Geochemistry of geothermal springs in the Sabalan area, Azarbydjan-Iran

Abstract

The Sabalan area, located in Azarbydjan, is the most promising geothermal area in northern Iran. This area consists of three geothermal fields located in the northern, eastern and southern parts of the Sabalan central volcano. Geothermal investigation in the northern part of Iran, including the Sabalan area, was carried out by ENEL thirteen years ago. After a ten years break, the Ministry of Energy and Electric Power Research Centre (E.P.R.C.) resumed geothermal investigations in this area in 1993. In this study, attempts are made to interpret the available chemical analyses of spring waters in view of new geochemical interpretation knowledge and techniques. The chemical composition and small variation in D in the thermal springs of the Sabalan indicate local recharge at high elevation. Correlation between Cl and B indicates a common source for the three geothermal fields. Linear variation of Cl with B, Na, K, SiO2 and 18O indicates mixing of geothermal fluid with shallow ground water. The significant 18O positive shift indicates exchange with the rock matrix at high temperatures. Application of various geothermometers and mixing models yields temperatures in excess of 200°C in the deepest part of the geothermal reservoir.