The Slovenska Bistrica ultramafic complex (SBUC; Eastern Alps, Slovenia) occupies the south-easternmost part of the Pohorje Mountains, which represent an exhumed piece of continental crust subducted ...during the Cretaceous Eo-Alpine orogeny. The SBUC is composed of serpentinised harzburgites with local occurrences of garnet lherzolite, and is the only known occurrence of ultramafic rocks within the high- to ultrahigh-pressure nappe system apart from a few small dismembered pieces in the near vicinity. The harzburgites are highly depleted following melting within the spinel stability field, as exemplified by high whole-rock MgO contents (41.5–44.3 wt.%), low Al
2O
3 (0.7–1.2 wt.%), low Lu
N (0.1–0.7), and high Cr# of Cr-spinel (ca. 0.5). Fluid-immobile incompatible trace elements (Ti, Sc, V, Zr, HREE, Th) correlate well with MgO, consistent with a melt depletion trend. Other incompatible elements (Ba, Sr, LREE) show little correlation and are probably modified by the serpentinisation process or later metamorphic overprint. However, comparable LREE enrichment of all samples and absence of negative Nb and Th anomalies suggests that this piece of mantle was already metasomatised by melts or fluids before serpentinisation.
Garnet lherzolite in the SBUC recorded an UHP stage (4 GPa, 900 °C) not visible in the harzburgites. Because of the evidence of an earlier lower pressure stage within the spinel stability field, the SBUC represents a piece of subducted mantle. The protolith of the harzburgites is probably oceanic mantle, considering the high degree of melt depletion yet the lack of a subduction-zone signature. It therefore most likely represents a part of previously subducted Meliata oceanic mantle, which was part of a deeper section of the hanging wall along which subduction of the continental crust that is now exposed in Pohorje took place. Alternatively, it may represent mantle depleted and metasomatised in a continental rift zone, which was later incorporated in the hanging wall of the subduction zone and subsequently dragged down to UHP conditions.
Kyanite eclogites from the Pohorje Mountains, Slovenia, are providing the first evidence of ultrahigh-pressureEo-Alpine metamorphism in the Eastern Alps. Polycrystalline quartz inclusions in garnet, ...omphacite and kyaniteare surrounded by radial fractures and exhibit microtextures diagnostic for the recovery after coesite breakdown.The non-stoichiometric supersilicic omphacites found in Pohorje eclogites contain up to 5 mol % of Ca-Eskola molecule.Such clinopyroxenes are known to be stable exclusively at high-pressure conditions exceeding 3 GPa. Theirbreakdown during decompression resulted in exolution of quartz rods and needles that are oriented parallel toomphacite c-axis. The absence of coesite is a consequence of near-isothermal decompression during the first stagesof exhumation.Pressure and temperature conditions for the formation of the peak metamorphic mineral assemblages have beenassessed through a consideration of a) Fe2+-Mg partitioning between garnet and omphacite pairs, based on differentcalibrations; b) the equilibrium between garnet + clinopyroxene + phengite ± kyanite ± quartz/coesite assemblage.Estimated peak pressure and temperature conditions of 3.0-3.1 GPa and 750-783 °C are well within the coesite, i.e.the ultrahigh-pressure stability field.
Ultrahigh-pressure (UHP) metamorphism has been recorded in Eo-Alpine garnet peridotites from the PohorjeMts., Slovenia, belonging to the Eastern Alps. The garnet peridotite bodies are found within ...serpentinized metaultrabasitesin the SE edge of Pohorje and are closely associated with UHP kyanite eclogites. These rocks belongto the Lower Central Austroalpine basement unit of the Eastern Alps, exposed in the proximity of the Periadriaticfault system.Garnet peridotites show signs of a complex four-stage metamorphic history. The protolith stage is represented bya low-P high-T assemblage of olivine + Al-rich orthopyroxene + Al-rich clinopyroxene + Cr-spinel. Due to metamorphism,primary clinopyroxene shows exsolutions of garnet, orthopyroxene, amphibole, Cr-spinel and ilmenite. TheUHP metamorphic stage is defined by the assemblage garnet + olivine + Al-poor orthopyroxene + clinopyroxene +Cr-spinel. Subsequent decompression and final retrogression stage resulted in formation of kelyphitic rims aroundgarnet and crystallization of tremolite, chlorite, serpentine and talc.Pressure and temperature estimates indicate that garnet peridotites reached the peak of metamorphism at 4 GPaand 900 °C, that is well within the UHP stability field. Garnet peridotites in the Pohorje Mountains experiencedUHP metamorphism during the Cretaceous orogeny and thus record the highest-pressure conditions of all Eo-Alpinemetamorphism in the Alps.
The granitic pegmatite dike intruded the Cretaceous UHP rocks at Visole, near Slovenska Bistrica, in the Pohorje Mountains (Slovenia). The rock consists mainly of K-feldspar, albite and quartz, ...subordinate muscovite and biotite, while the accessory minerals include spessartine-almandine, zircon, ferrocolumbite, fluorapatite, monazite- (Ce), uraninite, and magnetite. Compositions of garnet (Sps
Alm
Grs + And
Prp
), metamict zircon with 3.5 to 7.8 wt. % HfO
atom. 100Hf/(Hf + Zr) = 3.3-7.7 and ferrocolumbite atom. Mn/(Mn + Fe) = 0.27-0.43, Ta/(Ta + Nb) = 0.03-0.46 indicate a relatively low to medium degree of magmatic fractionation, characteristic of the muscovite - rare-element class or beryl-columbite subtype of the rare-element class pegmatites. Monazite-(Ce) reveals elevated Th and U contents (≤11 wt. % ThO2, ≤5 wt. % UO2). The monazite-garnet geothermometer shows a possible precipitation temperature of ~495 ± 30 °C at P~4 to 5 kbar. Chemical U-Th-Pb dating of the monazite yielded a Miocene age (17.2 ± 1.8 Ma), whereas uraninite gave a younger (~14 Ma) age. These ages are comtemporaneous with the main crystallization and emplacement of the Pohorje pluton and adjacent volcanic rocks (20 to 15 Ma), providing the first documented evidence of Neogene granitic pegmatites in the Eastern Alps. Consequently, the Visole pegmatite belongs to the youngest rare-element granitic pegmatite populations in Europe, together with the Paleogene pegmatite occurrences along the Periadriatic (Insubric) Fault System in the Alps and in the Rhodope Massif, as well as the Late Miocene to Pliocene pegmatites in the Tuscany magmatic province (mainly on the Island of Elba).
The first evidence for ultrahigh‐pressure (UHP) metamorphism in the Eastern Alps is reported from kyanite eclogites of the Pohorje Mountains in Slovenia. Polycrystalline quartz inclusions surrounded ...by radial fractures in garnet, omphacite, and kyanite are interpreted to be pseudomorphs after coesite. Abundant quartz rods and needles in omphacite indicate an exsolution from a preexisting supersilicic clinopyroxene that contained a Ca‐Eskola component. Geothermobarometry on the mineral assemblage garnet + omphacite + kyanite + phengite + quartz/or coesite yields peak pressure and temperature conditions of 3.0–3.1 GPa and 760°–825°C, well within the stability field of coesite, thus supporting the microtextural evidence for UHP metamorphism. This records the highest‐pressure conditions of Eo‐Alpine metamorphism during the Cretaceous orogeny in the Alps, implying a very deep subduction of the continental crust to at least 90–100 km depths. The new data are evidence for a regional southeastward increase of peak pressures in the Lower Central Austroalpine, indicating a south‐ to eastward dip of the subduction zone. Subduction was intracontinental; northwestern parts of the Austroalpine (Lower Central Austroalpine) were subducted under southeastern parts (Upper Central Austroalpine). The subduction zone formed in the Early Cretaceous in the northwestern foreland of the Meliata suture after Late Jurassic closure of the Meliata Ocean and the resulting collision, by a forward subduction shift to a Permian rift.
The formation and deformation history of back-arc basins play a critical role in understanding the tectonics of plate interactions. Furthermore, opening of extensional back-arc basins during the ...overall convergence between Africa and Europe is a fundamental process in the overall tectonic evolution of the Mediterranean and adjacent areas. In this frame, Miocene tectonic evolution of the western Pannonian Basin of Central Europe and its connection to inherited Cretaceous structures of the Eastern Alpine nappes are presented.
Revision of published and addition of new structural and thermochronological data, as well as seismic profiles from the western Pannonian Basin is complemented by high-resolution thermo-mechanical numerical modeling in order to propose a new physically consistent tectono-sedimentary model for the basin evolution. The onset of extension is dated as ~25–23 Ma, and higher rates are inferred between 19 and 15 Ma at the south-western part of the area (Pohorje, Kozjak Domes, Murska Sobota Ridge, and Mura-Zala Basin). Rift initiation involved the exhumation of the middle part of the Austroalpine nappe pile along low-angle detachment faults and mylonite zones. The Miocene low-angle shear zones could reactivate major Cretaceous thrust boundaries, the exhumation channel of ultra-high-pressure rocks of the Pohorje Dome, or Late Cretaceous extensional structures. Miocene extension was associated with granodiorite and dacite intrusions between 18.64 and 15 Ma. The Pohorje pluton intruded at variable depth from ~4 to 16–18 km and experienced ductile stretching, westward tilting, and asymmetric exhumation of its eastern side. Terrestrial early Miocene (Ottnangian to Karpatian, 19–17.25 Ma) syn-rift depositional environment in supradetachment basins evolved to near-shore and bathyal one by the middle Miocene (Badenian, 15.97–12.8 Ma). Deformation subsequently migrated eastwards to the western part of the Transdanubian Range (Keszthely Hills) and to newly formed grabens. In this formerly emerged terrestrial area active faulting started at 15–14.5 Ma and continued through the late Miocene almost continuously up to ~8 Ma but basically terminated in the Mura-Zala Basin by ~15 Ma (early Badenian). These observations suggest a ~200 km shift of active faulting, basin formation, and related syn-tectonic sedimentation from the SW (Pohorje and Mura-Zala Basin) toward the Pannonian Basin center. Building on the above described observational and modeling data makes the Pannonian Basin an ideal natural laboratory for understanding the coupling between deep Earth and surface processes.
•Variable extensional structures characterize the western Pannonian Basin.•Exhumation of deeper crustal rocks along detachments occurred in the Miocene.•Depocenters and faulting shifted from basin margin toward basin center.•Thermomechanical modelling predicts depocenter migration within 12 Ma.•Miocene extensional structures reactivated and were bounded to inherited weakness zones.
Pseudobrookites (Fe2TiO5-FeTi2O5) are promising candidates for high-temperature oxide thermoelectrics. In this work, we used natural Fe-Ti-rich heavy mineral sand (HMS) as an abundant and ...environmentally friendly raw material for the preparation of pseudobrookite-based ceramics. The main components of the initial powder were ilmenite (FeTiO3) and pseudorutile (Fe2Ti3O9) with various degrees of alteration. Pre-oxidation of the as-received powder was used for modification of the Fe2+:Fe3+ ratio and exsolution of rutile. The starting powders were densified by conventional sintering (CS; 1200 °C, 5 h, pressureless) and spark plasma sintering (SPS; 1100 °C, 5 min, 150 MPs) in argon. The thermoelectric properties of the sintered compacts depend mainly on the Fe:Ti ratio, the Fe2+:Fe3+ ratio, and the fraction and distribution of rutile in the microstructures. The samples exhibit comparable properties as the pseudobrookite-based ceramics prepared from high-purity chemicals indicating that, with some further optimization, natural Fe-Ti-rich HMS are an interesting alternative for the preparation of pseudobrookite-based ceramics for thermoelectric applications.
Coal is one of the main fossil fuel resources and remains the most important contributor to global power generation but coal utilization has severe negative impacts, mostly due to the release of CO2 ...and toxic elements into the environment. This means that determining the quality of coal is important to address the environmental and health problems related to coal combustion. Coal samples from the Velenje coalmine, one of the largest actively mined coal basins in Central Europe, were divided into organic rich and inorganic rich fractions according to the percentage of carbon. Oxides of the major elements (SiO2, Al2O3, Fe2O3 MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3), toxicologically and environmentally relevant elements (As, Ba, Co, Cu, Hg, Mo, Ni, Pb, Th, U, V, Zn, Se) and other trace elements (Ce, Cs, Dy, Er, Eu, Gd, La, Nb, Nd, Pr, Rb, Sm, Sr, Tb, Y, Zr) were measured in sample digests using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of the majority of analyzed elements were either equal to or below the global average for coal. Exceptions were Sr (1090 ± 510 μg g−1, 9 times higher), Ba (301 ± 184 μg g−1, 2 times higher) and Pb (9.12 ± 17.0 μg g−1, 1.4 times higher) in inorganic rich coal and Mo (7.76 ± 4.76 μg g−1, 3.5 times higher) and U (5.24 ± 3.23 μg g−1, 1.8 times higher) in organic rich samples. Eighteen elements (Ag, Au, Be, Bi, Cd, Ga, Hf, Ho, Lu, Sb, Sc, Se, Sn, Ta, Ti, Tm, Yb, W) were below the limit of detection in >70% of the samples. Speciation analysis revealed the presence of several organoarsenic compounds in the organic rich samples, with the tetramethylarsonium ion (TETRA, 0.01–1.10 μg g−1) and trimethylarsine oxide (TMAO, 0.01–0.29 μg g−1) as the most abundant. A comparison with coal samples from the Senovo, Kanižarica, and Trbovlje coal mines in Slovenia and from the Sokolov Basin, (Czech Republic) revealed that Velenje contains much higher amount of organoarsenic compounds (34.8 ± 16.9%) in comparison to the others (4.45 ± 4.19%).
•We investigated element composition in inorganic and organic rich lignite.•Major, minor and trace elements were determined in Velenje lignite.•Values of measured elements are comparable to world coal, except U and Mo.•Unexpected organoarsenic compounds were found in Velenje lignite.•Organoarsenic compounds in Velenje lignite are related to bacterial activity.
In this study the mineralogical and geochemical characteristics of Lake Dojran surficial (0–5, 5–10, 10–15cm) sediments were studied in order to determine their suitability for use as potential raw ...material in balneotherapeutic treatments. X-ray powder diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS) analyses were performed, and thereupon chemical index of alteration (CIA) and enrichment factor (EF) values were calculated.
The XRD results revealed close association of sediment mineralogy with the prevailing metamorphic, volcanic and igneous rocks of the region surrounding Lake Dojran. CIA values of around 67% suggest a moderate degree of weathering in the lake catchment area.
According to the EF value results, surficial Lake Dojran sediments are little enriched with Co, Cr, Cu, Pb, and Zn, moderately enriched with Au, Ni and Sb, moderately severely enriched with Au, severely enriched with Sb and very severely enriched with As. This elemental enrichment likely originates from various different geogenic (geological background and polymetallic mineralization) and anthropogenic (tourism, traffic, coatings, untreated wastewater discharge and agrochemicals) sources. The abundances of the major elements, trace elements and rare earth elements (REEs) were almost constant, changing very little throughout the surficial (0–5, 5–10, 10–15cm) sediments. Comparison of sediment trace element concentrations with consensus-based threshold effect concentration (TEC) and probable effect concentration (PEC) values showed that lake biota may be under threat of contamination with As, Cu and Ni.
Given the present results, we cannot recommend/confirm the application of Lake Dojran dark mud sediment in balneotherapeutic treatments.
•The XRD results revealed close association with the Lake Dojran geology background.•CIA values of 67% suggest a moderate degree of weathering in the lake catchment area.•Sediments are minorly/moderately enriched with Cr, Zn, Pb, Cu, Co, Ni, Au, and Sb.•Elemental enrichment originates from various geogenic and anthropogenic sources.•Use of Lake Dojran sediments for balneotherapeutic treatments cannot be recommended.
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