Rock salt
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 5.1% of domestic resources. However, geological structure of these deposits is very complex due to intense folding (except for Rybnik-Żary-Orzesze deposit which is situated in a tectonic trough). That complexity of geological structure along with a 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 the country area, mainly in the Polish Lowlands. In the Late Permian these areas were occupied by evaporitic epicontinental basin which was the place of salt sediments accumulations 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. Anticipated economic resources of these deposits are estimated at 26.1 billion tonnes, which accounts for 30.6% 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 documented in a number of the shallowest of these structures. Proven anticipated economic resources of deposits related to the salt structures are estimated at almost 54.3 billion tonnes, which accounts for 64.2% of domestic salt resources. Exploitation of the latter deposits gives 100% of the current domestic salt production. Large bedded rock-salt deposits were also explored in the overburden of the copper ore deposits in the Fore-Sudetic Monocline (copper ore deposit Sieroszowice and rock salt deposit Bądzów – documented in 2013 – which is the part of Sieroszowice deposit).
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 (gas), Góra (fuels) and put into operation in 2014 Kosakowo storage with the capacity of 119 million m3 (within Mechelinki deposit). The salt domes are also being used as safe disposal sites for wastes – for example Asse and Morsleben domes and Herfa-Neurode or Heilbronn mines in bedded rock-salt deposits in Germany, or mines located in bedded potassium and rock salt deposits in the area of Regina (southern Saskatchewan) in Canada. In Alberta Province (Canada) the crude oil recovered from bituminous sand is stored, whereas the exploitation wastes are being disposed – stored in caverns within Devonian salt formations: Lotsberg and Prairie.
Anticipated economic resources of rock salt (excluding those within protective pillars) in 2016 amounted to 85.35 billion tonnes, decreasing by 31.6 million tonnes (0.04 % of domestic resources) in relation to the previous year due to the exploitation. Anticipated sub-economic resources remained unchanged. In the last edition of “The balance…” anticipated sub-economic resources have been presented mistakenly lower due to the wrong counting of Wieliczka deposit resources. Data presented in the current edition are correct. Economic resources in place increased by 265 million tonnes (about 15.3% of domestic resources) due to the reclassification of resources (in Mechelinki deposit economic resources in C1 category increased by 296,621.5 thousand tonnes, in Mogilno I deposit resources in C1 and C2 categories grew by 2,103.8 thousand 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 2016 domestic production of rock salt amounted to 4,079 thousand tonnes (increasing by 17.6% in comparison with the previous year), including 3,125 thousand tonnes coming from a solution mining method (Góra and Mogilno I mines – production increased by 15.5% despite the lack of exploitation from Mogilno II deposit and constituting 76.6% of domestic production). Moreover, 440 thousand tonnes of crushed salt were extracted in the Kłodawa mine (10.8% of domestic production, 15.8% more than in 2015) and from Bądzów deposit there was 40 thousand tonnes extracted (0.1% of domestic production, the triple drop in comparison with 2015).
There were also production coming from the Sieroszowice mine during the preparation works within Kazimierzów I area and works carried out while drilling a new SW-IV shaft. There were 158.5 thousand tonnes of rock salt extracted from anticipated economic resources and 89.4 thousand tonnes from anticipated subeconomic resources (total production equal 247.88 thousand tonnes – increased by 57.5% in comparison with 2015).
The production (in the form of brine) from Mechelinki deposit amounted to 474 thousand tonnes (11.6% of domestic production, increased by 85.2%) – the brine was dumped to the Pucka Bay.
In 2016 Przedsiębiorstwo Gospodarki Wodnej i Rekultywacji Spółka Akcyjna (in Polish) – the former name: Dębieńsko Desalination Plant Ltd., recovered 68,031 tonnes of evaporated salt from treatment of brines and salty water from Upper Silesian coal mines. The production decreased in relation to the previous year by 16.5% in comparison with the previous year.
The figure given below shows changes in resources and production of rock salt in Poland in the years 1989-2016.
Prepared by: Grzegorz Czapowski
Table 1. Rock salt - million tonnes