Multigeological studies for illustration of the water-rock interactions in al Jaww plain, east of al ain area, United Arab Emirates (UAE)

Detailed petrographic and mineral investigations of quaternary sedimentsaccompanied with chemical analyses of groundwater were carried out in four aquifer wells located in Al Jaww plain, east of Al Ain area. The megascopic and microscopic examinations were conducted for 49 rock-cutting samples at different depths collected from these wells to investigate their detailed textural and compositional characteristics in order to evaluate the water—rock interactions as oneof the processes that release elements to the groundwater. X-ray diffraction analyses were also conducted for most of the bulk samples to determine the detailed mineral composition. Petrographically, there are four facies types recorded in thestudied aquifer sediments: ophiolite clasts conglomerate, ophiolite brecciated conglomerate, calclithite and lithic carbonate facies. Mineralogically, the aquifersediments consist of serpentine, calcite (major components), dolomite and plagioclase (subordinate), with minor contents of quartz, pyroxene, and amphibole. Groundwater analyses for the samples showed that the Ca²+ concentrations were increasing toward the west and this may be ascribed to the dissolution of carbonate contents of Neoautochthonous units (Asmari, Dammam, and Rus formations) anddiagentically formed as carbonate cements. This is supported by the presence of calcite as revealed from the mineral compositions of the rock-cutting samples. In addition, the Mg²+ concentrations for the groundwater samples were increasing toward the east and this might be related to the formation of serpentine and dolomite which are released to the groundwater due to the weathering of Allochthonous units (Sumeini Group, Hawasina Assemblage, Haybi Complex, and Semail Ophiolite) and diagentically formed. The vertical and lateral variations in their mineral composition percentages were also assessed to illustrate the distribution of mineral constituents percentages throughout the Quaternary aquifer.