Mineralurgical and Environmental Characterization of the Mine Tailings of the IOCG Mine of Guelb Moghrein, Akjoujt, Mauritania  
[PERSON], [PERSON], [PERSON], [PERSON]  
inside the mining site in Tailings Storage Facilities (TSFs). This site is composed of three tailings ponds: TSF1 (5,055,259 Mt), TSF2 (23,694,803 Mt) and TSF3 (10,409,000 Mt). These tailings are hazardous with respect to the surrounding ecosystems and have negative socioeconomic repercussions on the communities. Like many other geochemical and geotechnical stability issues, the study of the environmental behavior of these mine tailings requires a good understanding of the various factors involved at the scale of the TSF ponds. Several transformations of the TSF mine tailings in their current state have been observed as a response to climate and site conditions that greatly affect the TSF, notably the geochemical processes which involve factors such as reduction-oxidation, dissolution, precipitation and adsorption-sorption [8; 9; 10; 11]. Reactive sulfide and arsenide minerals, such as pyrite (FeS\({}_{2}\)), pyrrhotite ((Fe\({}_{1-\text{x}}\)S), arsenopyrite (FeAsS), chalcopyrite (CuFeS\({}_{2}\)), cubanite (CuFe\({}_{2}\)S\({}_{3}\)), climosafflorite (Co,Fe,Ni)As\({}_{2}\)) and gersdorffite (NiAsS) in contact with water and air oxidize, leading to acid mine drainage (AMD) formation, and hence an increase in the solubility of various potentially toxic elements (PTEs) [11; 12; 13; 14; 15; 16; 17]. This phenomenon leads to the transfer of metallic trace elements (MTEs) to the soils and water resources (both surface and underground) which is harmful to biodiversity and health [18; 19]). However, the dissolution of carbonates and silicate minerals present in the mine tailings can neutralize the acidity produced [9; 12; 20; 21] and limit the impact of this phenomenon at the stage of contaminated neutral drainage (CND) [8; 22; 23; 24]. The formation of secondary minerals such as oxyhydroxides, hydroxysulfates, arsenates, sulfates and halides resulting from the neutralization of AMD can generate hardpan, which consists of dense and hard crusts in semi-arid climatic conditions [25]. The hardpan prevents water penetration and oxygen diffusion due to pore clogging; and consequently, it decreases porosity and permeability. Secondary minerals can also be considered as metal scavengers because of the significant retention capacity of metals by adsorbent minerals, which reduces the mobility of metals in the pore water and leads to their release into the surrounding environment [20; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39]. Moreover, the arid and hot climatic context of the Akjoujit region is characterized by high evaporation rates (>3500 mm/year) in addition to the increasing rainfall deficit (<70 mm/year) and a poor vegetation cover. Therefore, these climatic conditions underscore the precipitation of salt crusts on the surface, which once subjected to wind erosion can contaminate the surrounding ecosystems (water, air, soil) [40]. In addition to the complexity of these phenomena, we must refer to other geotechnical features such as the formation of cracks, matric suction, salt precipitation, crack clogging, crust consolidation and volumetric shrinkage, which may affect the stability of the TSF mine tailings. The overall objective of this study is to conduct, for the first time in Mauritania, a detailed mineralurgical and environmental characterization on the three TSF mine tailings in order to show the problems that the IOGC mining activities could generate on the environment under the arid climate conditions of Akjoujit. This must be completed before the end of mining operations in order to prevent high rehabilitation costs.