Water separated from Fluid samples (centrifuged at 4000 rpm for about 20 min.) originating from 3 deep boreholes (from depths of 3254 m, 3181 m and 3012 m) of the Risha gas field and of a normal shallow groundwater of the Mudawwara area in Jordan were analyzed for their chemical composition and for 36Cl by AMS. According to the chemical composition the analyzed waters can be characterized by two groups, a first one of waters of low to moderate chloride contents and total mineralization as groundwater of meteoric origin, and a second one as brine of very high mineralized waters with very high sodium, potassium, calcium and strontium cationic contents and also very high chloride and bromide anionic contents. These sampled fluids can be characterized as brine, of origin by evaporative concentration of fresh water (as for lower part of Jordan River or arid zone lakes (as lake Kinneret, or terminal lakes as the Dead Sea) or as formation waters of deep basin sedimentary origin (as remaining pore water of mainly marine origin).These different possibilities of origin of the investigated ground waters can be checked by the corresponding ion ratios (in meq/l): Considering the Na/Cl - ratio it results that mainly all investigated groundwaters including the low mineralized groundwater and the high mineralized waters originating from deep fluids yield ratios which are much closer to the Na/Cl ratio of the rain water sample (originating from Amman airport station) than to the ratio of the Dead Sea water or a deep sedimentary brine (referring to the Gulf of Mexico Brine, as reported in Kaharaka and Carothers, 1986). But if considering Br/Cl ratios of the high mineralized waters of the deep fluids values coinciding to the values of the sedimentary brines of the Gulf of Mexico result. But a quite different Na/Cl and Mg/Cl ratios results for the shallow groundwater of the Ghusan well (originating from the Safawi area), which may indicate a recharge by already evaporated surficial water. The resulting residence times of the chloride according to the measured 36Cl results depend strongly on the assumed evolution type and assumed flow path. For the low mineralized groundwater only a unique evolution from a low mineralized groundwater of by recharge is considered. It results a residence time between recent and 220'000 years. For the deep and high mineralized groundwater the resulting residence times are strongly dependent on the modeled evolution path.
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