Abdellatif Elghali1*, Mostafa Benzaazoua1, Hassan Bouzahzah2, Heather E. Jamieson3, Manuel Munoz4, James J. Dynes5
1 Geology and Sustainable Mining Institute, Mohammed VI Polytechnic University, Hay Moulay Rachid Lot 660, Benguerir, Morocco
2 Université de Liège, Génie minéral, matériaux et environnement, Allée de la découverte,
13/A. Bât. B52/3 Sart-Tilman, 4000 Liège, Belgium
3 Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, ON K7L 3N6, Canada
4 Geosciences Montpellier, Université de Montpellier, CNRS, Montpellier, France
5 Canadian Light Source, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada
Abstract: Investigations of the Joutel closed mine revealed the formation of cementitious layers or hardpans. These layers, formed at the interface between the oxidized and fresh tailings, are formed due to the massive precipitation of secondary minerals like Fe-oxyhydroxides and gypsum, which reduces the porosity and the permeability of the mine tailings. Chemically the studied hardpans are mainly composed of 25 wt.% Fe, 5.5 wt.% S, 3.2 wt.% Ca. In terms of trace elements, As content was around 749 ppm. Automated mineralogy analysis showed that the hardpans are composed of 68 wt.% of Fe-oxyhydroxides, 13 wt.% quartz 7.5 wt.% pyrite, and other minerals. Electron microprobe analysis showed that As is contained in the secondary Fe-oxyhydroxides. The As immobilized by Fe-oxyhydroxides can be released if they are dissolved. The durability of hardpans investigated using monolithic leaching tests showed that they can be considered as low-reactivity layers with slow-release rates of chemical species.