GEOLOGICAL ENVIRONMENT OF GEOTHERMAL WATERS IN THE PRODUCTIVE CARBONIFEROUS FORMATION IN THE UPPER SILESIAN COAL BASIN (USCB)

Abstract

For determination of geothermal waters occurrence conditions
in the productive Carboniferous formation in the Upper Silesian
basin there were analyzed: geological structure of the
Upper Silesian Coal Basin (USCB), forming of geothermal field
in rock mass, forming of hydrodynamic and hydrochemical
zonation as well as hydrogeological parameters. There is
shown in this paper that hydrogeological environment of the
productive Carboniferous formation is being formed under influence
of geogenic factors as well as mining exploitation.
The analysis carried out shows that geothermal waters
in the Carboniferous formation occur within the zone of the
little active groundwater circulation and the zone characterized
by very sluggisch groundwater flow. The depth of occurrence
could be even 700 m below the surface in the north -
eastern part of the USCB and about 400 m in the southern
part of it. These waters are mainly highly mineralized brines.
Results of investigation of chemical and isotopic composition
of discussed geothermal waters indicate generally a long time
of water stay in rock mass. In the stagnancy zone there occur
paleoinfiltrational waters of the Permian age and subordinately
of the Tertiary age. In the areas of active and deep and
long lasting mining exploitation geothermal waters within the
upper interval of their occurrence are mixed infiltrational - relict
waters. The observed tendency of diminishing values of
hydrogeological properties of rocks with depth under conditions
of rock mass isolation causes that the water-bearing
capacity of Carboniferous sandstones is generally low and it
is diminishing with depth.