Character of Surface Thermal Manifestations and Spring Waters at the Shargaljuut Hot Springs, Mongolia

摘要

The Shargaljuut Hot Springs (Mongolia) have been utilised for their medicinal qualities for more than 300 years. Thermal manifestations at Shargaljuut presently comprise a large area of effusively steaming ground, and numerous low-flow springs (<2 l/sec) that discharge near boiling (to 90.5 deg C), 8.2-8.7 pH, low Cl (<5mg/kg), weakly mineralised (<44mg/kg SiO_(2), <13mg/kg HCO_(3 (total))) waters. White to translucent opaline silica sinter covers rock surfaces around many of the hot springs, and exhibit a range of morphological characteristics. The presence of silica sinter is indicative of a high-temperature geothermal resource, although solute geothermometry indicate the springs are likely supplied from water reservoir of no more than approx130 deg C, whilst shallow drilling (to 50-60m) on the margin of the main thermal area for the Shargaljuut National Sanatorium tapped waters of approx80 deg C. The source of the geothermal energy is inferred to be conductive heat associated with the "South Khangai Hot Spot", which is transferred through the overlying Palaeozoic metasediments and igneous rocks to heat near surface meteoric waters.