The Alpine Oligocene plutons are spatially and temporally associated with the activity of the Periadriatic Fault System (PFS), an orogen‐parallel, crustal‐scale transpressive mylonitic belt. ...Excellent three‐dimensional exposure, combined with a wealth of structural, seismic, petrological, geochronological, geochemical, and paleomagnetic data collected over the last decades help to constrain the relationships between deformation, ascent, and emplacement of the plutons. Magmas were channeled from the base of the thickened continental crust into the narrow mylonitic belt of the Periadriatic Fault System, which was used as ascent pathway to cover vertical lengths of 20 to 40 km. Therefore the linear alignment of the plutons at the surface is not the expression of a linear source region at depth. Ascent of the melts is controlled by the mylonitic foliation of the PFS, which forms the only steep anisotropy, continuously traversing the entire Alpine crust. In contrast, the flow direction is not influenced by the specific kinematics of the faults. Final emplacement of the plutons occurred by extrusion from the Periadriatic Fault System into the adjacent country rocks. The transition from ascent to final emplacement is favored by partitioning of transpressive deformation.
Natural kyanites with Cr2O3 contents >1 wt% are very rare and known only from high-P environments, for example, eclogite-facies gabbroic cumulates containing Cr-spinel from the Pohorje Massif, ...Eastern Alps, Slovenia. In these rocks, turquoise-colored Cr-rich kyanites are present in two different textural types. A first type has formed as blocky crystals of several hundred micrometers in size around clusters of small drop-like Cr-spinels. This kyanite shows a highly irregular Cr distribution and may contain up to 15.6 wt% Cr2O3, which is one of the highest Cr2O3 contents reported so far. A second type is present as part of reaction coronas around large red-brownish Cr-spinel and forms deep-blue needle-like crystals that rarely exceed 100 µm in size. This kyanite contains up to 8.2 wt% Cr2O3 and is associated with Cr-rich corundum (≤9.1 wt% Cr2O3) and Cr-Al-rich pargasite (≤3.9 wt% Cr2O3). The formation of kyanite around Cr-spinel droplets is interpreted to be the result of increasing P-T conditions during prograde metamorphism where Cr-spinel and plagioclase or quartz react to Cr-kyanite, ±garnet, ±omphacite. In contrast, the formation of kyanite associated with Cr-rich corundum and Cr-rich pargasite within coronas around Cr-spinel occurred in an early stage of the retrogressive evolution of the gabbroic cumulates at eclogite-facies conditions of ∼2.5 GPa and 750-800°C triggered by the influx of H2O-rich fluids. The driving force for developing these coronas was an increase in the chemical potential of silica caused by the infiltrating hydrous fluid phase. P-T estimates using matrix mineral assemblage place the peak metamorphic conditions close to the quartz/coesite transition with temperatures in the range of 750-810°C and pressures of ∼2.9 GPa.
We study the morphology of the major rivers draining the Eastern Alps to test whether the active tectonics of this part of the orogen is reflected in the shape of channel profiles of the river ...network. In our approach we compare channel profiles measured from digital elevation models with numerically modelled channel profiles using a stream power approach. It is shown that regions of high stream power coincide largely with regions of highest topography and largest uplift rates, while the forelands and the Pannonian Basin are characterised by a significantly lower stream power. From stream power modelling we conclude that there is young uplift at the very east of the Eastern Alps, in the Bohemian Massif and in the Pohorje Range. The impact of the Pleistocene glaciations is explored by comparing properties of rivers that drain in proximal and distal positions relative to the ice sheet during the last glacial maximum. Our analysis shows that most knick points, wind gaps and other non-equilibrium features of catchments covered by ice during the last glaciations (Salzach, Enns) can be correlated with glacial processes. In contrast the ice free catchments of the Mur and Drava are characterized by channels in morphological equilibrium at the first approximation and are showing only weak evidence of the strong tectonic activity within these catchments. Finally, the channel profiles of the Adige and the divide between the upper Rhine and Danube catchments differ significantly from the other catchments. We relate this to the fact that the Adige and the Rhine respond to different base levels from the remainder of the Eastern Alps: The Adige may preserve a record from the Messininan base level change and the Rhine is subject to the base level lowering in the Rhine Graben.
Two monazite generations (M1; M2) were distinguished in a kyanite-garnet gneiss from the UHP terrain of the Pohorje Mountains, Slovenia. P-T estimates reveal a peak event at 760°C/2.6 GPa and ...isothermal decompression down to 700°C/0.6 GPa. M1 type provides a Th-U-Pb mean date of 100±6 Ma, ThO2 contents between 3-7 wt%, Y2O3 values <0.3 wt%, and La/Nd ratios (1.2-1.4) that are clearly higher than for the whole-rock La/Nd (1.1). The absence of Y zoning in M1 and the lack of monazite inclusions in garnet indicate that M1 formed after the main stage of garnet growth (>1.2 MPa), probably close to the P-T peak. M2 type is slightly younger than M1 (74±16 Ma), and has a lower La/Nd (0.3-0.9), lower ThO2 (0.1-5 wt%), and higher Y2O3 (up to 3.2 wt%). Most M2 monazites occur as tiny needles within apatite (subtype M2-a) or along apatite margins (M2-b). Parasitic growth of M2-a and -b from apatite is supported by its low ThO2 (<1 wt%) and La/Nd (<0.5). Isolated matrix grains (M2-c) and overgrowths around M1 (M2-d) have slightly higher La/Nd (0.5-0.9) and higher ThO2 (5 wt%) and were supplied from an apatite and M1 source. Elevated yttrium suggests that M2 formed during decompression, when garnet was consumed and Y was released. These observations imply that at UHP conditions MREE-rich apatite coexisted with low-MREE M1 monazite and reacted during decompression to Ca-F-apatite plus MREE-rich M2 monazite. This provides strong arguments that REE-partitioning between apatite and monazite is pressure-dependent.
Kyanite-rich and quartz-rich eclogites occur as lenses within amphibolite-facies quartzo-feldspathic gneisses in the Pohorje Mountains, Northern Slovenia, that form the easternmost Austroalpine ...basement. Major and trace elements indicate that the kyanite-rich eclogites were derived from plagioclase-rich gabbroic cumulates, whereas the quartz-rich eclogites represent more fractionated basaltic compositions. Both varieties are characterized by a LREE-depleted N-MORB type REE signature. Geothermobarometry and
P–
T pseudosections indicate that eclogites equilibrated at 1.8–2.5 GPa and 630–700 °C, consistently with the lack of coesite and with equilibration conditions of the chemically similar eclogites from the adjacent basement units at Koralpe and Saualpe type localities. Decompression reaction textures include (i) clinopyroxene–plagioclase intergrowths after omphacite, (ii) replacement of kyanite by corundum–plagioclase–spinel±sapphirine symplectites, (iii) breakdown of phengite to biotite–plagioclase sapphirine symplectites. The results of this study indicate that Koralpe, Saualpe and Pohorje high-pressure rocks represent former MORB-type oceanic crust that was subducted in the course of the late Cretaceous (approximately 100 Ma ago) collision between the European and the Apulian plates.
The Periadriatic lineament is a 700-km-long, first-order tectonic boundary in the Alps, along which several Tertiary intrusions are located that were emplaced while tectonic processes were active. ...The Pohorje pluton is one of the Periadriatic magmatic suites and comprises a pluton and a dacite stock that were emplaced at depths of about 10 and 2 km, respectively. Oriented samples were collected from 33 sites in the magmatic, and three in the surrounding metamorphic rocks and subjected them to standard palaeomagnetic and magnetic susceptibility anisotropy processing. There is extreme variation in susceptibility (although the magnetic mineral are always magnetite) and in its anisotropy within the pluton. Lowest values are in the mafic members (in the gabbro, the oldest and in some lamprophyres, the youngest member of the plutonic suite), while the tonalite (granodiorite) exhibits extreme variation, far exceeding those observed for other Periadriatic plutons. The ‘abnormality’ of the Pohorje pluton is attributed to the complex history that involves assimilation, fractional crystallization, stratification in the magma chamber, incorporation of wall rocks, variable degree of K-metasomatism and hydrothermal alteration. Despite the above-described heterogenities and sometimes very high degree of susceptibility anisotropy (much higher that in the metamorphic samples) in the acid member, the palaeomagnetic directions observed for the pluton define three clear-cut groups. The directions show no dependence on the degree of magnetic susceptibility anisotropy. In the order of crystallization, they exhibit decreasing degree of clockwise declination deviation from north. The dacite stock is characterized by counter-clockwise rotated declinations. As the Pohorje pluton was uplifted very fast within the right-lateral Periadriatic shear zone system, it is interpreted that the palaeomagnetic directions observed for the pluton are evidence for a clockwise rotation during exhumation. The palaeomagnetic directions for the dacite, which formed after the climax of the external forces, fits the regional pattern of counter-clockwise rotation observed in the Neogene sediments around the Pohorje pluton. This shows that by the time of the dacite intrusion, the Pohorje pluton was already incorporated into the ‘block’ that was driven by counter-clockwise rotated Adriatic microplate.
As a former part of the great Roman Empire, Slovenia has many archaeological sites featuring buildings and objects entirely or partly constructed from marble whose provenance is doubtful. In ...Slovenia, the most probable source of such marble is the Pohorje Mountains. For the purpose of supporting further provenance studies, these marbles are fully scientifically characterized. The techniques used are petrographic and geochemical analysis, stable isotope ratio analysis and EPR spectroscopy. The results show that the Pohorje marbles are highly heterogeneous in both their isotopic and geochemical parameters as well as grain sizes. The parameters of the different Pohorje marble outcrops are compared between themselves and with the parameters of known ancient quarries in the Mediterranean and Austria. The use of a multi‐technique approach with combined parameters allows the best possible discrimination.
Grassland habitats were studied on twenty farms on the area of the Radlje ob Dravi administration unit, in the transect from Kozjak to Pohorje at different altitudes. The aim of the study was to ...investigate how environmental and socio-economic parameters influence the diversity of plant species and, consequently, the conservation of grassland on acid soils, which are rare in Slovenia and are therefore more protected. The socioeconomic structure of farms was studied on the basis of an inquiry carried out on farms. Part-time farms prevail; the average age of farmers is 56.5 years, and 30% of farmers has no education or just elementary school. The relationship among the environmental, socio-economic parameters and floristic structures of grasslands was studied using canonic-correspondence analysis. The impact of 16 parameters was analysed, of which six were determined not to be statistically significant. The occurrence of chosen plant species was analysed in relation to environmental and socioeconomic parameters. The efficiency of agro-environmental subsidies in relation to plant species diversity was evaluated. It was determined that the education and age of farmers influence the intensity of farming and consequently have an impact on the diversity of plants species and the conservation status of grasslands.
PDF
