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. The deposits occurring in that area are related mainly to the carbonate rock formations of the Silesian-Cracow region built of the 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. In this area, in 2019 there was a new Zn-Pb sulfide ores deposit documented – Laski 1 (the deposit was documentation was the result of Laski, Pomorzany and Bolesław deposits division). The 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. The location of Zn-Pb ores deposits in Poland are presented on the general and detailed maps.
The 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 2019 the copper processing was accompanied by a recovery of 28.51 thousand tonnes of lead.
The most important prospects for the Zn-Pb ores resources growths are connected with the Silesian-Cracow region – where in the carbonate rocks of the Middle Triassic and the Devonian age the sulfide Zn-Pb mineralization od the MVT type occur. As of the 31.12.2018, in the Olkusz region, the estimated prognostic resources are equal about 35 million tonnes of the Zn-Pb ores, whereas in the Zawiercie region – about 25 million tonnes of the Zn-Pb ores*. The Zn oxide ores (the calamines), occurring in the Silesian-Cracow region have not been exploited for many years and their prognostic resources in the abandoned deposits have to be verified and assessed according to the current limit values of the parameters that define the deposit and its borders.
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 (the calamines) 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.
The anticipated economic resources of Zn-Pb ores as of 31.12.2019 amounted to 92.15 million tonnes of ore yielding 3.90 million tonnes of zinc and 1.46 million tonnes of lead. The resources increased by 8.19 million tonnes of ore (that is by 9.75%), 0.31 million tonnes of zinc (8.64%) and 0.05 million tonnes of lead (3.55%). It was mainly the result of the new deposit Laski 1 (+10.77 million tonnes of ore) and the better exploration of Zawiercie 3 deposit – described in the new geological documentation with recalculated resources (+2.94 million tonnes). Due to the documentation of Laski 1 deposit, there was the new documentation with recalculated resources elaborated – the resources decreased by 6.45 million tonnes. The new documentations with recalculated resources were also elaborated for Pomorzany and Klucze I. The anticipated economic resources changes were also the result of the exploitation and losses. Moreover, in 2019 there was also the new documentation with recalculated resources prepared for Bolesław deposit, in which the anticipated sub-economic resources decreased by 0.33 million tonnes – the part of the deposit was included into Laski 1 deposit.
The majority of the anticipated economic resources of Zn-Pb ores is documented in C2 category (52.02%) and C1 category (25.41%), less resources in A+B category (14.72%) and in D category (7.85%).
The anticipated economic resources in exploited deposits account for 16.28% of the total sulfide ore resources. The economic resources of exploited deposits amounted to 3.76 million tonnes of ore containing 0.15 million tonnes of zinc and 0.07 million tonnes of lead. The resources decreased by 0.65 million tonnes (14.74%) in comparison with 2018 due to the exploitation and losses. In 2019, there was a new mining development plan (the supplement no 2) for Klucze I elaborated as a result of the exploitation concession change.
In 2019, Polish mines extracted 1,510 thousand tonnes of ores yielding 40 thousand tonnes of zinc and 20 thousand tonnes of lead. The exploitation of ore decreased by 84 thousand tonnes (5.27%), whereas the output of zinc dropped by 3 thousand tonnes (6.98%) and that of lead increased by 7 thousand tonnes (53.85%).
The figure given below shows changes in resources and production of zinc and lead ores in Poland in the years 1989-2019.
The figure below shows changes in resources and output of zinc in Poland in the years 1989-2019.
The figure below shows changes in resources and output of lead in Poland in the years 1989-2019.
Prepared by: Agnieszka Malon, Stanisław Z. Mikulski, Sławomir Oszczepalski, Marcin Tymiński
* Mikulski S.Z., Retman W., 2020 - Rudy cynku i ołowiu (zinc and lead ores). In: Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31.12.2018 r. (eds. Szamałek K., Szuflicki M., Mizerski W.): 152-161. PIG-PIB, Warszawa.