Zinc and lead ores
Zinc and lead deposits of an economic value occur in the area of the northern and north-eastern margin of the Upper Silesian Coal Basin in southern Poland. Deposits occurring in that area are related mainly to the carbonate rock formations of the Silesian-Cracow region built of Permo-Mesozoic successions resting monoclinally on the Paleozoic sedimentary deposits. Along the regional tectonical Cracow-Libliniec zone these Paleozoic deposits are riddled by the acidic and alcalic igneous-volcanic depoists of the Carboniferous-Permian age. The rock hosting Zn-Pb mineralization ranges in age from the Devonian to Jurassic. Resources of an economic importance are mainly related to the ore accumulations in the so-called ore-bearing dolomites of the Muschelkalk (Middle Triassic). The zinc-lead ores occur in the form of pseudo-layers, sub-horizontal 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 deposits (MVT).
Four areas of Zn-Pb ore deposits are recognized in the Silesian-Cracow region: Chrzanów, Olkusz, Bytom and Zawiercie regions. The exploitation is currently carried out from Klucze I, Olkusz and Pomorzany deposits in the Olkusz region. Zn-Pb deposits of the Bytom and Chrzanów regions are of the historical and scientific importance only. The deposits have been exhausted in the result of the exploitation conducted since the Middle Ages and now comprise some anticipated sub-economic accumulations of mainly oxide ores with minor participation of sulfide ores. The exploitation of deposits of the fourth region (Zawiercie) has not started up to now. In 2018, there were not any works carried out within concession areas. The 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. The average lead contents are only in the range of 0.05-0.3%, therefore the lead recovery is possible only in the course of a copper concentrate treatment in smelters. According to the data provided by the KGHM Polish Copper S.A., in 2018 the copper processing was accompanied by a recovery of 27.21 thousand tonnes of lead.
The best prospective of sulfide Zn-Pb ore resources growth can be expected in the Silesian-Cracow region. Prognostic resources in the Olkusz region amount to 50 million tonnes and in the 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.
Estimations of Zn-Pb ores resources in the Silesian-Cracow region have been changing markedly during the last 50 years. These changes resulted on one hand from an intense exploration and exploitation of the deposits and on the other – from a 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 a technology used at that time in the oxide ore processing. The problems in the technology were finally solved. Therefore, it appeared necessary to introduce special criteria for the classification of 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 31.12.2018 amounted to 83.96 million tonnes of ore yielding 3.59 million tonnes of zinc and 1.41 million tonnes of lead. The resources decreased by 0.46 million tonnes of ore, 0.04 million tonnes of zinc and 0.02 million tonnes of lead. It was the result of the exploitation and losses. The majority of resources have been documented in a C2 category (51.53%) and a C1 category (25.77%), much less in A+B categories (14.86%), whereas only 7.84% in a D category.
Anticipated economic resources in exploited deposits account for 16.77% of the total sulfide ore resources. Economic resources of exploited deposits amounted to 4.41 million tonnes of ore containing 0.20 million tonnes of zinc and 0.07 million tonnes of lead. The resources decreased by 0.55 million tonnes in comparison with 2017.
In 2018, Polish mines extracted 1,594 thousand tonnes of ores yielding 43 thousand tonnes of zinc and 13 thousand tonnes of lead. The exploitation of ore decreased by 117 thousand tonnes (6.84%), whereas the output of zinc dropped by 7 thousand tonnes (14.00%) and that of lead remained at the same level.
The figure given below shows changes in resources and production of zinc and lead ores in Poland in the years 1989-2018.
The figure below shows changes in resources and output of zinc in Poland in the years 1989-2018.
The figure below shows changes in resources and output of lead in Poland in the years 1989-2018.
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.
Table 1. Zinc and lead ores - million tonnes