Investigation on concentration of heavy and rare elements in active hydrothermal fluids in the geothermal field, south of Mount Sabalan, Ardebil province, NW Iran

The geothermal field at the south of Mount Sabalan is a part of the geothermal system of the Sabalan volcano region wherein manifestations of young volcanic activities including hot springs and surficial steams are observable. The surficial hydrothermal fluids in this area show maximum temperature of 77°C, pH range of 6.4-7.4, and maximum TDS values of 7006 mg/l. Generally, these waters are divided compositionally into two groups. The first are mainly Na-Cl waters while the second are chiefly Ca-Na-HCO3 waters. The rare and heavy elements in these fluids are principally boron, lithium, rubidium, cesium, arsenic, and mercury whose maximum abundances are 33511, 14265, 3418, 10366, and 5 ppb, respectively. Considering the lithologic units in the area, vast hydrothermal fluid activities, and wide-spread alteration zones, boron-bearing minerals were regarded to be as the major sources of this element, which was leached and transported by geothermal fluids. Boron concentration in these fluids is controlled in part by fixation in clay minerals. Further considerations in geochemical behavior of the rare and heavy elements in this geothermal field demonstrated that lithium and rubidium were absorbed by quartz and clay minerals, respectively at temperatures