Mineral intrusion by geochemical modeling in the sandy textures. the case of the northern Algerian Sahara [Intrusion minérale par modélisation géochimique dans les textures sableuses des sols. Le cas du Sahara septentrional algérien]

The arid zones of the northern sahara are known for their characters of hydromorphic soils and halomorphie. they have always had with the scientific community a reputation of difficulty for the agricultural use. the area experienced in the summer period,concerned a natural soil sandy,supplied in depth by the groundwater of quaternary age. in order to lead to a physical and chemical characterization of this soil on the one hand,and the identification of the order of saline precipitation in the majority onthe other hand,the thermodynamic model geochemistry at 25°c (phreeqc model),has highlighted for three profiles the track neutral saline in recital the chlorine ion as a tracer stable. it has been shown in addition that from logarithm concentration factor (log fc ≤ 0.2),all the calcite are supersaturated,where their priority precipitation in the surface horizons: p1h0,p2h0 and p3h0. this calcium precipitation is confirmed by the values of ph > 8.5. it is essentially of the calcite (caco3),the magnesite (mgco3) and dolomite (camg (co3)2. regarding the solutions sulphated,precipitation in the majority are found mainly in the median horizons p1h2,p2h2 and p3h2 from fc = 1.24,corresponding to a crystallization of chloride ions from 280 ct/l and sulphate ions from 324 ct/l. among the soluble minerals,halite (nacl) is the mineral most close to the saturation.