The role of lithology and tectonic structure in evaluation of karst, variation of discharge and quality of karst springs location in Abe-garm Qazvin area

The study area is located 90 Km south-west of Qazvin in the structure zone of central Iran. The rock units of the area are comprised of a vast variety of carbonate, clastic and pyroclastic rocks, with age of Cambrian to Oligomiocene, that have significantly outcropped in the area. This research is based on assessment of 369 springs around the Avaj-Abegarm region. 23 of them are karstic springs that are located in the limestone of Qom formation, Lar formation and the limestone of Cretaceous. The discharge variation of these springs is affected by lithology, degree of crushing and tectonic fracturing, degree of karstification of carbonate rock, amount of precipitation and type of aquifer in the region. Based on chemical analysis done on 5 samples that were taken from large karstic springs in the area, the type and facies of spring's water are sodium-bicarbonate and sodium-chloride. Hydrochemistry of karstic aquifers in the area is influenced by solubility of carbonate rock of Qom formation and Lar formation, surface recharge from Upper red formation mixed with upwelling of deep brine in Cretaceous carbonate rock that probably have hydrothermal geneses.