Perspektywy poszukiwawcze złóż rud żelaza w utworach mezozoicznych Polski

Abstract

PERSPECTIVES IN SEARCH FOR IRON ORE DEPOSITS IN THE MESOZOIC FORMATIONS OF POLANDThe Mesozoic iron ores occur in Poland within sediments laid down under geosynclinal and platform conditions (Fig. 1).To the deposits of geosynclinal type belong those of the Tatra - Carpathian area.Siderites and manganese .ores of the Tatra area occur in mediterranean facies within clayey-carbonate series of the Pliensbachian and Aalenian. The ores have probably originated due to exhalation processes of submarine volcanism. On account of deep folding tectonics prospection possibilities are restricted from the economical point of view.In the Carpathians clayey siderites occur within clayey flysch sediments (Valanginian, Barremian and Palaeocene). The ores have been formed within shelf -zones of the Carpathian geosyncline. Because of permanent redeposition of ferruginous material, a formation of thicker deposits could not have taken place. For these reasons the ore-bearing series of the Carpathian flysch are not promising ones in further prospect ions for iron ore deposits.In the Mesozoic platform cover iron ore deposits occur only in central Poland. However, they are not found in the northeastern part of the country. The iron ores recorded from central Poland occur in the marginal area of the Święty Krzyż Mts., within the Middie Polish paranticlinorium, as well as in the Fore-Sudetic monocline. Here, may be distinguished ores formed under both marine and continental-conditions (Fig. 1). To the first type belong .ore deposits of Pliensbachian age, occurring in the northern part of the Pomeranian paranticlinorium, Dogger and Cretaceous deposits found in the Fore-Sudetic monocline and in the Middle Polish paranticlinorium, as well as ore deposits of the Fore-Sudetic monocline.To the ores formed under continental conditions belong those of the Rhaetian and Lias, occurring in the area of central Poland, in particular those of the northern marginal area of the Święty Krzyż Mountains.Deposits of marine type may be subdivided into two types, i.e. deposits formed in the shelf area round about the existing continents, arid deposits laid' down in the central portion of the basin, within the paranticlinorium. Among the deposits of the second type are distinguished deposits formed during the chemical sedimentation, mechanical sedimentation, as well as deposits of chemical-mechanical sedimentation. The deposits under consideration have been laid down as a result of washing-out of sediments and formed during the older sedimentary cycles. An uplifting of the sea bottom was due to the Kimmeridgian tectonics and formation of salt domes.As a result of analysis of materials from numerous bore holes areas have been selected for further prospections (Fig. 2). Most perspective are deposits of Pliensbachian age, occurring in the northern part of the paranticlinorium, sediments of the Dogger occurring within the marginal area of the Święty Krzyż Mts., and in the Fore-Sudetic monocline, as well as sediments of the Lower Cretaceous, which are found within salt domes in which oolitic-clastic ores occur.