Słone wody w osadach permskich północno-wschodniego obrzeżenia Górnośląskiego Zagłębia Węglowego

Abstract

Salt water in Permian sediments on the north-eastern border of the Upper Silesia Coal Basin In the mine galleries of a certain zinc-lead ore mine in Olkusz region (to NW of Cracow) carved in the roof portion of the Permian series, at the depth of 150 m, the waters of chloride type mineralization nearly 22 g/1 were found for the first time in 1974. The authors have initiated studies in matter of their chemical composition, their occurrence conditions and their distribution regularity. In the hydrogeological profile of the investigated region there occur three waterbearing horizons: Quaternary (fluvioglacial sands), Triassic (carbonate strata of the Middle Muschelkalk, Lower Muschelkalk and Rhoetian) and Paleozoic (carbonate series of the Lower Carboniferous and Devonian). An insulating series of Keuper clay separates Muschelkalk from Quaternary. In the Triassic substratum there occur the low permeable Permian deposits about 200 m thick. They are the continental, piedmont, diastrophic sediments formed in arid climate represented as porphyry-carbonate conglomerates with marly-sandy-tuffaceous matrix. T he autors’ investigation into the chemistry of water seeping out from mine workings walls or flowing out from underground bore-holes included: total dissolved solids amount field measurements applying resistivimeter, chemical analysis of these waters, heavy metals content field determination, trace elements spectrophotometric determination and tritium determination. Besides pore-solutions were squeezed out of the rock samples and water extractions of rock samples were prepared. Chemical analysis of both types of solutions were done. Water and rocks were sampled in the faces of mine galleries 6000 m long. It rendered possible to take occasion to observe regularity in changes of investigated chemical water composition. In relation with the general mineralization the investigated waters were divided into four groups: fresh waters (total dissolved solids content: M <10 g/1), low mineralized waters (1 g/l < M < 5 g/l), moderate mineralized waters (5 g/l < M < 10 g/l), and high mineralized waters (M > 10 g/l). The first group represents the waters of the mixed type, they are significantly different than the other groups as far as the proportion between anions and cations is concerned. The waters of the second group are of Na-Cl-SO(4) and Na-SO(4)-Cl character, but a certain number of samples indicate the higher content of HCO(3) and Mg ions. So they exhibit certain features of waters of Glauber type (Na-SO(4)) or of bitter waters rarely occurring in Poland. The waters of the third group are Na-Cl-SO(4) type. The waters containing more than 10 g/1 of total dissolved solids are typical sodium-chloride solution with up to 77 mg/1 of bromine content and up to 3 mg/1 of iodine content. Mineralization and chemical composition of pore solutions are practically the same as of gravity-ground waters. The investigation indicated the pronounced regularity in spatial distribution of waters of different mineralization. The vertical hydrochemical zonality is represented in the gradual water mineralization increase along with the depth below Triassic sediments bottom (Fig. 9, 10). In the neighbourhood of faults and in fissured zones the mineralization of waters gradually decreases. This phenomenon is so regular that it could became the base for the determination of the actual distance between the face of the mine heading driven towards the fault and this dislocation. Authors discuss the origin and the possible mechanism of the observed hydrochemical zonality formation. They consider that the investigated waiters are neither burried Permian sedimentary waters nor younger marine infiltration waters, nor products of NaCl concentration of surface and underground waters taking place in the conditions of hot and arid climate of the Permian. From the authors’ point of view the principal source of water mineralization is to be found in older marine sediments underlying the Permian series. The characteristic shape of the curve representing the changes of chemical water composition together with depth (Fig. 10) is related on the one hand with the diffusive and convective salt penetration from the deeper parts of the geological profile and on the other hand with the removal of these salts by fresh water penetrating from the surface through the high permeable overlying Triassic formation by the same mechanism.