Sources of mineralization and salinization of thermal groundwater of Jordan

Abstract

AbstractAccording to spider patterns five different types of thermal groundwater are distinguishable in Jordan. Each spider diagram comprises groups of elements which characterise soluble minerals of the aquifer such as halite, calcite, and gypsum, and leachable fractions of trace elements such as B, Ba, Br, Y, Cs, Rb, and U. In Jordan, mineralization of groundwater is largely controlled by dissolution of halite, carbonates, gypsum, and leaching diverse K‐bearing minerals. Caused by interaction with Neogene basalts, limestones are silicified and mineralogically altered. Groundwater from these aquifers significantly differs in composition from those of the unaltered limestone aquifers. The benefit of spider patterns is that they visualise (i) chemical differences in groundwater from essentially similar aquifer rock such as young, old or thermally altered limestones and (ii) chemical similarities of groundwater produced from different geological formations. In contrast to spider patterns, ionic ratios widely overlap and do not unequivocally allow grouping of groundwater. δ34S(sulfate) varies between –4 and +29 ‰. Low values prove the presence of oxidised sulfides either of igneous origin or from sedimentary rocks. The spread of δ34S is caused by mixing with marine sulfate. All analysed water from Paleozoic rocks is replenished from younger aquifers. Considerable transaquifer flow exists more or less all over the Jordan territory. Salinization of sandstone‐bound water along the rift escarpment is caused by a Na+‐K+‐SO42–‐HCO3– brine, whereas the wells Al Umari 1 and Wadi Araba 5 are affected by the presence of a Ca2+‐Cl– brine.