Kras a geneza złóż siarki w Polsce

Abstract

KARST AND THE ORIGIN OFSULPHURDEPOSITS INPOLAND

Summary

Recent studies by the present author on the geological structure and the origin of sulphur deposits inPolandas well as on karst in gypsum and in sulphur-bearing deposits have led to the following conclusions:

1. Karst development in gypsum occurred in two phases. The first phase took place just after the deposition of gypsum, i.e. during the formation of the Chodenice Beds, in the deeper parts of the basin; the second phase took place after the deposition of the lower series of the Pecten clays with Neobulimina longa, i.e. during the deposition of clays with Hanzawaia crassiseptata in the deeper part of the basin. The second phase continued till the Sarmatian.

2. Karst processes in gypsum were confined only to the emerging areas of anticlinal structures. The emergence of these structures occurred in two phases corresponding to the two phases of karst processes in gypsum.

3. Only those gypsum deposits which were subjected to both phases of karst processes could have been affected by biochemical and physico-chemical processes which led to the transformation of gypsum deposits into limestones sulphur. It was namely the karst processes in gypsum which facilitated the circulation of waters, as well as the formation of an aqueous basin in gypsum deposits, and opened the ways for the migration of bitumens.

4. An indispensable factor in the transformation of gypsum deposits into limestones with sulphur – till the very end of this process – is a continuous flow or movement of water so that karst caverns can be filled with water all the time.

On the other hand, when sulphur deposits have already been formed they must be completely covered with water if sulphur is to be preserved; thus the lack of the flow or movement of water – a basin which is not rejuvenated – is necessary here. In the case of the deposit in Tarnobrzeg, water was supplied by the River Vistula as a result of deep erosion, which extended as far as the Baranów Beds.

Such basic changes in the character of the water basin as those described above can be explained in the following way. Caverns which measure a few metres in diameter have been encountered frequently in gypsum deposits (borehole Posądza 40s). No caverns of that size can be found in the already exploited sulphur deposits in Piaseczno and Machów. This fact can be explained as due to differences in the resistance of rocks to compression. The resistance is large in gypsum, particularly in laminated gypsum; it is small in limestones with sulphur. The mass occurrence of brecciated sulphur ores shows that the top of the deposits collapsed and, that this happened at the time when the transformation of gypsum deposits into limestones with sulphur was quite advanced. In the final stage of the formation of sulphur deposits they were becoming compact; the caverns were compressed and dense sulphur was formed. The compactness of the sulphur deposit and the compression of caverns was undoubtedly caused first of all by the pressure of the ovelying mass of Sarmatian clays, which measured a few dozen metres in thickness. As a result of this, the collector, i.e. gypsum affected by karst processes, showed reduced permeablity. When the transformation of gypsum deposits into limestones with sulphur had been completed, the flow of waters from the surface was stopped; the deposit waters (not rejuvenated) preserved the deposit. Karst processes ceased gradually, and the role of karst as a deposit-forming factor ended.

Since the deposit became compact the evidence of the activity of two phases in the development of karst processes was almost completely destroyed.

Yet some unobliterated traces of different karst processes are frequently encountered in the exposed and exploited deposits in Piaseczno and Machów. These are small caverns in sulphur-bearing limestones, lined with dusty sulphur or sulphur crystals, limestone stalactites, limestone stalactites covered with sulphur crystals, concretion sinters, dome-like, fine, stalagmites with barite crystals or barite stalactites.

The youngest karst forms described here are the result of mining activity, which began when pumps for the purpose of draining the deposit were switched on. Huge amounts of mineral substances were pumped together with water: calcium sulphates, strontium sulphates, barium sulphates, calcium carbonates, and hydrogen sulphide. Thus the balance between the sulphur deposit and the solution of the above-mentioned saturating compounds was upset. The removal of mineral substances from the deposit led to the formation of small caverns, filled with fine sinters. The time when the presently observed karst phenomena originated is definitely determined by the fact that sinter forms – stalactites and stalagmites of calcium carbonates, strontium sulphates and barium sulphates – could not have been formed when the deposit was completely covered with water.