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

摘要

The Walbrzych-Klodzko sub-region forms the south-eastern part of the Polish Sudetic geothermal region. Warm springs up to 29℃ 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℃, which has been reduced by CO_2 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 CO_2 eruptions were observed. The results are less positive than expected. Artesian flow at a rate of 24 m~3/h has a maximum temperature of 35.8℃ while the amount of CO_2 produced is 160 m~3/h. The average thermal gradient does not exceed 2℃ /100 m and the estimated heat flow density is less than 50 mW/m~2. 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.).