The Rudno nad Hronom-Brehy ore deposit in Slovakia represents an important locality of epithermal precious metal mineralization in the Central Slovak Volcanic Field.The main ore structures in the area are Anna, Goldschram, Filip, Johan de Deo and Priečna veins.In this work, we present mineralogical, paragenetic and geochemical aspects of the ore mineralization, hydrothermal alteration patterns, fluid inclusions, isotopic composition of sulfur (δ 34 S) and K-Ar age of ore mineralization.Four mineralization stages were recognized, the third one being split into two substages.(1) Pyrite stage with quartz, K-feldspar, arsenopyrite and pyrite.(2) Base-metal stage with sphalerite, galena, chalcopyrite, Au-Ag alloys and famatinite.(3a) Early Ag stage with tetrahedrite-(Zn), tetrahedrite-(Fe), argentotetrahedrite-(Zn), tetrahedrite-(Cd), argentotetrahedrite-(Cd) and greenockite.(3b) Late Ag stage with pyrargyrite, polybasite, pearceite, cupropolybasite, cupropearceite, acanthite and galena.(4) Late Ag-Cu stage with bornite, stromeyerite, mckinstryite, chalcocite, digenite, covellite and uytenbogaardtite.Veins are rich in silver with an average Ag : Au ratio of 85 : 1; in some parts of the veins, Ag content reaches up to 1950 ppm and Au up to 42.7 ppm.The neutral to alkaline style of hydrothermal alteration is represented by K-feldspar, quartz, carbonates, smectite, interstratified illite/smectite, and chlorite (clinochlore, chamosite).This assemblage indicates a low sulfidation origin of the mineralization formed at 177-224 °C.The δ 34 S values from the base-metal stage varies from + 2.8 to + 3.5 ‰ for chalcopyrite from the northern part of the Priečna vein, from + 1.9 to + 2.6 ‰ for galena, from + 4.9 to + 5.2 ‰ CDT for pyrite from the Anna vein.These values indicate a relatively homogeneous sulfur source, most likely related to an igneous or mixed igneous and host-rock source.Fluid inclusions in quartz associated with the base-metal stage have low salinity (1.1-1.6 wt.% NaCl eq.) and homogenization temperatures of 176-250 °C.The available data suggest that the base-metal stage was accompanied by cooling and dilution owing to a meteoric fluid.The temperature estimated from the tetrahedrite thermometer of the early Ag stage is ~170-205 °C.According to the paragenetic relationship and mineral stability, the deposition temperatures in the late Ag stage did not exceed 160 °C.The late Ag-Cu stage formed at temperatures of < 93 °C.The results of K-Ar radiometric dating from the hydrothermal alteration returned an average age of 12.5 ± 0.3 Ma.The studied mineralization is possibly related to the initial stage of resurgent horst tectonic activity and rhyolite volcanism of the fifth stage of Štiavnica stratovolcano formation.
Abstract. The study of freshwater carbonates, such as travertines and speleothems, provides valuable insights into the regional biases of mid-Holocene climate development in Central-Eastern (CE) and South-Eastern (SE) Europe. The formation of a lake in the travertine deposition system of the Santovka site, located at the transition of the Western Carpathians and the Pannonian Basin, has led to the preservation of a valuable record. We analyzed the litho- and microstratigraphy, chemical composition, including δ18O and δ13C stable isotopes, and geochronology of the Santovka-village section. We then compared these palaeoclimatic records with reference records from Central-Eastern and South-Eastern Europe in terms of significant climate shifts. The prevalent part of the section studied, which spans between 8200 and 6400 cal BP, is represented by fluvial/fluvio-lacustrine sediments and lake marl. The 8.2 ka BP event was only detected in the δ13C record from the nearby Santovka-PB section. However, we found an abrupt change in both isotopic records around 7400–7200 cal BP, which is likely connected to increased detrital input and some minor palaeoecological changes in the Santovka-village section. These changes are most likely associated with the drying of the lake. The 8.2 event in Central-Eastern (CE) and South-Eastern (SE) Europe is well reflected in the δ13C records, while the change in δ18O was insignificant. In contrast, the newly suggested climate shift around 7400–7000 ka BP was detected at most sites in both δ18O and δ13C records. This development could be connected to a change in air mass circulation, synchronous with declining solar irradiance and increased evidence of drift ice in the North Atlantic.
Abstract We report the first finding of diamond in crustal rocks from the Tromsø Nappe of the North Norwegian Caledonides. Diamond occurs in situ as inclusions in garnet from gneiss at Tønsvika near Tromsø. The rock is composed essentially of garnet, biotite, white mica, quartz and plagioclase, minor constituents include kyanite, zoisite, rutile, tourmaline, amphibole, zircon, apatite and carbonates (magnesite, dolomite, calcite). The microdiamond, identified by micro‐Raman spectroscopy, is cuboidal to octahedral in shape and ranges from 5 to 50 μ m in diameter. The diamond occurs as single grains and as composite diamond + carbonate inclusions. Diamond vibration bands show a downshift from 1 332 to 1 325 cm −1 , the majority of Raman peaks are centred between 1 332 and 1 330 cm −1 and all peaks exhibit a full width at half maximum between 3 and 5 cm −1 . Several spectra show Raman bands typical for disordered and ordered graphite (sp 2 ‐bonded carbon) indicating partial transformation of diamond to graphite. The calculated peak P–T conditions for the diamond‐bearing sample are 3.5 ± 0.5 GPa and 770 ± 50 °C. Metamorphic diamond found in situ in crustal rocks of the Tromsø Nappe thus provides unequivocal evidence for ultrahigh pressure metamorphism in this allochthonous unit of the Scandinavian Caledonides. Deep continental subduction, most probably in the Late Ordovician and shortly before or during the initial collision between Baltica and Laurentia, was required to stabilize the diamond at UHP conditions.
Deeply buried Pannonian (Upper Miocene) siliciclastic deposits show evidence of secondary porosity development via dissolution processes at a late stage of diagenesis. This is demonstrated by detailed petrographic (optical, cathodoluminescence, fluorescence, and scanning electron microscopy) as well as elemental and stable isotope geochemical investigations of lacustrine deposits from the Makó Trough, the deepest depression within the extensional Pannonian back-arc basin. The analyses were carried out on core samples from six wells located in various positions from centre to margins of the trough. The paragenetic sequence of three formations was reconstructed with special emphasis on sandstone beds in a depth interval between ca 2700 and 5500 m. The three formations consist, from bottom to top, of (1) open-water marls of the Endrőd Formation, which is a hydrocarbon source rock with locally derived coarse clastics and (2) a confined and (3) an unconfined turbidite system (respectively, the Szolnok and the Algyő Formation). In the sandstones, detrital grains consist of quartz, feldspar, and mica, as well as sedimentary and metamorphic rock fragments. The quartz content is high in the upper, unconfined turbidite formation (Algyő), whereas feldspars and rock fragments are more widespread in the lower formations (Szolnok and Endrőd). Eogenetic minerals are framboidal pyrite, calcite, and clay minerals. Mesogenetic minerals are ankerite, ferroan calcite, albite, quartz, illite, chlorite, and solid bituminous organic matter. Eogenetic finely crystalline calcite yielded δ13 values from 1.4 to 0.7‰ and δ18 values from –6.0 to –7.4‰, respectively. Mesogenetic ferroan calcite yielded δ13 values from 2.6 to –1.2‰ and δ18 values from –8.3 to –14.0‰, respectively. In the upper part of the turbidite systems, remnants of the migrated organic matter are preserved along pressure dissolution surfaces. All these features indicate that compaction and mineral precipitations resulted in tightly cemented sandstones prior to hydrocarbon migration. Interconnected, secondary, open porosity is associated with pyrite, kaolinite/dickite, and postdates of the late-stage calcite cement. This indicates that dissolution processes took place in the deep burial realm in an extraformational fluid-dominated diagenetic system. The findings of this study add a unique insight to the previously proposed hydrological model of the Pannonian Basin and describe the complex interactions between the basinal deposits and the basement blocks.
Abstract. The study of freshwater carbonates, such as travertines and speleothems, provides valuable insights into the regional biases of mid-Holocene climate development in Central-Eastern (CE) and South-Eastern (SE) Europe. The formation of a lake in the travertine deposition system of the Santovka site, located at the transition of the Western Carpathians and the Pannonian Basin, has led to the preservation of a valuable record. We analyzed the litho- and microstratigraphy, chemical composition, including δ18O and δ13C stable isotopes, and geochronology of the Santovka-village section. We then compared these palaeoclimatic records with reference records from Central-Eastern and South-Eastern Europe in terms of significant climate shifts. The prevalent part of the section studied, which spans between 8200 and 6400 cal BP, is represented by fluvial/fluvio-lacustrine sediments and lake marl. The 8.2 ka BP event was only detected in the δ13C record from the nearby Santovka-PB section. However, we found an abrupt change in both isotopic records around 7400–7200 cal BP, which is likely connected to increased detrital input and some minor palaeoecological changes in the Santovka-village section. These changes are most likely associated with the drying of the lake. The 8.2 event in Central-Eastern (CE) and South-Eastern (SE) Europe is well reflected in the δ13C records, while the change in δ18O was insignificant. In contrast, the newly suggested climate shift around 7400–7000 ka BP was detected at most sites in both δ18O and δ13C records. This development could be connected to a change in air mass circulation, synchronous with declining solar irradiance and increased evidence of drift ice in the North Atlantic.
Newly formed, synkinematically grown minerals in basal cataclasites of the thin-skinned Muráň nappe contain primary fluid inclusions which represent samples of a hydraulic lubricant of the overthrusting nappe block. The inclusion fluid corresponds to a high-salinity brine (37–58 wt% NaCl eq.) of the system Na-K-Ca-Mg-Cl-SO4-CO2. Trapping temperatures between 213 and 471 °C are substantially higher than weak metamorphic imprint of the overlying thrust body. Strongly fluctuating inclusion fluid densities and trapping pressures between 0.2 and 5.4 kbar are interpreted to reflect locally supralithostatic overpressures induced by frictional heating beneath the moving nappe. The results of this study corroborate the hypothesis of Hubert and Rubey [Bull. Geol. Soc. Am. 70 (1959) 115–206], who envisaged a profound effect of pore fluid pressure at the base of moving thrust blocks.
Several caves of hydrothermal origin in crystalline limestones and metasomatic silicites were investigated in the central zone of the Štiavnica stratovolcano, Štiavnické vrchy Mountains, central Slovakia. Evidence of hydrothermal origin includes irregular spherical cave morphology sculptured by ascending thermal water, occurrence of large calcite crystals and hydrothermal alteration of host rocks, including hydrothermal clays. The early phases of speleogenesis in the crystalline limestone near Sklené Teplice Spa were caused by post-magmatic dissolution linked either to the emplacement of subvolcanic granodiorite intrusions during Late Badenian time or to the spatially associated Late Sarmatian epithermal system. Speleogenesis in metasomatic silicites in the Šobov area is related to hydrothermal processes associated with the pre-caldera stage of the Štiavnica stratovolcano in Late Badenian. Both localities are remarkable examples of hydrothermal speleogenesis associated with Miocene volcanic and magmatic activity in the Western Carpathians.
