Genezo i paleohydrogeologiczne warunki występowania wód zmineralizowanych na Niżu Polskim

Abstract

GENESIS AND PALAEOHYDROGEOLOGICAL CONDITIONS OF MINERALIZED WATER OCCURRENCES IN THE POLISH LOWLAND AREASummaryMost papers devoted to the occurrence of brines in the Polish lowland area emphasize that the origin of the mineralization of these waters closely related to the leaching processes of the Zechstein salt deposits the examinations made in the last years, particularly those on deep horizons, conducted to search for bitumen deposits have demonstrated that sedimentary waters play a somewhat more important role than it has previously been supposed. To explain the origin of these processes an attempt has been made at presenting the hydrochemical regionalization in the light of the palaeohydrogeological development of the Polish Lowland area. Two main hydrochemical zones have been distinguished: 1– up to 5 g/l of dry residue – characteristic of fresh and low-mineralized waters, and 2 – up to 50,0 g/l of dry residue showing the boundary of salt waters and brines. Four ranges of depth have been distinguished for the first hydrochemical zone: 1000–1500 m, 500–1000 m, 200–500 m, and 0–200 m (Fig. I). The maximum thickness of the freshened water zone is observed to appear within the Mazury–Suwałki elevation, in the eastern part of the Podlasie depression and in the northern marginal area of the Świętokrzyskie Mts. anyicllnorium.The succesion, shallower ranges of depth gradually move westwards and north-westwards, as follows Zoned 500–1000 m covers the north-western slope of the Mazury–Suwałki elevation, the westerly part of the Podlasie depression, the south-western part of the Peri-Baltic syneclise, a considerably part of the marginal synclinorium and the Łódź– Miechów syncliorium, as well as the north-eastern part of the Silesian-Craców monocline. Zone of 200–500 m – occurs in the marginal area of the Carpathian foredeep, in the north-eastern part of the Fore-Sudetic monocline, and almost in the entire area of the north-western part of the Polish Lowland.Zone 0–200 m – occurs in the south-western part of the Fore-Sudetic monocline, fragmentally within the Middle-Polish anticlinorium (salt plugs) and in a belt of the western and partly central sea-shore.The second hydrochemical zone (up to 50 g/l) has been presented in three ranges of dept up to 1000 m, 1000–1500 m, and below 1000 m, which for the most part may be correlated with the subdivision of the low-mineralized waters.The paleohydrochemical analysis – of the development of the Polish Lowland area allows the authors to distinguish here two main hydrochemical provinces:1 – eastern province (area of the East-European platform) and 2 – western and north-western province (the remaining areas). The first province low-mineralized waters prevail reaching fairly deep horizons (1000–1500 m), whereas in the second one – strongly mineralized waters occur rather at a shallow depth, at places even in the near-surface zone.The Platform area of the Polish Lowland was characterized by the predominance of denudation, leaching and removal processes of mineral particles. In the remaining areas accumulation processes and formation of sedimentary waters prevailed as a result of marine transgressions. These conditions were favorable for both the formation and the preservation of strongly mineralized waters of sedimentary type and of various metamorphism degree at shallow depths. Salt plugs no doubt affected also the composition of waters in the western province (within the active circulation zone), since the process of salt leaching was responsible for a secondary salting of shallow waters. In the stagnation zone, this influence was insignificant.Within the eastern province the main zones of freshening were developed at the post-Cretaceous time. This process was most intensely expressed during the Miocene and Quaternary times.