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Coal-bearing capacity of the Petřkovice Member (Ostrava Formation, Serpukhovian, Mississippian) of the Upper Silesian Basin (Czech Republic and Poland)

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Hýlová L. , Jirásek J. , Sivek M. , Jureczka J.

tom Vol. 60, No. 3

637--649

The Petřkovice Member is the basal unit of the paralic succession of the Ostrava Formation of the Upper Silesian Basin. This member is a valuable source of information about the transition from a marine basin filled with siliciclastic sediments into a paralic basin with the beginning of coal-bearing sedimentation. Models of: (1) the number of coal seams, (2) their total thickness, and (3) the coal content with respect to the total thickness of the succession were created to describe and assess the coal-bearing capacity of the Petřkovice Member. The authors present models for coal seam thicknesses exceeding either 10 or 40 cm. The coal-bearing capacity of the Petřkovice Member is very low. The average share of coal seams thicker than 0.1 m is 3%. The share of coal seams with a thickness that exceeds 0.4 m is only 1.66%. Moreover, in large areas of the basin, in the N and NE parts, the coal-bearing capacity is close to zero, because coal seams of greater thickness were detected only locally there. Based on these models and on other geological data, it is obvious that the onset of coal sedimentation was gradual and limited to particular sites showing the greatest subsidence of the basin floor. In places where minor subsidence took place, there were likely unfavorable conditions for accumulation of organic matter.

Gold deposits of the Czech Republic from a mineral policy perspective

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Janíková P. , Starý J. , Klika R. , Kavina P. , Jirásek J. , Sivek M.

2015

tom T. 31, z. 4

35--49

Gold production in the region that currently makes up the Czech Republic has a thousand-year-old tradition with peaks around the third century BC, 14th century AD and 20th century AD. In general, approximately 100 metric tonnes were produced by the end of mining in 1994, of which nearly 9 tonnes were produced in the 20th century and approximately 3 tonnes were produced after World War II. Significant gold deposits were discovered during the last extensive exploration conducted in the 1970s to 1995, motivated by the sharp rise in the price of gold at the beginning of the 1970s and in the 1980s. Fifteen deposits with 239 tonnes of geological resources of gold were registered. Another 112 tonnesare recorded as prognosticated resources. None of these deposits are mined, due to unresolved issues involving environmental protection. The exploitation of these deposits is restricted primarily due to concerns regarding the environmental impacts of the mining and processing of extracted minerals. A key aspect of these restrictions is likely the existing ban on the use of cyanide mining technologies. A new and yet-to-be-approved proposal for an updated mineral policy in the Czech Republic is attempting to gradually change this stance. Yet another problem lies in the unfinished surveys of mineral deposits, which would specify the total amount of gold and upgrade the resources to higher categories concerning the level of exploration. Without these, it is impossible to prepare the necessary economic assessments of potential production and of the deposits to the fullest extent of activities involving exploration, mineral extraction and processing, including subsequent reclamation of affected areas, elimination of mining impacts and regeneration of post-mining landscapes. The future of gold deposits in the Czech Republic also greatly depends on future trends in the price of gold and accompanying (by-product) minerals occurring together with gold in mined ores.

Produkcja złota w Czechach ma ponad tysiącletnią tradycję sięgającą trzeciego wieku przed naszą erą. Ogółem do końca 1994 roku wyprodukowano około 100 ton złota, z czego prawie 9 ton zostało wyprodukowanych w XX wieku i około 3 tony − po II wojnie światowej. Znaczne złoża złota odkryto podczas ostatnich rozległych badań, przeprowadzonych w latach 1970−1995, które determinowane były gwałtownym wzrostem cen złota w latach 1970−1980. Odkryto 15 złóż złota o zasobach geologicznych wynoszących 239 ton. Kolejnych 112 ton złota oszacowano w zasobach prognostycznych. Żadne z tych złóż nie jest eksploatowane z powodu nierozwiązanych problemów dotyczących ochrony środowiska. Eksploatacja tych złóż jest ograniczana przede wszystkim ze względu na obawy dotyczące wpływu na środowisko procesów wydobywczych i przetwórstwa wydobywanych kopalin. Kluczowym aspektem tych ograniczeń jest istniejący zakaz stosowania technologii wydobywczych z wykorzystaniem cyjanku. Nowy, jeszcze nie zatwierdzony, wniosek o zaktualizowanej polityce surowców mineralnych w Czechach, stopniowo stara się zmienić tę postawę. Jeszcze innym problemem są niedokończone badania złóż kopalin, które określą całkowitą ilość złota i spowodują przeszacowanie zasobów do wyższych kategorii. Bez nich niemożliwe jest przygotowanie niezbędnych analiz ekonomicznych, potencjalnej produkcji, rekultywacji obszarów dotkniętych działalnością górniczą. Przyszłość złóż złota w Republice Czeskiej zależy również od przyszłych trendów cen tego surowca i towarzyszących mu (produkt uboczny) minerałów.

U-Pb zircon age of the Krásné Loučky tuffite : the dating of Visean flysch in the Moravo-Silesian Paleozoic Basin (Rhenohercynian Zone, Czech Republic)

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Jirásek J. , Wlosok J. , Sivek M. , Matýsek D. , Schmitz M. , Sýkorová I. , Vašíèek Z.

Geological Quarterly

2014

tom Vol. 58, No. 4

659–-672

The only previous U-Pb zircon date for the the Early Carboniferous flysch sequence of the Moravo-Silesian Paleozoic Basin was published in 1987 from tuffogenic material from Kobylí Quarry at Krásné Loučky near the town of Krnov (Silesia, Czech Republic). The measured age of 319 Ma did not agree with its stratigraphic position, and was used as the basis for a hypothesized block of Late Carboniferous paralic molasse incorporated during a later tectonic event. During a survey of the still active quarry in 2010, volcaniclastic horizons were identified and sampled. Direct correspondence of the tuff units to those sampled in 1987 cannot be proved but is likely. High precision chemical abrasion - thermal ionization mass spectrometry (CA-TIMS) U-Pb dating of zircon from this new material has yielded an age of 340.05 ± 0.22 Ma, which correlates to the previously inferred stratigraphic age of the locality and the current calibration of the Early Carboniferous geologic time scale. The newly established age corresponds to the Visean stage and dates the boundary between the Horní Benešov and Moravice formations that can be correlated with other foredeep basins of the Culm in the European Variscides. A population of detrital Cambro-Ordovician zircons and a single 2.0 Ga old zircon crystal from the same volcaniclastic layer dated by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) are consistent with the known age of source material in the Variscan orogenic front.