Magnetic properties of the Bled El Hadba phosphate-bearing formation (Djebel Onk,Algeria): Consequences of the enrichment of the phosphate ore deposit |
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| Institution: | 1. Université de Liège. UR AGEs (Argiles, Géochimie et Environnements sédimentaires), B18. Département de Géologie Quartier Agora, Allée du six Août, 14, B-4000 Liège, Belgium;2. Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 7193 ISTeP, F-75005 Paris 05, France;3. Sorbonne Université, MNHN, UPMC Univ Paris 06, CNRS, UMR 7207 CR2P, F-75005 Paris, France |
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| Abstract: | To improve the enrichment of the Thanetian marine phosphate ore deposit from the quarry of Bled El Hadba (Djebel Onk, Algeria) before its exploitation, we first conducted a joint study using different techniques for comparison. These studies reveal that magnetic minerals play a significant role within the matrix of the central productive unit which is squeezed between two other units. Magnetic separation procedures show that there are some positive correlations between magnetic susceptibility and grain size fraction (80–250 μm). These dolomite-rich fractions are more clearly separated. Different tools were used to characterize the magnetic minerals (X-ray, microprobe, differential scanning calorimetry, thermogravimetric and thermomagnetic analyses). They show correlations between magnetic phases and the presence of associated magnetic minerals within the matrix or included in the phosphate ore deposit. They enabled us to distinguish a series of magnetic minerals (magnetite, hematite, maghemite, goethite, ilmenite, pyrite, iron–titanium oxide and titanium oxide sulphate) and to determine that Fe and Ti are prevalent in the separated fractions, following the same variation as Mg. The phosphorous (phosphate) rate is higher in the non-magnetic material, especially in the layers that are rich in dolomitic carbonates (upper and lower units), which could be trapped within the dolomitic matrix, while Magnesium (dolomite) is more important in the magnetic fraction. The separation of phosphate elements and dolomite carbonates is effective and therefore the ore can be enriched through magnetic procedures. Comparison between products enriched by magnetic separation, flotation and calcination showed important differences, chemically, economically and technically speaking. |
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