Integrated hydrogeological and chemical characterisation of thermal springs in Northern Oman

Study region Batinah Plain, northern Oman. Study focus Thermal springs constitute an important but understudied component of the hydrogeological system of northern Oman. The springs occur along the flanks of the Al Hajar Mountains in association with major fault and thrust structures. Field measurements, water chemistry, isotope compositions, and discharge estimates are combined with a simplified coupled groundwater flow and heat transport model to postulate circulation depths, flow mechanisms, and thermal regimes. New hydrological insights for the region The thermal waters are of meteoric origin and have undergone deep circulation before discharge. Hydrogeochemical facies are dominated by Na–K cations with variable anion compositions, reflecting contrasting lithological controls along flow paths through ophiolitic, carbonate and mixed sedimentary formations. Quartz geothermometry yields conservative reservoir temperature estimates of approximately 66–103 °C, implying circulation depths of roughly 0.4–1.9 km under the regional geothermal gradient of ∼19 °C/km. Numerical simulations demonstrate that such temperatures can be achieved through deep, fault-controlled groundwater circulation under normal geothermal conditions, without requiring magmatic heat sources or anomalous basal heat flux. Three end-member thermal spring system types are identified: ophiolite-hosted ultramafic systems, carbonate-dominated piedmont systems, and saline sedimentary systems, with a vauclusian spring representing a hybrid carbonate-hosted variant. The results indicate that northern Oman’s thermal springs are structurally and lithologically distinct system operating with a common regional thermal framework.