New findings in the Walbrzych–Klodzko geothermal sub-region (Sudetes, Poland)

The Walbrzych–Klodzko sub-region forms the south-eastern part of the Polish Sudetic geothermal region. Warm springs up to 29 C have been found at Ladek. At Duszniki some springs and shallow boreholes produced or produce carbonated water, at a temperature close to, or slightly exceeding, 20 C, which has been reduced by CO2 expansion. The existence of a positive geothermal anomaly was assumed in this area. A 1695-m deep borehole has recently been drilled at Duszniki to supply thermal water for medical treatment and space heating. Below the Quaternary formation (6-m thick) the borehole penetrated micaschists and gneiss of the Proterozoic (Lower Paleozoic?). In zones of tectonic disturbance water inflows and strong CO2 eruptions were observed. The results are less positive than expected. Artesian flow at a rate of 24 m3/h has a maximum temperature of 35.8 C while the amount of CO2 produced is 160 m3/h. The average thermal gradient does not exceed 2 C /100 m and the estimated heat flow density is less than 50 mW/m2. As no positive heat flow anomaly has been found, the temperature of the water is ascribed to its deep circulation through fault zones. Its recharge area may be as high as 850 m (in the Bystrzyckie Mts.), whereas stable isotope analyses suggest an altitude of 1000 m (Orlickie Mts.). # 2003 CNR. Published by Elsevier Ltd. All rights reserved.