Facja utleniona cechsztyńskiego łupku miedzionośnego na obszarze monokliny przedsudeckiej

Andrzej Rydzewski



The presence of oxidating facies known are rote Fäule, representing equivalent of Zechstein bituminous copper-bearing shale, was found for the first time in the borehole Dzikowo IG-1 in the area of the Fore-Sudetic Monocline (Lower Silesia), in 1958. The rote Fäule deposits are represented by red-coloured, finely laminated marls and marly limestones with iron oxides. The areas of occurrence of these rocks were studied as they should be eliminated in prospecting for metal ores connected with the contact of the Rotliegendes and Zechstein. The studies took into account borehole data gathered by the Geological Institute, Warsaw, and the Petroleum Prospecting Enterprises from Zielona Góra and Piła. The chemical studies covered about 250 boreholes and the mineralogical-petrographic - abount 500 boreholes.
Six areas of oxidated rote Fäule deposits were discovered in the copper-bearing horizon in the Fore-Sudetic Monocline: (l) Gubin, (2) Nowa Sól, (3) Nowe Miasteczko, (4) Babimost, (5) Lasowice-Ostrzeszów and (6) Niemojewiec, the filrst of which is connected with the large field of that facies in the Zechstein basin comprising Lower Lutetia in the German Democratic Republic. The above mentioned areas of the oxidated shale facies form fields with wavy and fairly diversified contour line. The knowledge of distribution of these areas is very important for prospecting for metal ores in the Lower Zechstein as it was found that the mieralization is increased in reducing facies areas directly adjoning those of the rote Fäule. Copper compounds as a rule occur closer to the boundary between these areas, and lead and zinc compounds - further from this boundary.
The studies carried out in the Fore-Sudetic Monocline showed the predominance of copper on other metals in a belt stretching from Gubin to Kalisz (Fig. 2). Fields with predominance of lead on copper and zinc, and zinc on copper and lead are situated south of the Gubin-Kalisz belt and extend as far as the area of Wrocław, i.e. to the line of present-day extent of the Zechstein.
The studies revealed the action of processes of secondary oxidation of sulfides, which is both characteristic and important for origin of metals in Lower Zechstein rocks, in the areas of the rote Fäule facies (Figs. 4-5). The sulfides evidence subsequent action of ascension type phenomena widening the extent of this facies. The studies on genesis of these processes should be continued in order to explain the problem of two-way formation of oxided deposits and answer whether or nat the formation of deposits of copper-bearing shale horizon in the oxidating facies could result from both the epigenetic processes and the syngenetic sedimentation in marine basin. The inferred relation between distribution of fields of oxidated deposits and the course of Hercynian lineaments rejuvenated by Eocimmerian-Laramic movements makes it necessary to treat these fields as areas influenced by paleohydrogeological phenomena and as migration routes for metallizing solutions.

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