Wody termalne Sudetów

Abstract

THE SUDETES THERMAL WATERS

SUMMARY

Occurrence, origin and perspectives of prospection for thermal waters in the Sudetes are dealt with in the paper. The Sudetes are considered as a whole, nevertheless, particular attention has been given to the areas within the boundaries of Poland.
Thermal waters occurring in form of natural springs have been exploited for medical purposes since several centuries. They gave origin to such health resorts as Cieplice, Janske Lazne, Lądek, Velke Losiny and Bludov. In all the above localities the waters occur within crystalline rocks of Precambrian or Paleozoic age (Fig. 1.).
During recent years an increased demand caused a necessity to perform several boreholes in order to increase the water resources. Such drillings have been pierced at Cieplice, Lądek and Velke Losiny and gave positive even sensational results.
The thermal waters of the Sudetes are characterized by small general minerallisation (Table 1) (usually less than 1000 mg/l, in some cases less than 200 mg/1) and by increased fluorium content (up to 12 mg/l), silicium content (up to 120 mg/l H₂Si0₃), and sometimes by content of sulphuretted hydrogen (up to 5 mg H₂S+HS^-) and the tiosulphate ion as well as in some cases by increased radioactivity (up to 22 nCi/l). AImost all the waters show increased pH values (7.5–9). Nitrogen prevails in their gas composition (over 90%). Temperatures of waters from natural springs do not exceed 45° centigrade (Cieplice), whereas the maximal temperature of natural outflow obtained from the depth of 750 m in a borehole at Cieplice was 63°C (Table 2). Waters of temperature higher than normal occur in other localities in the Sudetes as well. They are more mineralized than those mentioned above which is connected with considerable amounts of CO₂ (Duszniki) or with occurrence of sedimentary rocks above the crystalline aquifer (Batnovice). Both chemical and gas composition of the thermal waters and the results of isotope investigations (D, ¹⁸O, ³²S, ¹⁴C, T) point to infiltration origin. The age of warmest water at Lądek and Cieplice that occur in natural springs has been defined as early Holocene and late Pleistocene (Table 3). Higher helium quantities in relation to nitrogen as compared to air composition indirectly prove the conclusion about infiltration of those waters at times mentioned above. Relative enrichment in helium proves long period of underground flow. Reckoning from SiO₂ content it may be assumed that only in such sites where it exceeds 50 mg/I the water has attained temperature higher than 100° centigrade during flow (Fig. 3). Such situation is to be noted at Cieplice and at Czerniawa where actually cold carbonated waters occur. Basing on the analysis of results of all investigations done so far and geological premises it may be concluded that much greater resources of thermal waters do occur in the crystalline formations of the Sudetes than those known up to date and exploited although no positive anomalies of heat flow density have been observed in the region. The zones in which such resources may be expected at depth not exceeding 2000 m are: the Karkonosze granite and its metemorphic cover, southwestern margin of the Central Sudetic depression and the Nysa Kłodzka Graben (the Kudowa granite, metamorphic formations of the Bystrzyckie and Orlickie Mts), the Złote Góry Mts, the Snieżnik Massif, the Hruby Jesenik Massif and some areas of the Foresudtic Block.