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Geologické výzkumy na Moravě a ve Slezsku / Geological research in Moravia and Silesia
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ISSN (Online) 2336-4378
Published by Masaryk University Homepage  [11 journals]
  • Dolování stříbra v Zubří u Rožnova pod Radhoštěm ve světle
           legend, historických pramenů a nových geologických výzkumů

    • Authors: Miroslav Bubík, Dalibor Matýsek
      Abstract: Several historical sources mention silver mining in Zubří village near Rožnov pod Radhoštěm town in the first half of the 16th century. Critical analysis of these sources, new field observations, stratigraphic and mineralogical evaluation of the rocks were carried out to decide whether mining or prospecting for silver can have a real basis. Historical sources from the 18th and 19th centuries are likely to draw uncritically on popular folk tales and reports of fraudulent prospectors. This is evidenced by contradictions in the location of supposed mining, references to fictitious persons and unrealistic descriptions of mine workings. New field observations in Zubří brought improved knowledge of local geology. Clays and claystones from occasional excavations, soundings and outcrops were stratigraphically classified based on foraminiferal micropaleontology. The study area is built of Hauterivian to Paleocene strata of the Silesian Unit of the Carpathian Flysch Belt. At the site marked on the historical map as a former silver mine, no minerals containing Ag and Pb were found. Framboidal pyrite and traces of sphalerite of diagenetic origin were detected using SEM and microprobe method in the sandy limestone intercalation within the Lhoty Formation. The silt from the colluvial clay in the lower part of the site contained dominantly garnets close to almandine, minerals from the TiO2 group and Fe-oxides. Chemical analysis of colluvial clay showed heavy-metal (Ag, Cu, Mo, Zn, Pb) concentrations close to background values. These negative results are consistent with the sceptical conclusions from the analysis of historical sources. The only historical mine observed in the studied area is revealed by an old heap above the road to Staré Zubří. It is undoubtedly related to the mining of pelosiderite. The pelosiderite is abundant in places in the claystones of the Hradiště Formation on Stříbrník and in the Olšovec stream. This source was probably exploited in the first half of the 18th century for the local iron hammer.
      PubDate: 2022-12-22
      DOI: 10.5817/GVMS2022-33040
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Vývoj metamorfních fluid pozdního stádia regionální metamorfózy v
           keprnické klenbě silezika

    • Authors: Tomáš Urban, David Buriánek
      Abstract: Neo-Proterozoic rocks (Brunovistulian Unit) are dominant in the studied area of Silesicum, which have complex nappe, thick-skinned and thrust sheet geological structures. The Keprník Dome (Keprník nappe) represents the easternmost part of crystalline complexes of the Silesian domain and is dominated by various types of orthogneiss, gneiss, mica schist and phyllite, with a small occurrence of calc-silicate rocks. These rocks are affected by pre-Variscan and Variscan metamorphism, dominantly staurolite-sillimanite and garnet zone and late Variscan to Cenozoic brittle deformation. Hydrothermal Variscan quartz veins and surrounding rocks (biotite-bearing paragneiss and orthogneiss) were studied in the Keprník dome geological unit to confront the type of fluids enclosed in fluid inclusions and the intensity of metamorphism that affected the host rocks. The study of fluid inclusions in quartz veins was supplemented by Raman spectrometry and microscopic study of rocks, EMPA and mineral thermometry. Temperatures 616 to 643 °C obtained by the Ti-in-biotite method for biotite paragneisses are compatible with the peak metamorphic conditions estimated by previous authors. Thermometer for orthogneiss provided temperatures between 688 to 699 °C using the Ti-in-biotite thermometer. The lower temperatures (483 to 529 °C) obtained using magnetite-ilmenite thermometer document later retrogression. Three types of fluids were found in the quartz of the Variscan hydrothermal veins based on the phases present, respectively components: I. L+V, H2O–NaCl ± K+ ± Mg2+ ± Ca2+, II. L+V+S±S2, H2O–NaCl–CaCl2 ± K+ ± Mg2+, III. L1+L2+V, H2O–NaCl–CO2 ± CH4 ± K+ ± Mg2+ ± Ca2+ (L – liquid, V – vapour, S – solid). Type II inclusions contain aqueous fluids with high salinities, which would correspond to the post-Variscan systems found (Slobodník et al. 2010a, 2020) in the Silesicum area. On the other hand, they have high Th temperatures, reaching values of over 300 °C. Only results from type I could be used to calculate isochores and derive P-T conditions for the formation of Variscan veins, because in type III often occur fluid inclusion decrepitation and the impossibility of measuring total homogenization. Types I and III according to the structural position of fluid inclusion (uncertain or primary and pseudosecondary inclusions), microthermometric data and composition, they are considered to be metamorphic types of fluids generated by Variscan metamorphism. The evaluation of isochores of the first type of fluids using a lithostatic thermobaric gradient (50 °C/270 bar/km) indicates the entrapment of fluids, or formation of inclusions under conditions of 190–300 °C and 90–160 MPa. This type of fluid was very likely captured at a later stage of metamorphism, after the crystallization of magnetite and ilmenite, and represents a retrograde stage of metamorphism.
      PubDate: 2022-12-20
      DOI: 10.5817/GVMS2022-32965
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Geofyzikální mapování výskytu těšínitové asociace hornin v okolí
           Žermanic – slezská jednotka

    • Authors: Anastasia Melnyk, Lubomil Pospíšil
      Abstract: Picrites, monchiquites, fourchettes, ouachitites, teschenites s.s. and teschenite clinopyroxenites are the representatives of major effusive and hypabyssal rock types of teschenite association rocks (TAR) of the Silesian unit of the Western Carpathians flysch belt. The geophysical image of TAR and their physical properties can be observed mainly in the magnetic and geoelectrical data, mainly from well logs and magnetic maps of different authors. Geophysical research of the TAH was carried out only in a limited scope of works due to unclear and complicated structural-tectonic conditions related to its development in space and time. This contribution provides a detailed overview of the methodology used in the mapping and interpretation of one of the geologically well-explored locality located in the vicinity of the abandoned quarry in Žermanice village. Geophysical works are part of research projects implemented at VŠB-TU in Ostrava. The aim is to verify the possibilities of geophysical methods in monitoring the extent, structural and tectonic position of the TAH. It also includes the creation of GRAV/MAG models based on which the reality of the measured effects caused by the given bodies is verified. At the Žermanice location, geophysical methods were used in the profile variant, namely gravity, magnetic and geoelectrical measurements in the ERT (electrical resistance tomography) variant. The results proved that this combination of methods enable comprehensively map individual TAH bodies and thus appropriately supplement geological and geochemical data and results.
      PubDate: 2022-12-20
      DOI: 10.5817/GVMS2022-21299
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Kompozičně neobvyklé struskové hmoty z polykulturní archeologické
           lokality Boršice v podhůří Chřibů

    • Authors: Zdeněk Dolníček, Ladislav Kandrnál, Jana Ulmanová
      Abstract: We present results of laboratory investigation of slag-like artifacts, found on an archaeological site near Boršice, known by occurrence of artifacts from the Early Neolithic (5 700–5 000 BC), Bronze and Early Medieval Ages. The grey-coloured foamy slag-like artifacts reach up to 5 cm in size and often display original lava-like surface. These slags are formed especially by strongly potassic (15–23 wt. % K2O) silicic (54–72 wt. % SiO2) glass with elevated contents of Ca (4–15 wt. % CaO), P (1–5 wt. % P2O5) and Mg (1–5 wt. % MgO) and only traces of Al, Mn and Fe (below 0.14 wt. % of oxides of each of these elements). Glass phase is partly altered due to weathering, which caused the glass hydration and almost complete loss of K. Sparse minute crystals of wollastonite (CaSiO3) and an unidentified Ca-K-Si-P-O phase (with highly variable compositions and poor stoichiometry) occur in places in the glass phase. We suggest that the origin of the studied slag-like artifacts is probably connected with either modern or ancient production of glass. However, it is certainly not modern foam glass, industrially produced worldwide from used waste glass. Based on average chemical composition of glass, we suggest that the studied artifacts could originate by smelting of a mixture of quartz sand, potash, bone ash, calcitic limestone (or calcitic marble) and dolomite in weight proportions equal to 58.9, 24.6, 4.9, 3.3 and 8.3, respectively.
      PubDate: 2022-12-20
      DOI: 10.5817/GVMS2022-20772
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Sedimenty spodního badenu na lokalitě Zaječí hora

    • Authors: Slavomir Nehyba, Rostislav Brzobohatý, Karel Diviš, Růžena Gregorová, Pavla Tomanová Petrová
      Abstract: Lower Badenian deposits were newly exposed at Zaječí hora Hill (Brno city). Sedimentological and paleontological study of the succession recognised two facies associations. The lower one was formed by the lower Badenian clastic deposits known locally as “Brno sands”. The upper one is formed by the lower Badenian offshore clays known as “tegel”. The Neogene beds were covered by Quaternary loess loam. Lower Badenian succession is interpreted as progradation of the Gilbert-type delta foreset into relatively deep basin followed by the flooding of the area by the open sea. The position of the locality close to a steep basin margin was prone to reflect role of local factors influencing the depositional processes and conditions.
      PubDate: 2022-12-20
      DOI: 10.5817/GVMS2022-20840
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Půdní vývoj v nivě řeky Dyje v předpolí hradby hradiska Pohansko u
           Břeclavi

    • Authors: Katarína Adameková, Jan Petřík, Pavel Dlapa, Michaela Prišťáková, Slavomír Nehyba, Petr Dresler, Andrej Hrabovský
      Abstract: This work provides comprehensive information on soil development on the floodplain of the river Thaya in the area of the foreland of the Early Mediaeval agglomeration of Pohansko near Břeclav. We evaluated the basic properties of late Holocene soils and their genesis, assessed the influence of humans and identified particular soil-forming processes based on a combination of selected physical (grain-size distribution, magnetic susceptibility), chemical (Fe, Mn, P, Ca, soil pH) and biochemical analyses (total organic carbon and soil organic matter) as well as micromorphological observations. Our research revealed three autochthonous soils: two buried soils and one recent soil. All the soils were identified as Gleyic Fluvisols developed from overbank deposits and affected by intensive oxidation-reduction processes. The A horizons of the soils evolved by the formation and accumulation of humus. The upper buried Fluvisol certainly evolved during the 9th and 10th centuries (presence of Great Moravian sherds). However, its pedogenesis possibly started much earlier and ended later. Despite the presence of macroscopic evidence of human activities in this soil, there is no evidence of any anthropic influence on soil formation processes. The basal buried Fluvisol developed even before the Great Moravian settlement. Nevertheless, due to a lack of dating, the exact age of this soil cannot be determined at this stage of our study. Future research focused on dating will advance our understanding of the Holocene dynamic and development of the palaeoenvironment.
      PubDate: 2022-12-20
      DOI: 10.5817/GVMS2022-33071
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Coarse gravel deposits at the Dyje–Pulkau watershed south of Znojmo
           (Czechia–Austria): new knowledge confronted with current stratigraphy

    • Authors: Pavel Roštínský, Jaroslav Šmerda, Eva Nováková
      Abstract: More gravel occurrences are preserved on largely flat summits in the upland area at the Dyje–Pulkau watershed (Carpathian Foredeep nearby distinct southeastern margin of the Bohemian Massif developed along the Waitzendorf fault system) than marked in geological maps. As to stratigraphy, their western sites were hitherto considered to be marine deposits of Lower Badenian (Middle Miocene age). New knowledge about distribution, geomorphological setting, clast size and basic petrography of the gravel compared with some of the same type data on numerous coarse grained Neogene or Quaternary sediments of various genesis preserved in the surroundings (in total 17 basic gravel categories with subhorizontal surfaces distinguished) indicate presumable younger (Late) Miocene or Pliocene age of the deposits, the latter recently proposed for a few eastern gravel sites in Austria. The watershed gravel is distributed in two WNW–ESE trending subparallel belts of different petrology: southern one > 7 km long dominantly composed of quartz-rich rocks (redeposited from sequences of the foredeep basin, mostly Ottnangian) and northern one > 13 km long with high content of Dyje Massif granitoid rocks (lower mineral maturity; primary origin within the margin of the Bohemian Massif, but likely redeposited from younger Lower Badenian sediments) extended across transverse boundary between much finer Karpathian and Lower Badenian sequences in the current Carpathian Foredeep (lower stratigraphic constraint). The analogous petrographic differences also occur between two groups of rare depositional sites within near steep marginal slope of the Bohemian Massif; however, the slope category rich in crystalline clasts includes there double quantity of granitoid rocks and minimum quarzite compared with the northern watershed belt in the foredeep basin. The direction and age of material transport into both watershed gravel belts (from WNW) could be similar to that supplying about 5 other quartz-rich gravel categories in the north or south (supposedly driven by streams from WNW or NW), some containing redeposited moldavites originated about 15 Ma. The presumable (Late) Pliocene onset of the Dyje river downcutting in its present-day deep valley section subparallel to the very outer limit of the Bohemian Massif (higher stratigraphic constraint) could be related to young complex movement activity of the Waitzendorf fault system resulting in current block-type topography and disturbing the older dominant WNW–ESE to NW–SE directed regional transport of clastic material.
      PubDate: 2022-10-26
      DOI: 10.5817/GVMS2022-20639
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Odhad detekční schopnosti stanice VRAC s ohledem na seismické jevy
           registrované v letech 2011 až 2021

    • Authors: Josef Havíř
      Abstract: Širokopásmová seismická stanice VRAC (Vranov u Brna), provozovaná Ústavem fyziky Země (Masarykova univerzita), je zapojena do různých projektů zaměřených na monitorování seismických jevů. Zásadní je zejména její zapojení do globální sítě Mezinárodního monitorovacího systému CTBTO (Comprehensive Nuclear-Test_ban Treaty Organization). Dále je stanice VRAC také jednou z permanentních širokopásmových stanic České regionální seismické sítě. Data stanice VRAC jsou tak rutinně zpracovávána s ohledem na detekci seismických jevů, jejichž zdroje se nachází v různých epicentrálních vzdálenostech, od lokálních, přes regionální až po teleseismické. Cílem tohoto článku je stručně předvést jednoduchý odhad detekční schopnosti stanice VRAC s ohledem na seismické jevy z různých epicentrálních vzdáleností. Tento jednoduchý odhad detekční schopnosti byl založen na studiu magnitudo-četnostních vztahů. K tomuto účelu byl využit soubor seismických jevů registrovaných stanicí VRAC v letech 2011 až 2021. Zmíněný soubor zahrnuje 52246 seismických jevů, z toho 33161 regionálních jevů, jejichž zdroje se nacházely v regionálních vzdálenostech. tj. do 2000 km, od stanice VRAC. V rámci magnitudo-četnostní analýzy byly pro každou dílčí sadu, obsahující vždy jevy z dané epicentrální vzdálenosti, zjišťovány dva parametry, a to: hodnota nejčetnějšího magnituda Ma a hodnota magnituda Mm v minimu derivace funkce závislosti nelogaritmované četnosti jevů na magnitudu. Hodnota Mm dobře odpovídá tomu místu na klasickém magnitudo-četnostním grafu, kde dochází k tzv. roll-off efektu. Grafy obou sledovaných parametrů (Ma i Mm) ukazují strmý nárůst hodnot v regionálních vzdálenostech, následovaný plochou částí křivky v epicentrálních vzdálenostech 20°až 80°. Velmi zřetelně se projevuje snížená detekční schopnost v zónách seismického stínu, a to jak v zóně spjaté se zónou snížených rychlostí v hlubších partiích zemského nitra (vnější jádro), tak i se zóno snížených rychlostí odpovídající astenosféře. Dosažené výsledky umožňují odhadnout detekční práh stanice VRAC pro jevy v epicentrálních vzdálenostech 20° až 80° na hodnotu v rozmezí od 4,5 do 4,9.
      PubDate: 2022-10-26
      DOI: 10.5817/GVMS2022-20824
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Podzemní vody hluboké struktury regionálního rozsahu:
           Pasohlávky–Laa an der Thaya

    • Authors: Kateřina Chroustová, Adam Říčka, Bibiána Pasternáková, Tomáš Kuchovský, Vladimír Opletal, Slavomír Nehyba, Magdalena Bottig
      Abstract: The regions of South Moravia in Czech Republic and Lower Austria are well-known for their use of thermal mineral waters for balneological purposes. Mineral waters are exploited from a Jurassic aquifer by two about 1.5 km deep wells MUS-3G (Pasohlavky, Czech Republic) and Laa TH Nord 1 (Laa an der Thaya, Austria). This Jurassic aquifer buried below the Neogene foredeep overlies a crystalline basement of Bohemian Massif and continues to the southeast below the Western Carpathians. Jurassic sediments which are mainly composed of autochthonous carbonates increase their thickness in this direction due to the decline of the crystalline basement. Because of this decline, there are two developments of Jurassic sediments, the shallower on the northwest and the deeper on the southeast. The zone between these two developments is known as the Mušov transition zone. For sustainable mineral water resources development, a groundwater flow pattern and recharge are evaluated. This evaluation includes both the hydrogeologic structure of Jurassic carbonates and hydraulically continuous underlying and overlying rocks. Because of the considerable depth of this hydrogeologic structure, which ranges from 100 to 3 000 metres below sea level, this study was based mostly on archive reports related to deep wells at the study area. The extent of studied units was identified on well-log data and geophysical survey interpretation. The resulting groundwater level contour map is based on the spatial distribution of hydraulic heads ranging approx. from 180 to 220 metres above sea level (masl) that were derived from pressure and water density conditions at the Jurassic aquifer. The general direction of groundwater flow is from northwest and southeast to the drainage zone (hydraulic head approx. 170–190 masl) identified in the middle of the studied area, which is identical to a course of the Mušov transition zone and parallel to the course of Dyje river (water table 170–180 masl). The northwestern part of the studied hydrogeological structure also differs from the southeastern part in a lower total mineralization which indicates active inflow of fresh water. The study was also enhanced by a spatial distribution of hydraulic parameters of all modelled units. These parameters were derived from hydrodynamic tests. The hydraulic conductivity values for the major Jurassic aquifer range from 6,0×10-4 to 1,3×10-9 m/s. The occurrence of the higher hydraulic conductivity near the drainage zone indicates the presence of a well-developed drainage network.
      PubDate: 2022-10-26
      DOI: 10.5817/GVMS2022-15517
      Issue No: Vol. 29, No. 1-2 (2022)
       
  • Chemické složení amfibolů v polétavém prachu z vybraných lokalit
           Brněnska

    • Authors: David Buriánek, Jiří Svatuška
      Abstract: This study aimed to characterise the morphological and chemical properties of amphiboles from airborne dust in three localities studied in Brno and its surroundings. We analysed approximately 2 g of airborne dust particles from each sample. The mineralogical and morphological characteristics of the dust particles were examined by polarised-light microscopy and electron microprobe analysis (SEM–WDX). All studied airborne dust inorganic particles with length ≥5 μm show ratio ≤3: 1 or diameter ˃3 μm and therefore does not be potentially dangerous to human health. We compared the chemical analyses of airborne dust particles (tremolite-actinolite, magnesiohornblende, pargasite) with existing chemical composition amphiboles from possible source areas. The airborne dust from the locality in the centre of the Brno town is completely dominated by amphiboles derived from basic and ultrabasic rocks of the Central Basic Belt of the Brno Massif. The granitoids of the Brno massif was also a significant source of dust particles. Anthropogenic activity can explain a substantial proportion of amphibole from a relatively small body of amphibolites in the Central Basic Belt of the Brno Massif because these rocks are widely used as sanding material in the entire Brno agglomeration. The second locality of Rosice (west of Brno) is dominated by amphiboles from the west and northwest metamorphic units (Moravian and Moldanubicum). Amphiboles from the rocks of the Brno massif situated to the southeast are also presented. Amphiboles in the airborne dust from the Rajhradice (locality situated SE from Brno) predominantly originated from the rocks of the Central Basic Belt of the Brno Massif (including amphibolites). Calcareous microfossils suggest that an essential component of the dust is also the material transported from the southeast, where dominated sediments of the Carpathian Flysch units and their foreland. Our results validate amphiboles as valuable minerals for identifying source areas from which dust has been derived and confirm dominant wind flows in the SE and NW directions.
      PubDate: 2022-10-26
      DOI: 10.5817/GVMS2022-20874
      Issue No: Vol. 29, No. 1-2 (2022)
       
 
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