Major Polish rock salt deposits are related to the Miocene and Zechstein halite formations.
Deposits of the Miocene formation are situated in a belt extending from the Silesian region to Wieliczka and Bochnia and further eastwards up to the Poland-Ukraine border and running along and close to the present-day frontal overthrust of the Carpathian Mts on their foredeep. In the Wieliczka area the salt was produced from the Middle Ages right through into the 19th century. Exploitation of these deposits ended in 1996 when salt mining was phased out in the Wieliczka mine. The proven resources of Miocene rock salt deposits are estimated to be over 4.36 billion tonnes, accounting for 5.13 % of domestic resources. However, geological structure of these deposits is very complex due to intense folding (except for the Rybnik-Żory-Orzesze deposit which is situated in a tectonic trough). That complexity of geological structure along with markedly varying salt quality and high risks of water flooding and methane inflow to mining works were the reasons why further mining of these deposits became practically uneconomic. The Wieliczka mine was included on the UNESCO World Heritage list in 1978. Nowadays the Wieliczka and Bochnia mines are great tourist attractions and recreation centers.
The Zechstein halite formation is at present the major source of mined salt in Poland. The salt-bearing series are distributed throughout two-thirds of area of the country, mainly in the Polish Lowlands. In the Late Permian these areas were occupied by evaporitic epicontinental basin which was the place of accumulation of salt sediments with total thickness of over 1,000 m. Bedded rock salt accumulations were explored down to 1,000 m depth in marginal parts of the basin and in the Łeba Elevation and the Fore-Sudetic Monocline. Resources of these deposits are estimated at almost 25 billion tonnes, which accounts for 29.42 % of domestic salt resources. In turn, in axial part of the basin (Central Poland) the salt-bearing series are buried at depths up to 7 km, locally rising almost to the surface in salt dome- and pillow-like structures. The salt structures occur in a belt stretching from Wolin in the northwest to the vicinities of Bełchatów in the south-east. Deposits of rock salt and potassium-magnesium salt were explored and proved in a number of the shallowest of these structures. Proven anticipated economic resources of deposits related to the salt structures are estimated at more than 55.6 billion tonnes, which accounts for 65.45 % of domestic salt resources. Exploitation of the latter deposits gives 100 % of the current domestic production of salt (excluding exploitation of rock salt deposit – within overburden of copper deposit Sieroszowice).
Large bedded rock-salt deposits were also explored in the overburden of the Sieroszowice and other copper ore deposits in the Fore-Sudetic Monocline. In that area, some production of rock salt is already carried out within the frame of surveying and development works.
Bedded rock-salt deposits are explored down to the depth of 1,200 m, providing that the deposit series (including partings) is at least 30 m thick and minimum weighted mean of NaCl in the deposit series and partings equals at least 80 %. In accordance with the Polish regulations, salt deposits related to the dome and pillow salt structures are explored down to 1,400 m, providing that the distance between top surface of salt deposits and salt mirror is not smaller than 150 m. The remaining requirements are the same as in the case of the bedded deposits. At present the salt deposits begin to be treated as geological objects especially advantageous for construction of underground facilities for storage of oil and natural gas and liquid fuel (such as already operating Mogilno II and Góra) and safe disposal sites for hazardous materials.
The anticipated economic resources of rock salt (excluding those within protective pillars) in 2011 amounted to 84.98 billion tonnes, decreasing by 356 million tonnes (0.42 % of domestic resources) in relation to the previous year. Economic resources in place increased by 273.9 million tonnes (mainly due to the new estimation of Kłodawa 1 deposit resources). Anticipated subeconomic resources increased by 21 million tonnes.
In 2010 the Zechstein rock salt prognostic resources amounted to 192.46 billion tonnes (to the depth of 2,000 m), whereas perspective resources were estimated on 2.062 billion tonnes(1). Perspective resources of Miocene formation in three regions (to the depth from 1,000 to 1,500 m) are equal 2.45 billion tonnes and perspective resources of Pogórska Wola region (to the depth of 1,500-2,000 m) are estimated on 44 million tonnes. Total prognostic resources of rock salt in Poland amounted to 194.904 billion tonnes and perspective resources - 2.062 billion tonnes.
Rock salt deposits in Poland are presented on the map.
Table 1 shows resources and the current state of exploration and development of domestic rock salt deposits. Data refer to resources excluding those within protective pillars.
In 2011 about 2,718 thousand tonnes of salt were produced by solution mining method (Góra and Mogilno I and II mines), which accounts for 71.7 % of domestic production. Moreover, 739 thousand tonnes of crushed salt were extracted in the Kłodawa mine (19.5 % less than in the previous year).
The figure given below shows changes in resources and production of rock salt in Poland in the years 1989-2011.
In 2011 the Dębieńsko Desalination Plant Ltd. recovered 86,622 tonnes of evaporated salt with NaCl content of about 98 % from treatment of brines and salty water from Upper Silesian Coal mines. This means a 0.6 % decrease in production in relation to the previous year (87,110 tonnes).
Prepared by: Grzegorz Czapowski
(1) G. Czapowski, K. Bukowski 2011 - "Sól kamienna i sole potasowo-magnezowe" w "Bilans perspektywicznych zasobów kopalin Polski wg stanu na
31 XII 2009 r." pod red. S. Wołkowicz, T. Smakowski, S. Speczik. PIG-PIB Warszawa.