Identifying the Source and Generation of Thermal Groundwaters based on Stable Isotopes and Rare Earths – the Case of the Lower Yarmouk Gorge Artesian Wells.

Abstract:

Along the Lower Yarmouk Gorge, thermal groundwaters with varying chemical and isotopic signatures emerge from Cenozoic Limestones. The bordering semiarid Golan and Ajloun Heights host fresh and variable tempered groundwaters in Cretaceous and Cenozoic strata. Sources and mineralisation of these groundwaters are derived from mutual discussion of d²H, d¹⁸O and d³⁴S, major elements, rare earth distribution patterns and the (hydro)geological setting. Positive shift of d¹⁸O and d²H occur due to evaporation before replenishment and the interaction with basalts. Major infiltration areas for Golan Heights are the limy foothills of the Mt. Hermon and for the Ajloun Heights the Plateau itself. To a less degree, precipitation infiltrates also the basaltic catchments. Groundwaters are mineralised by water/rock (i) variably altered limestones by diagenesis, (ii) evaporates and seawater brines enclosed in limestone matrix and (iii) locally occurring basaltic intrusiva. In the Yarmouk Gorge, a deep-seated brine of the Ha’on type ascends and mixes with the fresh shallow groundwater.

REY and isotope fingerprints prove that water from the Syrian Hauran Plateau is recharging springs and wells in the lowermost Yamouk Gorge. Although capping wide areas, the basaltic cover of the Golan Heights is of minor importance for recharge of the underlying A7/B2 aquifer, which becomes recharged at the foothills of Mt. Hermon and gets confined southwards, leading ibid. to ascension of water into the basaltic cover.

Anomalous heat flux near the Yarmouk gorge and locally in the western escarpment of the Ajloun may be produced by ascending fluids from greater depth and/or by basaltic intrusions.