Polish sediment-hosted stratiform copper deposits associated with Zechstein sediments are one of the country’s most valuable natural resources and the basis for its copper industry. The paper presents the history of their research and current exploration. Although documented deposits and their identified resources are described and characterized, much attention is paid to areas located outside of them, including those where geological exploration is currently underway. The gradual depletion of shallow Cu–Ag reserves in the Lubin-Sieroszowice district and elsewhere in the world requires exploration for deeper-seated deposits. To expand resources, time span and scale of copper production in Poland, exploration and definition of new prospects is of great importance. Thirty-five prospective areas with hypothetical and speculative resources have been delineated in SW Poland, including the most prospective areas adjacent to the Cu–Ag Lubin-Sieroszowice deposit. The paper also focuses on those parts of the Fore-Sudetic Monocline where new copper deposits were recently identified. Their resources are described along with the methodology of establishing their boundaries, which differs from recommended Polish threshold parameters not taking into account the depths exceeding 1500 m. Intelligent modern mining and ore processing technologies are considered as a prerequisite for future profitable development of deposits at deeper levels.
The most significant copper reserves in Poland are confined to sediment-hosted stratiform Kupferschiefer-type deposits that occur at the Zechstein/Rotliegendes transition in the Fore-Sudetic Monocline and North-Sudetic Trough. Gradual depletion of shallow reserves results in exploitation of deeper beds. Latest studies of numerous drill hole cores strongly indicate that the Kupferschiefer series in SW Poland (outside the Lubin-Sieroszowice Copper District) contains a very large volume of prognostic, prospective and hypothetical resources. 38 prospects have been delineated (including 6 areas with prognostic resources, 4 with prospective resources, and 28 areas with hypothetical resources). Among the prospective areas, particular attention is paid to the areas adjacent to the existing mines of Lubin-Sieroszowice copper district, with prognostic resources (Białołęka, Grochowice, Kulów, Luboszyce). Also the areas: Nowiny, Żarków and Mirków are interesting due to accessible depths, Sulmierzyce and Janowo areas due to considerable resources and reasonable depth, and Mozów area – because of high Cu-Ag grading mineralized body with credible continuation to south east through Jany and Grochowice prospects, towards the Lubin-Sieroszowice mining district. It can be estimated that approximately 179 million tons Cu and 346 thousand tons Ag concentrated as potential resources in prospects of SW Poland for future mining, which will be possible, when geological and technological barriers (depth, temperature, oil and gas) will meet economic trends in the world market. Expected progress in underground mining at depths exceeding 1500 m (a depth limit for economic categories) will make this approach effective and technically possible. Additional six prospective areas have been delineated in the contact zone between Upper Silesia and Małopolska blocks, where porphyry-type Mo-Cu-W mineralization (locally with skarns) occurs within porphyry/granitoid rocks and Ediacaran, Ordovician, Silurian, Devonian and Carboniferous metasediments and other sedimentary formations. It should be noted, however, that irregular network of examined drill holes tended to simplify the ranges of prospects and to overestimate resource evaluation. Extensive deep exploration drilling is required to verify resource potential of granted and applied exploration licenses in several targets. The long-term challenges require new solutions for mining industry of the future and industrial market within the EU, to enable the reindustrialization of Europe.
We applied geochemical (ICP-MS, WD-XRF, GFAAS, and AMA 254) and mineralogical (EPMA) studies of 137 samples to ore mineralization from Middle-Triassic sediment-hosted Zn-Pb (Mississippi Valley-type MVT) and Lower Zechstein sediment-hosted stratiform (SSC) Cu-Ag (Kupferschiefer-type) deposits in Poland. They contain a number of trace elements which are not recovered during the ore processing. Only Cu, Ag, Pb, Ni, Re, Se, Au, and PGE are extracted from Cu-Ag deposits while Zn and Pb are the only elements produced from Zn-Pb deposits. Zn-Pb deposits contain Cd, Ag, Ga, and Ba in slightly elevated concentrations and have potential to be mineral resources. This applies to a lesser extent to other trace elements (Bi, As, Hf, Tl, Sb, Se, and Re). However, only Cd and Ag show high enrichment factors indicative of potential for recovery. The bulk-rock analyses reveal strong correlations between Zn and Cd and Se, As and Mo, and weaker correlations between Ag and Cd, as well as Ga and Zn. Electron microprobe analyses of sphalerite revealed high concentrations of Cd (≤2.6 wt%) and Ag (≤3300 ppm). Zn-Pb deposits have fairly significant estimated resources of Ga and Sc (>1000 tons) and Cd (>10,000 tons). The Cu-Ag deposits have element signatures characterized by high values of Co, V, Ni, and Mo and much lower of Bi, As, Cd, Hg, Mo, Sb, and Tl. Bulk-rock analyses show strong correlations between Se and V; As and Co; Bi and Re; and weaker correlations between, for example, Cu and Mo; V, Ni, Ag and Mo; and Ni, V, and Co and Ni. The EPMA determinations reveal strong enrichments of Ag in Cu sulfides (geerite ≤ 10.1 wt %, chalcocite ≤ 6.28 wt %, bornite ≤ 3.29 wt %, djurleite ≤ 9080 ppm, yarrowite ≤ 6614 ppm, and digenite ≤ 3545 ppm). Silver minerals and alloys, as well as the native Ag and Au, were recorded in the Cu-Ag ores. Large resources of Co, V, and Ni (>100,000 tons) and Sc and Mo (>10,000 tons) are notable in Cu-Ag deposits. A number of trace elements, classified as critical for the economy of the European Union, including Ga and Ba (to a lesser extent Hf, Nb, and Sc) in Zn-Pb deposits, and Co and V in the Cu-Ag deposits, may eventually be recovered in the future from the studied deposits if proper ore-processing circuits and increasing demand are favorable.
The Polish Geological Institute – NRI has conducted investigations of the Kupferschiefer series since 1957, when the giant sediment-hosted stratiform Cu-Ag ore deposit was discovered in the central part of the Fore-Sudetic Monocline. Until 1991, a number of drilling programs were completed by PGI-NRI and later research has been focusing mainly on cooperation with oil and gas industry and their core material. Over the last few years, thanks to systematic examination of the drill holes located in the north-western extension, many prospective areas have been recognized and delineated. These prospects are located between Lubin-Sieroszowice deposit and the eastern part of the Zielona Góra oxidized field. In the Kożuchów area, the lower part of Zechstein copper-bearing series contain only relict sulphide mineralization accompanied by iron oxides while reduced rocks with metal sulphides occur in the uppermost part of Zechstein Limestone or at the base of Lower Anhydrite. Grochowice area, where reduced facies prevail in copper-bearing series, is characterized by the predomination of rich Cu-Ag mineralization proximaly to oxidized area. The western part of studied area is dominated by Cu-S type sulphides (chalcocite, digenite, covellite) whereas the eastern part is represented by Cu-Fe-S type minerals (bornite, chalcopyrite) with high galena and sphalerite concentrations. The spatial variability of sulphide mineralization with respect to the oxidized rocks indicates that Bytom Odrzański deposit extends in the north-west direction, continuing in the form of a copper belt along the eastern border of the oxidized area. An extensive deep exploration drilling program is implemented to verify the resource potential within predicted copper belt.
As part of the research subject of the Polish Geological Survey, funded by NFOŚiGW, a research project was carried out at PGI-NRI in 2015–2018. Its main task was quantitative and qualitative identification of elements accompanying the main ore and associated elements, including critical ones, and mineralogical identification of their main carriers in metallic ore deposits documented after World War II, representing the main metallogenic formations in Poland. The research focused mainly on drill cores from historical survey boreholes, rarely samples from open-pits and deep mines, representing: Mesozoic Zn-Pb ores, Lower Zechstein Cu-Ag ores, Mesoproterozoic Fe-Ti-V ores, Mo-Cu-W porphyry ores, stratiform Sn ores in the Sudetes, Variscan vein and metasomatic Au-As polymetallic ores, and Cenozoic Ni ores. The PIG-PIB Chemical Laboratory performed analytical work (ICP-MS, WD-XRF, GF-ASS), which allowed quantitative identification of approximately 60 chemical elements. In addition, complementary mineralogical and petrographic studies of the trace element carriers were carried out using a polarizing microscope and an electron microprobe (CAMECA SX-100). Before sampling, metal ore-bearing intervals were examined for the content of chemical elements using a portable spectrometer (Olympus XRF Delta). The results indicate the presence of numerous elements in studied deposits, including those currently regarded as critical for the European Union economy. The collected materials allowed both developing detailed geochemical and mineralogical characteristics of ores from individual deposits and identifying critical elements. They show a clear correlation with the main ore metals, and their resources can be a matter of interest in terms of raw materials.
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