Hydrochemical characteristics of thermal water reservoir in ladek-zdrój˛ in light of research into the borehole lzt-1—the deepest borehole in the sudetes (SW Poland)

Abstract

Ladek-Zdrój˛ is situated within the tectonic unit of the Ladek-Śnieżnik˛ metamorphic complex. Thermal water is captured by five springs and borehole L-2. These waters are characterized by TDS content in the range of 160–230 mg/L and predominance of HCO−3 (15–100% meq), SO 2+4 (10–36% meq), and Na+ (57–91% meq) ions. Increased concentrations of radon, hydrogen sulfide, and fluoride ions (7–13 mg/L) determine the medicinal properties of these waters, classified as thermal waters of Na-HCO3-(SO4), F−, H2 S, Rn type, with temperatures of 18 to 30◦ C and 41 to 45◦ C in springs and in the L-2 borehole, respectively. At the turn of 2018 and 2019, a new borehole LZT-1 was drilled in the area of Ladek-Zdrój.˛ It captured thermal waters with a temperature of 37.4◦ C at the outflow. The water temperature at the bottom of the heated borehole reached about 59◦ C. The lithology of rocks found in the recharged areas implied that the Ca2+ ions present in the studied waters originated from pyroxenes, amphiboles, calcite, calcium plagioclases, and fluorite. As for Na+ and K+ ions, they originate from sodium plagioclases, microcline, and orthoclase. The probable deposit temperature of waters from this borehole was estimated with the use of chemical geothermometers, as ranging from about 87◦ C to 97◦ C.