The Continental Intercalaire groundwaters of the Tidikelt (In-Salah region, Algeria). Hydrochemical and isotopic features



Cherchali ME, Moulla AS, Amrous K, Ouarezki SA, Rezka A, Daas N.


Isotopes Environ Health Stud. 2021 Jun;57(3):217-235. doi: 10.1080/10256016.2021.1875221. Epub 2021 Feb 2.


The Continental Intercalaire (CI) groundwaters of the Tidikelt (In-Salah region) are characterized by a high salinity and ion concentrations higher than the maximum standards for drinkability. The total dissolved solids range from 850 to 3390 mg L(-1) for conductivities ranging from 1470 to 6780 μS cm(-1). Their chemical facies is dominated by Cl(-), SO(4)(2-) and Na(+), respectively. Alkali ions, Cl(-) and SO(4)(2-) are acquired through the dissolution of Halite (NaCl) and Gypsum (CaSO(4), 2H(2)O). CI waters have depleted δ values for (18)O and (2)H, corresponding to a cold end-member. This is an indication of a very homogeneous aquifer which is similar to what was observed for the CI in the eastern sub-basin (Great Oriental Erg) and for palaeowaters elsewhere in the Middle-East and Libya. Tritium analyses show that these waters are all very weakly tritiated, which is a testimony of the non-renewed character for these waters. Both δ(13)C and (14)C measured on more than a dozen of samples also show that CI groundwaters are old, with ages comprised between 19,000 and 35,000 years with an average δ(13)C of -10 ‰. This means that these waters are derived from old precipitation whose features were totally different from the very scarce prevailing ones.

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Link/DOI: 10.1080/10256016.2021.1875221