Geochemical Characteristics of the South Khorasan Geothermal Fields, E-Iran
Mohammad Reza RAHMANI
South Khorasan Province hosts several low-temperature geothermal prospects include Ferdows, Lut, Dig-e Rostam, Kandegan, Morteza Ali and Gazik. Thermal springs are the most visible manifestations of geothermal systems in this province. Thermal springs have temperatures between 31.8 and 51.9 °C. The Na-K-Mg triangular diagram shows that the thermal waters plot in the area of immature waters (except for Ferdows and Lut waters that they plot on the border between immature and partially equilibrated waters) with a relatively high Mg content, indicating that the geothermal waters have possibly a high proportion of cold groundwater. According to a Cl-Li-B ternary diagram, all the samples have high Cl relative to Li and B suggesting that they are from old hydrothermal systems. The Na-K-Mg-Ca diagram illustrates that all the thermal waters plotted far from the full equilibration curve indicating these waters are not fully equilibrated or high degree of mixing with cold groundwater and or re- equilibration. The Cl-SO4-HCO3 triangular diagram shows that the thermal waters from Kandegan and Gazik plot in the peripheral waters area, while Ferdows, Dig-e Rostam and Lut waters lie in the field marked “volcanic waters” and only Morteza Ali water plots between peripheral and volcanic waters, which might be an indication that it is combined water. Characteristics of thermal waters indicate that the common geothermometers involving Na, K, Ca, and Mg are unlikely to be applicable to these waters, therefore reservoirs temperatures have been calculated based on thermal spring samples using the chalcedony conductive and quartz conductive geothermometers as 57-89 °C, 55-86 °C, 72-102 °C, 85-114 °C, 23-55 °C and 23-55 °C for Lut, Ferdows, Dig-e Rostam, Kandegan, Gazik and Morteza Ali respectively. The temperature obtained from chalcedony geothermometer (23 °C) for both waters from Gazik and Morteza Ali is not valid as it is lower than spring’s temperature.
|        Topic: Geochemistry||Paper Number: 14041|