The origin of native selenium microparticles during the oxidation of sideritic mudstones in the Verovice Formation (Outer Western Carpathians)

Microparticles of native selenium were detected in weathered sideritic mudstones of the Veřovice Formation (Aptian) of the Silesian Unit (Outer Western Carpatians, NE part of the Czech Republic). This mineral forms small needle-like crystals with lengths of up to 20 μm, and is confined to fissures in sideritic mudstones covered by goethite or rarely also by hydrated Mn-oxide minerals. The oxidized sideritic mudstones show zonal structure and resemble the initial stage of the formation of the so-called rattle stones. From the superposition of phase diagrams of selenium and Fe-oxyhydroxides, Fe apparently occupies a large field in which Se(0) and FeOOH and/or Fe(OH)3 can co-exist. The reduction of selenites or selenates by pyrite or by any other phase, capable of charge transfer, is likely to have been responsible for the formation of microparticles of native selenium. The crucial factor controlling the origin of these particles is the extremely low solubility of Se(0). The source of Se is not obvious. It can be released in trace concentrations during the weathering of pyrite. Sediments of the Veřovice Formation correspond to the anoxic event OAE1b and accumulation of siderophile elements in similar sediments is very probable. A probable mechanism for the origin of Se microcrystals is gradual crystallization from solution.Web of Science66431030

Potential Unconventional Gas Plays in Mature Basin of the Czech Republic

The presence of unconventional resources has been proven in deeper parts of mature oil and gas provinces and coal basins of the world. In this context, it is worth to focus also on the prospects of unconventional gas production from within hydrocarbon provinces of the Moravian part of the Vienna basin. The estimation of hydrocarbon generation potential of Jurasic marls from the Mikulov Formation of the Czech part of the Vienna Basin was performed based on the Rock Eval pyrolysis

The role of mineral phases in the biogas production technology

In the field of electric power industry, renewable energy sources, fertilisers, reclamation, and waste management, biomass is widely studied and used. Minerals are present in every step of biogas transformation, but their forms, occurrence, and composition have not been studied yet. However, there is no comprehensive study research that would address the presence of mineral phases in the process of biogas production. This aim of the study is determination of the amount and composition of the mineral phases present in fermentation residues resulting from different production technologies. Digestate mineral composition was analysed using 46 samples from agricultural biogas plants and university testing biogas reactor. The majority of samples contained the amorphous phase. Minority phases consisted of quartz, albite, orthoclase, muscovite, and amphibole. Opal-CT was found in eleven samples (1.26 to 12.1% wt.). The elements present in gas-liquid fluids or in liquids, gases and aerosols within the biogas technology system may create mineral phases, namely the amorphous phase or the crystalline phase under certain conditions. Opal-CT may enter the fermenter as part of plant tissues referred to as phytoliths, or as an unwanted admixture of different origin. It may also originate from the present amorphous SiO2.Web of Science251595

Hybrid bilayer PLA/chitosan nanofibrous scaffolds doped with ZnO, Fe3O4, and Au nanoparticles with bioactive properties for skin tissue engineering

Burns affect almost half a million of Americans annually. In the case of full-thickness skin injuries, treatment requires a transplant. The development of bioactive materials that promote damaged tissue regeneration constitutes a great alternative to autografts. For this reason, special attention is focused on three-dimensional scaffolds that are non-toxic to skin cells and can mimic the extracellular matrix, which is mainly composed of nanofibrous proteins. Electrospinning, which enables the preparation of nanofibers, is a powerful tool in the field of biomaterials. In this work, novel hybrid poly (lactic acid)/chitosan biomaterials functionalized with three types of nanoparticles (NPs) were successfully developed. ZnO, Fe3O4, and Au NPs were investigated over their morphology by TEM method. The top layer was obtained from PLA nanofibers, while the bottom layer was prepared from acylated chitosan. The layers were studied over their morphology by the SEM method and their chemical structure by FT-IR. To verify their potential in burn wound treatment, the scaffolds' susceptibility to biodegradation as well as moisture permeability were calculated. Also, biomaterials conductivity was determined in terms of electrostimulation. Finally, cytotoxicity tests were carried out by XTT assay and morphology analysis using both fibroblasts cell line and primary cells. The hybrid nanofibrous scaffolds displayed a great potential in tissue engineering.Web of Science121art. no. 15

Manganese-rich carbonate and phosphate concretions from the Subsilesian Unit of the Outer Western Carpathians (Czech Republic): Composition and unique selenium weathering products

This research focuses on two new occurrences of sedimentary concretions in the Subsilesian Unit of the Outer Western Carpathians (Czech Republic) from non-calcareous clays and claystones of the Paleocene to the Eocene age. Powder X-ray diffraction study proved heterogenous matrix, varying in content of siderite, Mn-rich siderite, Ca-rich rhodochrosite and fluorapatite. Electron microscopy revealed microsparitic carbonates with indistinct zoning. According to the geochemical and stable isotope clues the concretions originated in medium to highly reducting environment during early diagenesis. Stable isotope delta C-13 values (-11.3 and -4.8 parts per thousand PDB) and delta O-18 (1.8 and 1.0 parts per thousand PDB) correspond well to early diagenetic marine carbonates and part of the CO2 was derived from oxidation of biological material. Weathering of concretions has been on the surface and along fissures. While siderite-rich concretions produce goethite, rhodochmsite-rich concretions produce a cellular structure of todorokite, birnessite and buserite on rims of carbonate cores. Fissure mineralisation contains association of goethite accompanied by native selenium and clausthalite. The origin of the selenium minerals is interpreted as products on the redox barrier between Me2+/Mn4+ and/or Fe2+/Fe3+, where selenites and selenates are highly soluble but native selenium and selenides are extremely insoluble.Web of Science72216915

Silver mining in Zubří near Rožnov pod Radhoštěm in the light of legends, historical sources and new geological research

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.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

Genetic aspects of barite mineralization related to rocks of the teschenite association in the Silesian Unit, Outer Western Carpathians, Czech Republic

Barite is a relatively uncommon phase in vein and amygdule mineralizations hosted by igneous rocks of the teschenite association in the Silesian Unit (Western Carpathians). In macroscopically observable sizes, it has been reported from 10 sites situated only in the Czech part of the Silesian Unit. Microscopic barite produced by the hydrothermal alteration of rock matrix and also by the supergene processes is more abundant. We examined four samples of barite by mineralogical and geochemical methods. Electron microprobe analyses proved pure barites with up to 0.038 apfu Sr and without remarkable internal zonation. Fluid inclusion and sulphur isotope data suggests that multiple sources of fluid components have been involved during barite crystallization. Barite contains primary and secondary aqueous all-liquid (L) or less frequent two-phase (L+V) aqueous fluid inclusions with variable salinity (0.4-2.9 wt. % NaCl eq.) and homogenization temperatures between 77 and 152 °C. The higher-salinity fluid endmember was probably Cretaceous seawater and the lower-salinity one was probably diagenetic water derived from surrounding flysch sediments during compaction and thermal alteration of clay minerals. The δ34S values of barite samples range between -1.0 ‰ and +16.4 ‰ CDT suggesting participation of two sources of sulphate, one with a near-zero δ34S values probably derived from wall rocks and another with high δ34S values being most probably sulphate from the Cretaceous seawater. All results underline the role of externally derived fluids during post-magmatic alteration of bodies of rock of the teschenite association.Web of Science68212911

High specific activity of radium isotopes in baryte from the Czech part of the Upper Silesian Basin- An example of spontaneous mine water treatment

Radium-bearing barytes (radiobarytes) have been known since the beginning of the 20th century. They are mainly found as precipitates of low-temperature hydrothermal solutions. In anthropogenic environments, they frequently occur as crusts on oil industry equipment used for borehole extraction, in leachates from uranium mill tailings, and as a by-product of phosphoric acid manufacturing. Recently, we recognized Ra-rich baryte as a precipitate in the water drainage system of a bituminous coal mine in the Czech part of the Upper Silesian Basin. The precipitate is a relatively pure baryte, with the empirical formula (Ba0.934Sr0.058Ca0.051Mg0.003)(Sigma 1.046)S0.985O4.000. The mean specific activity of Ra-226 was investigated by the two-sample method and it equals 39.62(22) Bq/g, a level that exceeds known natural occurrences. The values for Ra-228 and Ra-224 are 23.39(26) Bq/g and 11.03(25) Bq/g. The radium content in the baryte is 1.071 ng/g. It is clear that the Ra-rich baryte results from the mixing of two different mine waters-brines rich in Ba, Sr, and isotopes Ra-226 and Ra-228 and waters that are affected by sulfide weathering in mine works. When this mixing occurs in surface watercourses, it could present a serious problem due to the half-life of Ra-226, which is 1600 years. If such mixing spontaneously happens in a mine, then the environmental risks will be much lower and will be, to a great, extent eliminated after the closure of the mine.Web of Science102art. no. 10

FOSFORITOVÉ KONKRECE VE SVRCHNÍ KŘÍDĚ SLEZSKÉ JEDNOTKY

In the stream, Bystrý potok, in the vicinity of Trojanovice by Frenštát p. R., a unique section in flysch deposits of the higher part of the Silesian Unit is outcropped. Phosphorite concretions were found in the glauconitic sandstone in the uppermost part of the section documented in detail. Outcrop represented lower part of the Godula Formation of the Lower Coniacian age. Main components of the concretions are fluorapatite (67%), rodochrosite and quartz

MINERALOGIE KŘÍDOVÝCH ALEUROPELITŮ Z PROFILU BYSTRÝ POTOK (SLEZSKÁ JEDNOTKA, VNĚJŠÍ ZÁPADNÍ KARPATY)

Mineral phases of the pelitic sediments in the Bystrý potok section were identified by RTG difraction. Only small variations in the quantitative representation of individual phases have been distinguished. Main components are muskovite and quartz. Ankerite is present only in samples of Lower Cretaceous of the Hradiště Formation and Lhoty Formation, while hematite is present in samples from red colored pelites of Mazák Formation. Using the oriented and ethylene glycolated aggregates mounts provided presence of clay minerals – smectite, mica (illite), chlorite, kaolinite