Hydrogeologiczne właściwości przestrzeni porowej dewońskich skał węglanowych w Górach Świętokrzyskich

Abstract

Hydrogeological properties of Devonian carbonate rocks matrix at the Holy Cross Mountains, central Poland.Summary. During research on the hydrogeological properties of Devonian carbonate rocks in the Holy Cross Mountains (Góry Świętokrzyskie) 141 samples of limestone and dolomite rocks were collected from natural outcrops and quarries located within the Southern (Kielecki) region of the Holy Cross Mountains (Fig. 1). Using standard laboratory methods open (interconnected) porosities, permeabilities (recalculated as hydraulic conductivity for water) and specific yield coefficients were determined. Open porosities of the limestones and dolomites are very low (tab. 1). Similar results were obtained with hydraulic conductivity testing, with slightly higher values in the dolomites than in the limestones (Fig. 2). The specific yield in all cases was zero. Thus, the studied limestones and dolomites are among the least porous, permeable and yielding rocks in Poland. The test sample population is characterised by having open porosities with a log normal distribution and hydraulic conductivities with an irregular (bimodal) distribution resembling a log normal distribution (Fig. 3). A slight corelation between the open porosity and the hydraulic conductivity was demonstrated (Fig. 4). This may indicate a greater portion of the smallest pores contributing towards the sum total open porosity under test conditions; in natural hydraulic conditions they would be inactive. Their contribution must be quite significant (the lack of specific yields), but variable (low relation between open porosity and hydraulic conductivity). Discussed are also possible correlations between the studied parameters and the rock matrix structure (classified as either pelite, sparite or crystalline — no correlation was demonstrated, Fig. 5), the occurrence of fractures (no correlation, Fig. 6) or the sampling locations (Fig. 7). Although it was not possible to show variability of parameters within particular tectonic structures, statistically significant differences were observed between structural features regarding the open porosity (but not for hydraulic conductivity).