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The Lahóca and Recsk Deep ore complex was formed in relation with andesite volcanics and diorite porphyry intrusives of Paleogene age. The zone is long known for significant enrichment of Cu, Pb and Zn ores. The presence of gold was recorded in the early years of the Lahóca mine. Epithermal and mesothermal gold enrichments are both known in the ore complex. In the epithermal zone low and high sulfidation varieties were identified on the volcanic level of the complex. In the mesothermal zone, significant gold enrichment was indicated in the porphyry copper and skarn copper, zinc ore zones and Pb-Zn veins. In the high sulfidation and the mesothermal copper skarn ore types a moderate correlation between Au and Cu was recorded.

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Abstract

The alkaline basalt of the Füzes-tó scoria cone is the youngest volcanic product of the Bakony-Balaton Highland Volcanic Field. The bombs and massive lava fragments are rich in various crystals, such as mantle-derived xenocrysts (olivine, orthopyroxene, clinopyroxene, spinel), high-pressure mineral phases (clinopyroxene) and phenocrysts (olivine, clinopyroxene). Peridotite xenoliths are also common. Ratios of incompatible trace elements (Zr/Nb and Nb/Y) suggest that the primary magma was formed in the transitional spinel-garnet stability field, at the uppermost part of the asthenosphere. Magmatic spinel inclusions with low-Cr# (22–35) in olivine phenocrysts can reflect a fertile peridotite source. The olivine, orthopyroxene, colourless clinopyroxene and spinel xenocrysts are derived from different depths of the subcontinental lithospheric mantle and their compositions resemble the mineral phases of the ultramafic xenoliths found in this region. The rarer green clinopyroxene cores of clinopyroxene phenocrysts could represent high-pressure products of crystallization from a more evolved melt than the host magma, or they could be derived from mafic lower crustal rocks. Crystallization of the basaltic magma resulted in olivine and clinopyroxene phenocrysts. Their compositions reflect polybaric crystallization with a final, strongly oxidized stage. The Füzes-tó basalt does not represent a certain magma composition, but a mixture of mineral phases having various origin and mantle-derived basaltic melt.

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Central European Geology
Authors: Éva Hartai, Tibor Sasvári, Anna Seres, and László Kuti

Abstract

The Bodrogköz is predominantly a flat area surrounded by the rivers Tisza, Bodrog and Latorica. The Hungarian-Slovakian border cuts it into two parts; consequently, the geologic data in the two countries are different in terms of scale and in approach. The authors harmonized the different data on the two sides and created a unified geologic database for the entire area. The Bodrogköz is part of the depression at the northeastern part of the Great Hungarian Plain. It is covered mostly by Quaternary formations but in the Slovakian part there are smaller outcrops of Permian formations and Miocene volcanics.

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Central European Geology
Authors: Krisztina Buczkó, Enikő K. Magyari, Éva Soróczki-Pintér, Katalin Hubay, Mihály Braun, and Miklós Bálint

Abstract

A high-resolution paleolimnological record from Lake Brazi (TDB-1; 45°23’47″N, 22°54’06″E, 1740 m a.s.l.), a small, glacial lake in the Retezat (South Carpathian Mountains, Romania) provides a sensitive record of the impacts of late glacial climatic change on siliceous algal assemblages. The sequence, ranging from 15,700 cal yr BP to 9500 cal yr BP, suggests that the most significant changes in diatom assemblages took place at 12,800 and 10,400 cal yr BP, when alkaliphilous fragilarioid taxa were replaced by acidophilous diatoms. Altogether eight zones were distinguished with sharp and rapid changes of diatom assemblages. The paper discusses the application of siliceous algae in multi-proxy paleolimnological analyses, demonstrates the advantages and disadvantages of this proxy and presents the story of floristic discovery of unique diatom assemblages, the closest recent analogs of which are found in the arctic region.

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Lake Balaton is a large and shallow lake that is of great economic and cultural importance in landlocked Hungary. Even though the lake has been studied extensively in the last century from a large number of scientific aspects, the mineralogy of its sediments has not been fully explored. The mud at the bottom of the lake consists mostly of silt-sized grains of carbonate minerals with compositions between those of calcite (CaCO3) and dolomite CaMg (CO3)2. In order to understand the processes of carbonate precipitation and the influence of water budget fluctuations on the mineralogical character of the sediment, we used X-ray powder diffraction to analyze the changes of cell parameters of carbonate minerals in the upper half meter of the sediment. The major carbonate phase is Mg-calcite that shows a distinct reduction in cell parameters from west to east, reflecting an increase of its Mg-content, in parallel with a gradient of dissolved Mg/Ca ratio in the water. Intriguingly, dolomite, the other widespread carbonate phase in the sediment, also shows a change in cell parameters from west to east, with the deviations from values of stoichiometric dolomite being largest in the Eastern Basin of the lake. The similar pattern of cell parameter changes of Mg-calcite and dolomite suggests that ordered dolomite with slightly anomalous, Ca-rich composition also forms in the lake, probably by direct precipitation from the water. In contrast, protodolomite forms within the sediment through diagenetic processes. Based on our X-ray powder diffraction measurements, we propose a model of carbonate mineral formation and transformation in Lake Balaton. Since the Mg/Ca ratio of the water appears to be the major factor in controlling the compositions of carbonate minerals, and this ratio in turn is governed by the amount of water supply, the properties of the precipitating carbonate minerals are affected by the actual level of the lake water.

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Central European Geology
Authors: Zsuzsanna Szabó, Nóra Edit Gál, Éva Kun, Teodóra Szőcs, and György Falus

In worst-case leakage scenarios of CO2 geological storage, CO2 or brine may contaminate shallower drinking water aquifers. This work applies an advanced geochemical modeling methodology to predict and understand the effects of the aforementioned contamination scenarios. Several possibilities, such as equilibrium batch, kinetic batch, and 1D kinetic reactive transport simulations, were tested. These have all been implemented in the widely applied PHREEQC code. The production of figures and animations has been automated by R programming. The different modeling levels provide complementary information to each other. Both scenarios (CO2 or brine leakage) indicate the increase of ion concentrations in the freshwater, which might exceed drinking water limit values. The dissolution of CO2 changes the pH and induces mineral dissolution and precipitation in the aquifer and therefore changes in solution composition. Brine replacement of freshwater due to the pressure increase in the geological system induces mineral reactions as well.

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Central European Geology
Authors: János Haas, Tamás Budai, István Dunkl, Éva Farics, Sándor Józsa, Szilvia Kövér, Annette E. Götz, Olga Piros, and Péter Szeitz

The 1,200-m-deep Budaörs-1 borehole provided important data for our understanding of the stratigraphy and tectonic setting of the southern part of the Buda Hills. Although previous reports contained valid observations and interpretations, a number of open questions remained. The importance of this borehole and the unsolved problems motivated us to revisit the archived core. The new studies confirmed the existing stratigraphic assignment for the upper dolomite unit (Budaörs Dolomite Formation) as the dasycladalean alga flora proved its late Anisian to Ladinian age assignment. An andesite dike was intersected within the Budaörs Dolomite. U–Pb age determination performed on zircon crystals revealed a Carnian age (~233 Ma), and settled the long-lasting dispute on the age of this dike, proving the existence of a Carnian volcanic activity in this area after the deposition of the Budaörs Dolomite. Palynostratigraphic studies provided evidence for a late Carnian to early Norian age of the upper part of the lower unit (Mátyáshegy Formation). This result verified an earlier assumption and reinforced the significance of the tectonic contact between the upper unit (Budaörs Formation) and the lower unit (Mátyáshegy Formation). Based on structural observations and construction of cross sections, two alternative models are presented for the structural style and kinematics of the contact zone between the Budaörs and Mátyáshegy Formations. Model A suggests a Cretaceous age for the juxtaposition, along an E–W striking sinistral transpressional fault. In contrast, model B postulates dextral transpression and an Eocene age for the deformation. The latter one is better supported by the scattered dip data; however, both scenarios are considered in this paper as possible models.

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Central European Geology
Authors: Zsófia Pálos, István János Kovács, Dávid Karátson, Tamás Biró, Judit Sándorné Kovács, Éva Bertalan, Anikó Besnyi, György Falus, Tamás Fancsik, Martina Tribus, László Előd Aradi, Csaba Szabó, and Viktor Wesztergom

The past decade has seen a great number of studies dealing with magmatic water contents and how these could be retrieved by the nominally anhydrous minerals’ (NAMs) trace structural hydroxyl (water) contents. Constraints have been made to magmatic hygrometry with clinopyroxene and plagioclase. Although results suggest that the method is more flexible and reliable than melt inclusion studies, they also indicate that the trace hydroxyl contents could still be overprinted by syn- and post-eruptive processes. Clinopyroxenes can hold more structural hydroxyl than plagioclases. A comprehensive review is presented with the inclusion of all published results so far to compile the available pieces of information. As a case study, micro-FTIR measurements are made of a representative set of plagioclase phenocrysts from the Börzsöny Mts. (Carpathian–Pannonian Region). The samples were selected to represent the progress of the volcanic activity in time and space, considering the petrologic and geochemical evolution of volcanic products in well-defined volcanostratigraphic positions. The syn- and post-eruptive cooling rate seems to have the greatest effect on water retention. This means that the systematic investigation of water in volcanic phenocrysts can contribute to distinguish the slowly and rapidly cooling parts of the volcanostratigraphic units.

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Central European Geology
Authors: Máté Zsigmond Leskó, Richárd Zoltán Papp, Ferenc Kristály, József Pálfy, and Norbert Zajzon

other sample was measured after heating to 350 and 550 °C, to observe structural collapse. Identification of crystalline phases was carried out by the Search/Match algorithm in DiffracPlus EVA on the ICDD PDF2 (2005) database. For quantitative mineral

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