Mineralizacja Cu-Ag w utworach cechsztynu – zarys historii poszukiwań i badań prowadzonych przez PIG

Sławomir Oszczepalski, Andrzej Chmielewski

Abstrakt


Cu-Ag Zechstein-hosted mineralization – an outline of the history and research by the Polish Geological Institute.
A b s t r a c t. Discovered by J. Wyżykowski in 1957, the Lubin–Sieroszowice deposit is a classic representative of the giant Kupferschiefer-type Cu-Ag stratabound deposit. Its disclosure and documentation was provided by the research work of many geologists of the Polish Geological Institute and many other institutions. During the period of 60 years, the mining and metallurgical industry has been developed to such extent that Poland is now among the world’s major producers of copper and silver. This discovery marked the beginning of the recognition of the deposit and gave rise to further exploration for prospective areas elsewhere in SW Poland. Detailed studies of Rote Fäule alteration have shown that redox boundary is the principal guide to exploration. Later studies of numerous boreholes allowed the researchers to distinguish 38 prospective areas on the reductive side of the redox border and Au-Pt-Pd enrichments in oxidized rocks. The Kupferschiefer-type deposits were long considered classic examples of syngenetic mineralization. However, the close relationship between the occurrence of Cu-Ag orebodies and oxidized altered areas, and ore zones progressively transgressive to bedding relative to the Rote Fäule front indicates
that these deposits were formed as a result of fluid-rock interaction caused by ascending migration of moderately low-temperature basinal chloride brines from the underlying red beds within reasonable periods of diagenesis of the reduced hosts. The hematitization was the result of an influx of oxidizing solutions across the centers of oxidized areas that acted as the innermost parts of the telescoped Rote Fäule/ore systems. The early-to-late diagenetic timing of mineralization is constrained by paleomagnetic age of hematite, K-Ar dating of authigenic illite and Re-Os dating of Cu sulfides. The fluid circulation was due to paleogeothermal activity, compactive expulsion, recirculation and (or) seismic movements, corresponding to intracontinental Permian–Triassic rifting. Due to the depletion of shallow resources, extensive deep exploration drilling is required to verify the resource potential in concession prospects existing around the documented deposits. The long-term challenges related to the substantial copper and silver scarcity problems in the future demand for overcoming geological barriers (considerable depths, high overburden pressure, elevated temperature, gas hazard) require the use of innovative technology, creation of favorable investment conditions and preparation of a long-term raw materials strategy.

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