The sandy Quaternary and the deep Maastrichtian aquifers located in the northern coastal zone of Senegal, from the locality of Kayar in the south to Saint-Louis in the north, constitute the main sources of water suppl...The sandy Quaternary and the deep Maastrichtian aquifers located in the northern coastal zone of Senegal, from the locality of Kayar in the south to Saint-Louis in the north, constitute the main sources of water supply for urban and local needs as well as mining activities. The Quaternary aquifer that provides the water required for the irrigation of local farmlands, hosts a significant heavy mineral sands deposit currently being mined by the Grande Cote Operations (GCO). As a result of variable rainfall and increased water abstraction, this shallow aquifer has recorded a continuous water level decline since 1970, with potential negative effects on both the social and economic development of the region. The mining of heavy minerals (zircon, ilmenite, leucoxene and rutile) at GCO is realised through conventional dredging techniques that require large volumes of water (up to 60,000 m3/d). The water pumped by the dredge to enable the extraction of the heavy minerals, infiltrates into the shallow aquifer, runs-off into the dredge pond or evaporates. The objective of this study is to evaluate a water balance that enables the provision of a permanent water supply to the dredge pond, whilst minimising the risk of flooding of the cropping depressions adjacent to the mine site or drying out of the farming wells. The hydrodynamic model implemented for this purpose was calibrated and tested during the first year of operation. The Root Mean Squared Error (RMSE) obtained for the calibration is approximately 0.52 m. The predictions indicate a requirement for the system to recover part of the tailings infiltration through dewatering boreholes. The quantity of recycled water is estimated at 16,000 m3/d on average. The model simulations show an additional water requirement, extracted from the deep Maastrichtian aquifer, varying between 23,000 and 28,000 m3/d to achieve the optimum pond water level.展开更多
Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zir...Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zircon, medium grade zircon standard) from Senegal’s heavy mineral sands. During mining separation, monazite, which is a paramagnetic mineral, was found in a non-negligible concentration of 0.57 wt% on average in the medium grade zircon standard which also contains 37.96 wt% zircon and 44.46 wt% titanium oxides. Magnetic and gravity separation tests were carried out on the Medium grade zircon standard (MGZS) to produce a monazite concentrate at Eramet Ideas laboratory. Magnetic separation at 1.5 teslas intensity resulted in the recovery of 94.8% of the monazite from the MGZS. Gravity separation also recovered 76.6% of the monazite from the MGZS. The combination of these two treatment methods can thus produce three concentrates from MGZS (a monazite concentrate, a zircon concentrate, and a titanium oxide concentrate).展开更多
文摘The sandy Quaternary and the deep Maastrichtian aquifers located in the northern coastal zone of Senegal, from the locality of Kayar in the south to Saint-Louis in the north, constitute the main sources of water supply for urban and local needs as well as mining activities. The Quaternary aquifer that provides the water required for the irrigation of local farmlands, hosts a significant heavy mineral sands deposit currently being mined by the Grande Cote Operations (GCO). As a result of variable rainfall and increased water abstraction, this shallow aquifer has recorded a continuous water level decline since 1970, with potential negative effects on both the social and economic development of the region. The mining of heavy minerals (zircon, ilmenite, leucoxene and rutile) at GCO is realised through conventional dredging techniques that require large volumes of water (up to 60,000 m3/d). The water pumped by the dredge to enable the extraction of the heavy minerals, infiltrates into the shallow aquifer, runs-off into the dredge pond or evaporates. The objective of this study is to evaluate a water balance that enables the provision of a permanent water supply to the dredge pond, whilst minimising the risk of flooding of the cropping depressions adjacent to the mine site or drying out of the farming wells. The hydrodynamic model implemented for this purpose was calibrated and tested during the first year of operation. The Root Mean Squared Error (RMSE) obtained for the calibration is approximately 0.52 m. The predictions indicate a requirement for the system to recover part of the tailings infiltration through dewatering boreholes. The quantity of recycled water is estimated at 16,000 m3/d on average. The model simulations show an additional water requirement, extracted from the deep Maastrichtian aquifer, varying between 23,000 and 28,000 m3/d to achieve the optimum pond water level.
文摘Gravity, magnetic and electrostatic separation methods allowed to obtain different titanium oxide concentrates (ilmenite, leucoxene, rutile) and different varieties of zircon concentrates (premium zircon, standard zircon, medium grade zircon standard) from Senegal’s heavy mineral sands. During mining separation, monazite, which is a paramagnetic mineral, was found in a non-negligible concentration of 0.57 wt% on average in the medium grade zircon standard which also contains 37.96 wt% zircon and 44.46 wt% titanium oxides. Magnetic and gravity separation tests were carried out on the Medium grade zircon standard (MGZS) to produce a monazite concentrate at Eramet Ideas laboratory. Magnetic separation at 1.5 teslas intensity resulted in the recovery of 94.8% of the monazite from the MGZS. Gravity separation also recovered 76.6% of the monazite from the MGZS. The combination of these two treatment methods can thus produce three concentrates from MGZS (a monazite concentrate, a zircon concentrate, and a titanium oxide concentrate).
