Major ions geochemistry and environmental isotope study of the nubian aquifer system, dakhla oasis, Western desert, Egypt

الملخص EN

Among the hydrochemical studies, the original marine solution of the NaCl type and the continental Na2S04 type of meteoric genesis, are the dominant water types in the Nubian sandstone aquifer.

The hydrochemical facies of sodium-calcium-chloride-sulfate are due to leaching, mixing, dilution processes, and removal of the marine solution by meteoric flows under oxidation-reduction potentialities.

The hydrochemical facies and marine-meteoric boundaries show that the groundwater flows from SW to NE across the Dakhla depression.

The determination of the saturation index (SI) indicated that anhydrite, aragonite, calcite dolomite, and magnesite are undersaturated with respect to the groundwater, and the minerals might dissolve.

The studies of stable isotopes reveal that the groundwater samples are plotted exactly along the sand-evaporation line (5D = 2.9* 5I80 - 54).

Radioactive isotopes show that tritium values fall below 2.6 Tu, which indicates that no recent infiltration water reached the aquifer due to high potential evaporation.

The application of carbon-14 dating indicates that the age of the groundwater is < 14 000 years B.R, i.e.

of post-pluvial time.