Investigating the Characteristics and Genesis of the Groundwater Resources Associated with Oil Shale Deposits in the Azraq and Harrana Basins, Jordan

Jordan lies in the northwestern part of the Arabian Plate. The structures and sedimentation were controlled by the tectonic evolution with respect to the configuration of the Arabian Plate. Upper cretaceous and Lower Tertiary Formations groundwater aquifers are associated with huge reserves of oil shale deposits in Harrana and Azraq Basins are evaluated in terms of water qualities and hydrochemical processes. The oil shale deposits are found within the Muwaqqar Chalk Marl Formation. The Muwaqqar Chalk Marl Formation represents the intermediate formation between the Lower Aquifer Amman Silicified Limestone and the overburden, which represents the overlying Upper Aquifers of Um Rijam Chalk and Wadi Shallala Chalk. This study aimed to improve the understanding of Muwaqqar Chalk Marl Formation as a sealing potential based on water quality and hydrochemical data of the different aquifers. Sixty water samples were collected from Amman Silicified Limestone Aquifer, High Grade Zone of Muwaqqar Chalk Marl Formation and from the overburden of Um Rijam Chalk and Wadi Shallala Chalk aquifers. The hydrochemistry of the collected groundwater samples represents a signature that reflects the sum of all physical and chemical processes and reactions that affected the water characteristics from the time of infiltration until reaching the aquifer The evaluation of the main hydrochemical processes affecting the groundwater quality were carried out by interpreting the ionic relationships and the water quality types using Piper and Durov diagrams. Comprehensive statistical analyses (Factor and Cluster Analyses) were conducted on the water quality parameters. The factor analyses can extract four factors from the water quality parameters of the Harrana wells Area-1 and for Azraq wells in Area-2. These factors are used to interpret the different geochemical processes affecting the groundwater quality parameters. Cluster analyses divided the Harrana wells into three groups. Cluster I included 26 wells with minimum mean concentrations of cations and anions, while cluster III included the wells with the highest concentrations in the water quality parameters. Cluster II included eight wells with intermediate concentrations. Azraq Area-2 wells are clustered into three groups. Cluster I includes seven wells with lowest water quality (highest concentrations); cluster II includes 12 wells and exhibits the lowest concentrations of ions and Cluster III includes five wells that show intermediate ions concentrations. The interpretation indicated that the primary factors controlling the groundwater chemistry of Azraq and Harrana appeared to be dissolution processes of the carbonate rocks containing traces of evaporitic minerals, ion exchange and reversal ion exchange processes. Moreover, the water quality in the study areas is not suitable for drinking purposes.