesco Tinti,Efthymios Balomenos,Sara Kasmaeeyazdi,Emanuele Mandanici

doi:10.3390/min11060549

Abstract

Remote sensing can be fruitfully used in the characterization of metals within stockpiles and tailings, produced from mining activities. Satellite information, in the form of band ratio, can act as an auxiliary variable, with a certain correlation with the ground primary data. In the presence of this auxiliary variable, modeled with nested structures, the spatial components without correlation can be filtered out, so that the useful correlation with ground data grows. This paper investigates the possibility to substitute in a co-kriging system, the whole band ratio information, with only the correlated components. The method has been applied over a bauxite residues case study and presents three estimation alternatives: ordinary kriging, co-kriging, component co-kriging. Results have shown how using the most correlated component reduces the estimation variance and improves the estimation results. In general terms, when a good correlation with ground samples exists, co-kriging of the satellite band-ratio Component improves the reconstruction of mineral grade distribution, thus affecting the selectivity. On the other hand, the use of the components approach exalts the distance variability.

Highlights

According to “Mining and Metal in a Sustainable World 2050” [1], a major gap exists in effective retreatment technology of mining residues to meet the sustainability objectives of United Nations Development Program (UNDP)
This paper proposes to map the iron concentration as the strategic metal within a bauxite residue in Greece
If remote sensing data are used as a secondary variable, the space-time concept should be considered because ground samples are taken in a certain time, while satellite information is repeated over time; this produces photographs of “different” stockpiles

Summary

Introduction

Recovery of Minerals from Stockpiles and Tailings. Mining has been present everywhere in Europe, nowadays the majority of sites are closed. This does not mean that resources have been completely depleted. Ancient mining could not benefit from the most modern extraction and processing techniques and has left significant amounts of mining residue (including tailings and stockpiles) currently present in the territory, in the forms of semi-artificial hills, lakes, and ponds. According to “Mining and Metal in a Sustainable World 2050” [1], a major gap exists in effective retreatment technology (reuse, resize, or remove) of mining residues to meet the sustainability objectives of United Nations Development Program (UNDP)

Methods

Results

Discussion

Conclusion