The role of active geological structures in forming hot springs in Ramsar, Iran

Abstract

The hot springs of Ramsar, Iran are located at the northern zone of the Central Alborz Mountain Range along the Caspian Fault. Ramsar is a well‐known area with amongst the world's highest levels of natural radiation. Due to the local geology, which includes high levels of radium in rocks, soils, and groundwater, Ramsar residents are also exposed to high levels of alpha activity in the form of ingested radium. Nine springs were selected from the hot springs of Ramsar for this research, and water samples were tested to find the amount of dissolved materials and elements. Analysis of the results suggests that the hot springs of Ramsar originated from the sea. The results indicate that coincident with subduction of the southern Caspian basin and obduction of the Central Iranian crust over the southern Caspian crust, saline seawater reaches fracture zones of the Caspian Fault where it is heated due to mixing with radioactive materials and release of radon as a result of activity of the faults and its decay into radium. Then it migrates along the Caspian thrust faults and forms hot springs originated from regional surface waters of Ramsar. Those hot springs located next to thrust faults were the result of collision, and the origin of neighbouring cold springs is karst.