Charakterystyka chemizmu wód piętra trzeciorzędowego w rejonie złoża siarki Grzybów - Solec Stary

Abstract

THE CHEMISTRY OF WATERS IN THE TERTIARY SEDIMENTS AROUND THE GRZYBÓW - SOLEC STARY SULPHUR MINE

Summary

The hydrochemical characteristics of Tertiary waters in the area of the Grzybów - Solec Stary native sulphur deposit are presented. The deposit is situated in the marginal part of the outer zone of the Carpathian Fore-Deep. The recharge of Tertiary aquifers is through the outcrops situated north of the deposit. The main water-bearing strata are the Lower Tortonian Lithothamnion limestones. Waters from the outcrop area reach the deposit both through the underlying Lithothamnion limstones and through the gypsum zone that surrounds the deposit. Analog computer data provided information on the distribution of waters in the Tertiary sediments. Under conditions undisturbed by solution recovery of sulphur about 550 cu m of water per day (i.e. about 12.5% of the total volume of water infiltrating the Lithothamnion limestones in the Sub-Quaternary outcrops zone) are supplied to the deposit area. A complete exchange of water in the deposit requires 200 to 1 300 years, excepting the Solec Stary area where, due to file direct contacts with the surface, the time of a complete exchange is reduced to less than twenty years. The ground waters recharging the Tertiary sediments in the outcrops zone are of the bicarbonate-sulphate-chloride-calcium type, while waters of the deposit horizon have a sulphate-calcium-sodium composition. The total mineralization is 0.75 g/l and 1 - 4 g/l (Tab. 3) respectively. It has been found that with distance from the recharge zone and consequently with the lower depth of circulation the concentration of Ca²⁺ SO₄^2- Na⁺ + K⁺ and CI^_ gradually increases along with the increase of total mineralization. The present studies confirmed the regularity, commonly observed in other deposits of the Fore-Carpathian area, that towards the deeper part of the fore-deep the infiltration hydrogen-carbonate-calcium waters gradually pass into sulphate-calcium and subsequently into chloride-sulphate-sodium-calcium waters. The waters occurring in the deposit area represent a slow exchange zone adjacent to the infiltration water area. The chemistry of the deposit zone waters reflects the flow dynamics and results from the thermodynamic-chemical and microbiological structure of the Tertiary water-bearing strata. The chemical processes in the deposit lead to a marked increase of hydrogen sulphide and free carbon dioxide in the circulating solutions. The processes are active in an almost neutral environment of slightly negative value of the redox potential. The presence of a relative high hydrogen sulphide and carbon dioxide concentration in the deposit area can be explained either by reduction of sulphates due to bacteria living on carbon contained in the hydrocarbons, or by sulphur hydrolisis in the reducing environment of waters related to the sulphur deposit.