Zinc and lead ores
The area of northern and north-eastern margin of the Upper Silesian Coal Basin has a long tradition of zinc and lead mining, dating back to the Middle Ages. Deposits occurring in that area are related to carbonate rock formations of the Silesian-Cracow region with Permo-Mesozoic successions resting monoclinally on the Paleozoic basement. Rock hosting Zn-Pb mineralization ranges in age from the Devonian to Jurassic. Resources of economic importance are mainly related to the ore accumulations in the so-called ore-bearing dolomites of the Muschelkalk (Middle Triassic). The ores occur in the form of pseudo-layers, subhorizontal lenses and nest-like replacements. The Silesian-Cracow region is regarded as the world's largest area of Zn-Pb deposits occurrence of the so-called Mississippi Valley type (MVT).
Four areas of Zn-Pb ore deposits are recognized in the Silesian-Cracow region: Chrzanów, Olkusz, Bytom and Zawiercie regions. Klucze I, Olkusz and Pomorzany deposits in the Olkusz region are currently under exploitation. Zn-Pb deposits of the Bytom and Chrzanów regions are of historical and scientific importance only. The deposits have been exhausted in result of exploitation conducted since the Middle Ages and now comprise some subeconomic accumulations of mainly oxide ores. Exploitation of deposits of the fourth region (Zawiercie) have not started up to now. Nowadays, there are exploration and documentation works carried out within concession areas. Location of Zn-Pb ores deposits in Poland are presented on the general and detailed maps.
Zn-Pb concentrations occur also in copper ores of the Zeschstein copper-silver deposits in the Fore-Sudetic Monocline. These concentrations are high enough for lead recovery in the course of copper concentrate treatment in smelters. According to the data provided by the KGHM Polish Copper S.A., in 2015 the copper processing was accompanied by recovery of 29.00 thousand tonnes of lead.
The highest increase of sulfide Zn-Pb ore resources can be expected in the Silesian-Cracow region. Prognostic resources in Olkusz region amounted to 50 million tonnes and in Zawiercie region to 15 million tonnes as of 31.12.2009*. Zinc oxide ore (galmans) prognostic resources are assessed to be equal 60 million tonnes, including 51 million tonnes in abandoned deposits and 9 million tonnes in mining dumps.
Estimates of Zn-Pb ores resources of the Silesian-Cracow region have been markedly changing during the last 50 years. These changes resulted on one hand from intense exploration of the deposits and on the other – from crossing out the resources of zinc oxide ores (galmans) from the official records of domestic resources of mineral raw materials. The decision to cross out the resources was connected with high occupational and environmental hazards associated with technology used at that time in oxide ore processing. The problems in technology were finally solved. Therefore, it appeared necessary to introduce special criteria for classification of Zn oxide ore resources not meeting those of the sulfide ores. Such separate criteria for Zn oxide ore resources were established by the Regulation of the Minister of the Environment on classification for mineral reserves and resources of 9 January 2007. According to the Geological and Mining Law obliging since the 1st of January 2012 there are separated criteria for sulphide and oxide ores deposits called “the limit values of the parameters that defines the deposit and its boundaries”.
Table 1 shows resources and the current state of exploration and development of Zn-Pb deposits.
Anticipated economic resources of Zn-Pb ores as of 31.12.2015 amounted to 83.82 million tonnes of ore yielding 3.57 million tonnes of zinc and 1.42 million tonnes of lead. The resources decreased by 2.20 million tonnes of ore, 0.11 million tonnes of zinc and 0.03 million tonnes of lead. It was due to the new documentations with recalculated resources approved for Klucze and Klucze I deposits and due to the exploitation and losses. The part of the Klucze deposit was subsumed into Klucze I deposit, therefore these two documentations had to be elaborated. There was also the archival documentation with new resources for Jaworzno deposit taking into account in “The balance…”.
Anticipated economic resources within exploited deposits account for 16.6% of total resources. Economic resources amounted to 5.53 million tonnes of ore (containing 0.23 million tonnes of zinc and 0.10 million tonnes of lead). These resources decreased by 1.47 million tonnes.
In 2015, Polish mines extracted 2,241 thousand tonnes of ores yielding 65 thousand tonnes of zinc and 20 thousand tonnes of lead (table 2). The exploitation decreased by 56 thousand tonnes (2.4%).
The figure given below shows changes in resources and production of zinc and lead ores in Poland in the years 1989-2015.
Prepared by: Agnieszka Malon, Stanisław Z. Mikulski, Sławomir Oszczepalski, Marcin Tymiński
*Mikulski S.Z., Strzelska-Smakowska B., Retman W., 2011 - Rudy cynku i ołowiu. In: Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31 XII 2009 r. (ed. S. Wołkowicz, T. Smakowski, S. Speczik): 94-104. PIG-PIB, Warszawa.