Hydrogeochemistry of hydrothermal waters from Salams magma chamber: Case study of Isti Su hot spring, NW of Iran

The Isti Su hot spring is located in southeast of Salmas, in Western Azerbaijan, Iran. The area is a small part of Sanandaj-Sirjan geological zone which hosts many hot springs. The magma chamber of Salmas region is the main heat source of the hot springs in Isti Su area. Abundant rainfall and relatively long duration of snowfall as well as several deep faults in the area create the best conditions to have several hot springs in the area. The host rocks of the area are sedimentary and metamorphic rocks of Cambrian to Recent sediments which are intruded by several granite and ophiolite bodies. Several hot springs have been formed in the vicinity of these plutonic to sub-volcanic bodies. The Isti Su hot spring is one of the most typical hot springs of the Salmas region. Eight samples were collected from the study area. In order to investigate the seasonal changes in the field and chemical parameters and to measure trace element concentrations in dry and wet seasons, springs were sampled twice in May and November. Temperature, pH and electrical conductivity (EC) of the water samples were measured on-site. Temperatures of the selected samples range from 26.3 °C to 38.5 °C. The pH values of the samples vary between 6.4 and 7.5. TDS contents range from 9200 to 1790 mgL^-1. The results of geochemical analysis show that the As, Li, Fe, Hg, Na, and Cr are not more than WHO’s standard level. As and B are two times more than WHO’s standard level. The As and B concentrations in the hydrothermal and geothermal solutions rise higher than its standard level. WHO’s recommended As level for drinking water is 0.01 mg/l^-. The Na-SO₄-HCO₃ triangular diagram shows that the samples are of HCO₃ and Na types. Open skin scars, gangrene, malignant cancers and environmental problems are among the consequences of high concentrations of As and B. The high content of As and B in water of this hot spring can be harmful to the environment and people of the area.