Hydrogeologic framework of the Maku area basalts, northwestern IranSchéma hydrogéologique de la zone basaltique de Maku au nord ouest de l’IranEsquema hidrogeológico del área basáltica de Maku en el Noroeste de Irán伊朗西北部马库玄武岩区的水文地质结构ويژگيهاي هيدروژئولوژيكي بازالتهاي منطقه ماكو، شمال غرب ايرانQuadro hidrogeológico dos basaltos da área de Maku, noroeste do Irão

The Maku area in northwestern Iran is characterized by young lava flows which erupted from Mount Ararat in Turkey. These fractured volcanic rocks overlie alluvium associated with pre-existing rivers and form a good basalt-alluvium aquifer over an area of 650 km2. Groundwater discharge occurs from 12 large springs, ranging from 20 to 4,000 L s−1, and from some extraction wells. Permian and Oligo-Miocene age limestones along the northern boundary of the Bazargan and Poldasht Plains basalts are intensively karstified and groundwater from these high lands easily enters the basalt-alluvium aquifers. The transmissivity of the basalt-alluvium aquifer ranges from 24 to 870 m2 d−1, indicating heterogeneity. Groundwater of the aquifer is a sodium-bicarbonate and mixed cation-bicarbonate type and the concentration of fluoride is higher than the universal maximum admissible concentrations for drinking. In order to determine the chemical composition and identify the source of the high fluoride concentrations in the groundwater of the basaltic area, water samples from the springs, wells and rivers were analyzed. The results indicate that the high fluoride water enters the study area from the Sari Su River.