Groundwater recharge to ophiolite aquifer in North Oman: constrained by stable isotopes and geochemistry

The current study employs geochemical and isotopic tools to understand hydrochemical and recharge processes characterizing ophiolite aquifer in North Oman in conjunction with the Hajar Super Group (HSG) aquifer. A total of 57 samples were analyzed for major ions and stable isotopes ²H and ¹⁸O. The geochemical composition of groundwater indicates that water–rock interaction and mixing are the main processes controlling groundwater chemistry. Groundwater in the HSG is characterized by carbonate minerals dissolution contrary to the groundwater in the ophiolites where silicates dissolution dominates. This results in differences in the groundwater chemical composition in the two systems. Isotopic characteristics of precipitation collected during the study period indicate two main moisture sources from the Indian Ocean and the Mediterranean Sea. Groundwater δ²H and δ¹⁸O values suggest two recharge sources to the ophiolite aquifer: lateral flow from the HSG and direct infiltration. Recharge from direct infiltration in the highlands, which is depleted in δ²H and δ¹⁸O, retains the same isotopic signature of precipitation, whereas that in the low land substantially reflects an evaporation effect.