| Heavy-mineral sand-deposits are the main sources for the world supply of rare metals as zirconium and titanium. Concentrations of these minerals are known to occur in beach and dune sands. The economic importance of the Black Sands is attributed to their contents of industrial minerals such as ilmenite, hematite. magnetite, zircon, garnet and monazite. These deposits usually may visually be recognized by a darker colouring of the sands.Since heavy-mineral concentrations are often found in beach ridges it is generally accepted that the concentration took place by the selective removal of the lighter minerals such as quartz during erosion along a sandy coast. The presence of heavy minerals in beaches and dunes can therefore be used as an indicator for coastal development processes (erosion).The studied sector is situated on the Atlantic coast of Morocco about twenty km to the Northeast of El Jadida, near of Azemmour town. It belongs to the Moroccan Meseta crossed by the Oum Er-Rbia river. Climate, geomorphology, hydrology and geology of the Oum Er Rbia basin control the morphology and the sedimentation on this area. The climatically regime of this basin is under the influence of a Mediterranean climate of semi-arid type.Sand samples (thirty) were collected along of perpendicular beach profiles to the shore (river and sea) spaced of 50m to left of the river and 200m along of the beaches in order to examine the sorting patterns of heavy minerals that develop during cross-shore and alongshore sediment transportGrain-size analysis quartz morphology, heavy mineral and CaCo3 content analyses were performed on all the samples. The heavy fraction was separated from the light fraction by the gravity separation method. Selected samples for the analysis include the polished thin-sections prepared for modal analysis and isomagnetic separeted fractions were investigated. |
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