SHALLOW LEVEL LOW-SULPHIDATION TYPE EPITHERMAL SYSTEMS IN THE REGEC CALDERA, CENTRAL TOKAJ MTS., NE-HUNGARY
Abstract: Detailed investigation of the Regec caldera in the Central Tokaj Mts. revealed several types of hydrothermal centers of low-sulphidation type formed at different paleolevels. At the paleosurface, a hydrothermal eruption breccia and layered siliceous deposit of opal-C and -CT material with cinnabar and anomalous enrichments of Hg and Sb were formed from a hot spring. Silicified tuff horizons with alunite-kaolinite alteration indicate steam-heated zones. This type of alteration was formed in the near surface zone, probably above the paleowater table. Stable isotope data for large-sized alunite crystals in brecciated tuff may also indicate a magmatic steam origin. In the deeper zone, around 90–140 m minimal paleodepth, adularia-sericite alteration with quartz veining in andesite formed with anomalous Sb, As and Ba concentrations. Two stages of K-feldspar formation can be recognized: 1. metasomatic K-feldspar, replacing plagioclase phenocrysts, and 2. late adularia in quartz-pyrite-veinlets. Intensive brecciation and adularia formation suggest a pressure drop and boiling of the mineralizing fluids. Late stage quartz crystals show frequent homogenization temperatures between 170 and 190 °C and a maximum salinity of 3 wt. % NaCl equiv. Stable isotope data for quartz crystals suggest that the dominant mineralizing fluid was meteoric water that underwent exchange reaction with the host rock and/or mixed with magmatic water.
CALCAREOUS DINOFLAGELLATE AND CALPIONELLID BIOEVENTS VERSUS SEA-LEVEL FLUCTUATIONS RECORDED IN THE WEST-CARPATHIAN (LATE JURASSIC/EARLY CRETACEOUS) PELAGIC ENVIRONMENTS
Abstract: Recently established separate dinoflagellate cyst zonation combined with the successive calpionellid events contribute to the HIRES of the Upper Jurassic and Lower Cretaceous Tethyan pelagic carbonate sequences. Compositional changes in dinoflagellate and calpionellid assemblages are correlated with eustatic sea-level fluctuations. Thus, parallel calpionellid and cyst zonations give us more precise tools for the subdivision of deposits investigated as well as for better understanding and reconstruction of the paleoceanographical and paleoecological conditions of the ancient marine environments. The calcareous resting cyst distribution is shown to be influenced by the whole complex of environmental factors such as sea-level transgressive/regressive pulses, hydrological regime, nutrient content etc.
PARAFAVREINA COPROLITES FROM THE UPPERMOST TRIASSIC OF THE WESTERN CARPATHIANS
Abstract: The anomuran thalassinid coprolite Parafavreina thoronetensis Brönnimann, Caron & Zaninetti 1972 is described from thin sections of the Norovica Formation (uppermost Triassic) from the Strazovske Vrchy Mountains in central Slovakia. This ichnospecies is one of the most common in the Norian-Rhaetian shallow marine carbonate rocks of the Tethys Realm.
LOWER TRIASSIC QUARTZITES OF THE WESTERN CARPATHIANS: TRANSPORT DIRECTIONS, SOURCE OF CLASTICS
Abstract: The possibility of localizing the source area for the Lower Triassic (Scythian) quartzites and sandstones (Luzna Fm.) was checked. Cross-bedding measurements show the transport from the Carpathian foreland, from the NW and N (the same as in the Eastern Alps). The source area could be in the eastern part of the Bohemian Massif (now subducted under the Carpathians), or in the Armorican Massif, if the supposed large left-lateral shift of the Central Western Carpathians took place. The sedimentary environment can be characterized as fluvial braidplain of ephemeral sandy-pebbly streams with intervals of eolian transport. Rare intercalations of psephitic clasts contain only the most resistent rocks: vein quartz, quartz porphyries (rhyolites) with their pyroclastics, rare intermediary volcanites, postvolcanic products as jaspers and hematitic quartzites, graphitic metaquartzites, radiolarian lydites, silicified wood of Dadoxylon sp., limnosilicites with pollen grains and a single silicite with ostracods. Various tourmalinitic rocks are the most promising for the identification of the provenance area.
PERMIAN LACUSTRINE PHOSPHATIC SANDSTONE IN THE SOUTHERN GEMERIC UNIT, WESTERN CARPATHIANS, SLOVAKIA
Abstract: Lenses of phosphatic sandstone occurring in the Permian sediments of the Stitnik Formation contain intraclasts of microsphorite as well as minute apatite crystals in the matrix. The microsphorite is composed of pelmicritic and microsparitic aggregates of fluorapatite. The sandstone contains up to 18 weight percent P2O5. The phosphatic sandstone originated in an eutrophic lacustrine environment as a result of phosphorus concentration in lake sediment due to the iron redox cycling and the associated microbiological effects. Two contrasted depositional realms are suggested: 1. a shallow, lacustrine low-energy depositional regime in which adsorption and desorption of iron-bound phosphorus between oxygen-deficient bottom water and anoxic sediment led to the formation of microsphorite deposit; 2. a relatively high-energy depositional regime during which river deltas invaded the lacustrine environment and affected phosphorite reworking. Apatite crystals in the matrix are accompanied by Fe-dolomite, uraninite, U-Ti oxides, Ti oxides, framboidal pyrite, chlorites, muscovite and albite. Their formation reflects diagenetic to very low-grade metamorphic redistribution. A hydrothermal association of minerals represents sulphide mineralization occurring in quartz-carbonate veinlets.
