Abstract: The Horváthertelend Unit, NW foreland of the Mecsek Mountains (Hungary), is known as a pre-Alpine nappe remnant. In this study petrographic examination of the archive thin section collection from the borehole Horvát herte - lend–1 was carried out. The goal of this research is to characterize the mineralogical, petrographic and microstructural features of the black or dark grey fine-grained metasedimentary rocks in the depth interval of 720–790 m. This core section of the borehole Horváthertelend–1 was previously correlated with the Silurian Szalatnak Slate Formation.
The main lithology is the dark metasandstone–slate with quartz (~70%), volcanic rock fragments with intermediate composition (~20%) and detrital plagioclase (~10%) grains. The sandstone is classified as a quartz-rich greywacke with large amount of matrix (~30–40%). In this lithology there are red arkose lenses composed of clay mineral pseudomorphs after detrital feldspar grains (~60%), detrital quartz (~20%) and opacitic biotite (~15%) grains. Idiomorphic, colourless– bluish green, pleochroic epigenic tourmaline with a size of 40–100 μm in the dark rock type and vein-filling prehnite suggests the effect of hydrothermal fluids.
The sigmoidal shape of the lenses and the weakly or moderately developed pressure solution cleavage and the folding of the sedimentary bedding suggest tectonic deformation of the rock body.
Keywords: Horváthertelend, Szalatnak Slate Formation, greywacke, arkose, tourmaline
Abstract: Amphiboles are the main rock-forming minerals in the ultramafic cumulates of the Ditrău Alkaline Massif, Eastern Carpathians, where they appear both as cumulus and intercumulus phases. In olivine-pyroxene hornblendite amphibole represents an intercumulus phase, in plagioclase-bearing pyroxene hornblendite it is both intercumulus and cumulus phases, while in plagioclase-bearing hornblendite it becomes a cumulus phase.
We used the composition of amphiboles to estimate the pressure and temperature conditions of their crystallization. The best results were given by the thermobarometer calibrated also for alkaline systems. Cumulus and intercumulus amphiboles of the Ditrău ultramafic cumulates are supposed to have crystallized at mid to lower crust levels in ~25 km depth indicated by the calculated crystallization temperature and pressure of 900–1050 °C and 6±1 kbar, and 950– 1050 °C and 7±1 kbar, respectively, from a magma containing 6–7% H2O. Based on their composition, the amphiboles are inferred to have crystallized from a Si-undersaturated, differentiated basaltic-basanitic melt. Intercumulus amphi - boles and the enclosed olivine and clinopyroxene cumulus crystals of the Ditrău ultramafic cumulates crystallized from a more primitive melt (mg#amp=0.46–0.48; mg#ol=0.43–0.46; mg#cpx=0.42–0.58), while cumulus amphibole phases were formed from a more fractionated melt (mg#=0.24–0.33).
Keywords: amphibole, thermobarometry, ultramafic cumulate rock, hornblendite, Ditrău Alkaline Massif
Abstract: Middle Triassic basinal carbonates and volcanites (“Buchenstein Group”) representing the oldest formations encountered in the Mesozoic basement of the Zsámbék Basin has been recently exposed in a quarry at the Strázsa Hill near Zsámbék. This succession is overlain by Ladinian to Lower Carnian platform dolomite (Budaörs Dolomite) and a Carnian basinal sequence (Csákberény Formation) exposed in the core Zsámbék Zs–14. The upper part of the Triassic succession is made up by carbonate platform facies of the Upper Carnian – Norian Fődolomit (Main Dolomite) For - mation and the Norian Dachstein Limestone.
The structure of the Mesozoic basement of the Zsámbék Basin is mostly determined by the Vértessomló–Nagy - kovácsi Line of W–E strike. This significant structural zone that is covered by Neogene sediments in the basin is exposed in the quarry of the Strázsa Hill. Along this zone the Norian Fődolomit Formation is in contact with the Middle Triassic volcanites and basinal carbonate succession. The re-evaluation of core Epöl Ep–5 led to the conclusion that the dolomite succession below the lower part of the Dachstein Limestone (Fenyőfő Member) is not the Fődolomite Formation as it was supposed earlier, but the Pelsonian Tagyon Formation and there is a tectonic contact between them. The stratigraphic data and the generally steep dipping of the Triassic formations (40–60°) suggest that the extreme widths of the Middle – Upper Triassic dolomite belt comprising the pre-Cenozoic basement of the Zsámbék Basin is probably the consequence of tectonic repetitions of the successions.
Keywords: Triassic, stratigraphy, tectonics, Zsámbék Basin, Transdanubian Range
Abstract: The goal of the present work is to demonstrate the relationship between the structural development and the depositional environment of the Gajavölgy Member of the Zirc Limestone Fm, and the Villóhegy, and Nána Beds of the Pénzeskút Marl Fm. On the basis of drill-core and quarry descriptions I plotted the thickness maps of the Gajavölgy Member and the Villóhegy and Nána Beds. I also mapped two local hiatuses, bordering the base and the top of the Gajavölgy Member. Based on these results, I found a few evidence for the syn-sedimentary (N)NW–(S)SE compression, which is coincident with the structural data of KISS (2009).
The Gajavölgy Member, which was formed in toe-of-slope environment, has a basin-ward (NNW) decreasing thickness. This direction could be the trend of the progradation as well. Therefore the hiatus at the base of the member can be considered as a downlap surface. The resedimented Triassic extraclasts of the Gajavölgy Member derive form the southern limb of the Transdanubian syncline. These fact show the uplift of the southern limb of the Transdanubian syncline, caused by reactivation of the Early Cretaceous thrusts (e.g. Litér thrust).
During the next transgression, the hemipelagic Pénzeskút Marl was deposited. A gap between the Zirc and Pénzeskút Fm was developed in the NNW part of the basin. This hiatus is located along the deep part of the basin, where continuous transition between the two formations is expected. Therefore the NNW part of the basin, where the hiatus is located, could have been uplifted. I suggest a working model, in which I explain this uplift by the activation of a supposed thrust ramp, whose upper detachment is in the underlying Tés Clay Fm. The related ramp-anticline could be the same, which was mapped on the Hajag Hill by GYALOG & CSÁSZÁR (1982).
The maximal thicknesses of the Villóhegy and Nána Beds are measured in the axis of the basin. These basin-fill sediments reached the maximal thicknesses in a supposed syncline, located between two ramp-anticlines. In this scenario, the Litér thrust would have been reactivated again.
Abstract: Different floodplain levels developed along the Lower Tisza River, in connection with incisions since the Late Pleistocene. The present study aimed to classify the palaeo-channels based on their morphometry, to determine their bankfull discharge, to measure their OSL age, and to identify the floodplain levels based on their height. From the collected data-set we aimed to reconstruct the Late Pleistocene and Holocene development of the Lower Tisza Region.
Three phases of floodplain formation and two phases of incision were defined. However, significant time-span was found between the southern and northern parts of the region. The highest (C) morphological level was active from the beginning of the Late Pleniglacial (25.6±1.4 ka) in the southern part of the study area, thought in the middle and northern part of the study area the C-level was formed later (20.1±2.4–13.2±0.9 ka). At this time the Tisza had 4-5 times greater bankfull discharge (Qbf=8615 m3/s). The first major incision started in the Ságvár–Lascaux interstadial (16.4±1.3 ka) around the Danube and Tisza confluence, but the incision reached the present-day confluence of the Maros River (ca. 175 km upstream) during the Late Glacial (13.1±1.2 ka). There is no great difference between the size of the paleo-channels on the C and B levels, so the incision was probably induced by tectonic activity. The B floodplain level was short-lived ca. 13 ka ago. During the last, but strongest incision phase (in south: 13.4±0.7 ka; north: 10.8±0.7 ka) the Tisza had smaller discharge (Qmk= 3306 m3/s), however the downstream divergence of the floodplain levels and the avulsions on the active floodplain (Level A) support the importance of the tectonic movements on the floodplain development. On the lowest, active A floodplain level 3,2±1,1–1,1±0,7 ka old meanders remained.
Keywords: floodplain development, incision, palaeo-discharge, OSL dating, Tisza
Abstract: Geochemical surveys in Hungary for a long time aimed to help mineral exploration. It was found that instead of using methods tested elsewhere, it is more effective to develop own methods best matching the specific research objectives. In the preliminary and exploratory research phase the study of the dispersion train, while in case of detailed explorations, the study of the dispersion halos proved to be more effective. The background (so-called baseline values) has been determined since the beginning of the 1990s, both separately and in the frame of Pan-European programs. On the basis of soil-forming sediments, four geochemical regions have been distinguished; the differences and possible causes have been determined, along with the expected values of the most important toxic and nutrient elements. High-density surveys (ore mineral & agrochemical research programs) were used to determine the areal representativity of soil samples. Our current research task is to determine the variability of soil samples for each geochemical region.
Keywords: geochemical exploration, chemical analysis, dispersion halos, mineral exploration, stream sediments, agrogeochemistry, baseline studies, background level, statistic methods