ABSTRACT

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^–, SO₄ ^2– and Na⁺, respectively. Alkali ions, Cl^– and SO₄ ^2– are acquired through the dissolution of Halite (NaCl) and Gypsum (CaSO₄, 2H₂O). CI waters have depleted δ values for ¹⁸O and ²H, 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 ¹³C and ¹⁴C 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 ¹³C of –10 ‰. This means that these waters are derived from old precipitation whose features were totally different from the very scarce prevailing ones.

摘要

提迪凯尔特（In-Salah地区）的Continental Intercalaire（CI）地下水的特征是高盐度和离子浓度，高于可饮用性的最高标准。电导率范围为1470至6780μScm ^–1时，总溶解固体的含量为850至3390 mg L ^–1。它们的化学相是由氯为主^-，SO ₄ ^2-和Na ⁺分别。碱金属离子，氯^-和SO ₄ ^2-均通过岩盐（NaCl）中和石膏的溶解获取（的CaSO ₄，2H ₂ O）。CI水的δ值在¹⁸ O和² H，对应于冷端部件。这表明蓄水层非常均匀，这与东部次流域（大东方Er）的CI以及中东和利比亚其他地方的古水所观察到的相似。t分析表明，这些水的tri化作用都非常弱，这证明了这些水没有更新的特征。既δ ¹³ C和¹⁴ C对样品的十几测定也表明，CI地下水是旧的，与包含19000和35000年之间，平均年龄δ ¹³的Ç-10‰。这意味着这些水源于古老的降水，其特征与非常稀少的普遍降雨完全不同。