Uranium isotopes in groundwater from the continental intercalaire aquifer in Algerian Tunisian Sahara (Northern Africa)

Paleo water–rock interaction determined through isotopic tracing (Sr, O, C, U) in fracture-fill minerals: Evidence from the Vienne granitoids (France)

“…In the lower zone (400-900 m), a deficiency of 234 U relative to 238 U (Fig. 10), suggests alpha recoil that enhances 234 U solution from the mineral surfaces to the fluids, as previously evidenced for example in the Continental Intercalaire aquifer (a huge fossil complex aquifer system situated in the northern Sahara) by Chkir et al (2009). Deep conditions (reducing environment inducing U-precipitation, long residence time of groundwater, etc.)…”

Identification of dominant hydrogeochemical processes for groundwaters in the Algerian Sahara supported by inverse modeling of chemical and isotopic data

“…It is estimated at present that this sea did not reach Ouargla and transgression stopped at the edge of the bowl (Furon, 1960;Lelièvre, 1969). The basin is carved into Mio-Pliocene (MP) deposits, which alternate with red sands, clays and sometimes marls; gypsum is not abundant and dated from the Pontian era (during the MP) (Cornet and Gouscov, 1952;Dubief, 1953;Ould Baba Sy and Besbes, 2006). The continental Pliocene consists of a local limestone crust with puddingstone or lacustrine limestone (Fig.…”

“…where α is the fractionation factor during evaporation, ≡ −1000 × (1 − α) is the enrichment factor and k is a constant (Ma et al, 2010;Chkir et al, 2009). CI and CT waters are better separated in the semi-logarithmic plot because they are differentiated by their chloride content.…”

“…-In the middle, the Complexe Terminal (CT) (Cornet and Gouscov, 1952;UNESCO, 1972) is the most exploited and includes several aquifers in different geological formations. Groundwater circulates in one or the two lithostratigraphic formations of the Eocene and Senonian carbonates or in the Mio-Pliocene sands.…”

Uranium isotopes in groundwater from the “Jeffara coastal aquifer” (southeastern Tunisia)

“…Aquifer classification in term of U content mainly refer to 1 ppb and 10 ppb as U-content limits to distinguish aquifer types: oxidized aquifer on "normal" U-content strata (values between 1 and 10 ppb); oxidized aquifer on enhanced U-content strata (values higher than 10 ppb) and reduced aquifer on low U-content strata (values lower than 1 ppb) (Cowart and Osmond, 1980;Roback et al, 1997;Bonotto and Andrews, 2000;Chkir and Zouari, 2007;Chkir et al, 2009). …”