Central Western Carpathians Research Articles

Evolution of depositional systems and sedimentary cycles in Želiezovce Depression of the Danube Basin

Five deep wells (Pozba4, Pozba3, Dubnik1, Nova Vieska1, Modrany1), drilled in the Želiezovce depression of the south-east Danube Basin penetrate the Cenozoic sedimentary record in overall thickness ranging from 1000 m up to 3000 m, the total thickness gradually increases from South to the North. This area is well known for the complex geological structure related to the Central Western Carpathians and Transdanubian Range junction along the Hurbanovo – Diosjeno line. Many authors have studied this area in the past, nevertheless Depositional systems, sedimentary cycles and the development of sedimentary facies were never understood in detail. The Re-evaluation of biostratigraphy, paleoecology, sedimentology and the Re-interpretation of e-logs ware all incorporated into well correlations, what resulted in definition of four main sedimentary cycles: (1) The Lowermost Oligocene cycle, consisting of mudstones with occasional sandstone intercalations, associated with slope to offshore marine environment what is supported by the presence of the NP 22 calcareous nannoplankton zone. (2) The transgressive Langhian (Lower Badenian) deposits, composed of mudstones with epiclastic volcanic material and tuffite beds ware associated with shelfall to offshore environement the age is supported by the NN4 - NN5 calcareous nannoplankton zone. (3) The Serravallian (Upper Badenian - Sarmatian) cycle is composed mainly by mudstones with abundant Lithothamnium fragments associated with brackish coastal pain environment, supported by the NN6 calcareous nannoplankton zone and by the mass occurrence of fish scales and Ervilia dissita (Eichwald) bivalves. (4) The overlying strata are represent the Tortonian-Pliocene (Pannonian-Pliocene) cycle, consists mostly from claystone which are overlain by sandstone and siltstones layers is associated with lake, deltaic and alluvial plain environment.

Evolution of Late Cretaceous–Palaeogene synorogenic basins in the Pieniny Klippen Belt and adjacent zones (Western Carpathians, Slovakia): tectonic controls over a growing orogenic wedge

The Pieniny Klippen Belt and neighbouring zones of the Western Carpathians represent an ancient accretionary wedge that developed during the meso-Alpidic (Coniacian–Eocene) tectonic epoch. After an overview of the extensive literature data, the authors present an interpretation of the synorogenic sedimentary record of these zones as being related to various environments of the foreland basin system consisting of the trench-foredeep and wedge-top depositional areas. The peripheral trench-foredeep depozones migrated from the South Penninic-Vahic oceanic realm towards the Oravic continental fragment in an intra-Penninic position, where the synorogenic deposits were laid down with coarsening- and thickening-upward trends before being overthrust by the propagating orogenic wedge tip. The development of wedge-top, piggyback basins (Gosau Supergroup) was controlled by the dynamics of the underlying wedge, composed of frontal elements of the Fatric and Hronic cover nappe systems of the Central Western Carpathians (Austroalpine units). Several compressional and extensional events are documented in the complex sedimentary and structural rock records within the wedge and related basins. The successive transgressive-regressive depositional cycles and corresponding deformation stages are interpreted in terms of a dynamic accretionary wedge that maintained the critical taper only transiently. The supercritical taper states are reflected in regression, shallowing and erosion in the wedge-top area, while the trench was supplied with large amounts of clastics by various gravity-flow types. On the other hand, the collapse stages tending to subcritical wedge taper are indicated by widespread marine transgressions or ingressions in the wedge-top area and a general deepening of all basins to bathyal conditions. Accordingly, the evolution of the entire trench-foredeep and wedge-top basin systems was principally controlled by the complex interplay of the regional tectonic evolution of the Alpine-Carpathian orogenic system, local wedge dynamics and eustatic sea-level fluctuations.

Petrology and geochemistry of a peridotite body in Central- Carpathian Paleogene sediments (Sedlice, eastern Slovakia)

Abstract We studied representative samples from a peridotite body situated NE of Sedlice village within the Central- Carpathian Paleogene sediments in the Central Western Carpathians. The relationship of the peridotite to the surrounding Paleogene sediments is not clear. The fractures of the brecciated peridotite margin are healed with secondary magnesite and calcite. On the basis of the presented bulk-rock and electron microprobe data, the wt. % amounts of mineral phases were calculated. Most of calculated “modal” compositions of this peridotite corresponds to harzburgites composed of olivine (∼70-80 wt. %), orthopyroxene (∼17-24 wt. %), clinopyroxene ( < 5 wt. %) and minor spinel ( < 1 wt. %). Harzburgites could originate from lherzolitic protoliths due to a higher degree of partial melting. Rare lherzolites contain porphyroclastic 1-2 mm across orthopyroxene (up to 25 wt. %), clinopyroxene (∼ 5-8 wt. %) and minor spinel ( < 0.75 wt. %). On the other hand, rare, olivine-rich dunites with scarce orthopyroxene porphyroclasts are associated with harzburgites. Metamorphic mineral assemblage of low-Al clinopyroxene (3), tremolite, chrysotile, andradite, Cr-spinel to chromite and magnetite, and an increase of fayalite component in part of olivine, indicate low-temperature metamorphic overprint. The Primitive Mantle normalized whole-rock REE patterns suggest a depleted mantle rock-suite. An increase in LREE and a positive Eu anomaly may be consequence of interactive metamorphic fluids during serpentinization. Similar rocks have been reported from the Meliatic Bôrka Nappe overlying the Central Western Carpathians orogenic wedge since the Late Cretaceous, and they could be a potential source of these peridotite blocks in the Paleogene sediments.

Constraining exhumation pathway in an accretionary wedge by (U-Th)/He thermochronology—Case study on Meliatic nappes in the Western Carpathians

This study reconstructs the late stages in the exhumation history of a nappe derived from the Meliatic accretionary wedge in the Western Carpathians by means of zircon and apatite (U-Th)/He dating. The Meliatic accretionary wedge formed due to the closure of the Neotethyan Triassic–Jurassic Meliata–Hallstatt Ocean in the Late Jurassic. The studied fragments of the blueschist-bearing Meliatic Bôrka Nappe were metamorphosed at low-temperature and high- to medium-pressure conditions at ca. 160–150Ma and included into the accretionary wedge. The time of the accretionary wedge formation constrains the beginning of the Bôrka Nappe northward thrusting over the Gemeric Unit of the evolving Central Western Carpathians (CWC) orogenic wedge. The zircon (U-Th)/He data on four samples recorded three evolutionary stages: (i) cooling through the ∼180°C isotherm at 130–120Ma related to starting collapse of the accretionary wedge, following exhumation of the high-pressure slices in the Meliatic accretionary wedge; (ii) postponed exhumation and cooling of some fragments through the ∼180°C isotherm from 115 to 95Ma due to ongoing collapse of this wedge; and (iii) cooling from 80 to 65Ma, postdating the thrusting (∼100–80Ma) of the Bôrka Nappe slices during the Late Cretaceous compression related to formation of the CWC orogenic wedge. The third stage already documents cooling of the Meliatic Bôrka Nappe slices in the CWC orogenic wedge. The apatite (U-Th)/He data may indicate cooling of a Bôrka Nappe slice to near-surface temperatures at ∼65Ma. The younger AHe age clusters indicate that at least one, or possibly two, reheating events could have occurred in the longer interval from ∼40 to ∼10Ma during the Oligocene–Miocene. These were related to sedimentary burial and/or the magmatism as documented in other parts of the CWC.

Cretaceous—Quaternary tectonic evolution of the Tatra Mts (Western Carpathians): constraints from structural, sedimentary, geomorphological, and fission track data

Abstract The Tatra Mts area, located in the northernmost part of Central Western Carpathians on the border between Slovakia and Poland, underwent a complex Alpine tectonic evolution. This study integrates structural, sedimentary, and geomorphological data combined with fission track data from the Variscan granite rocks to discuss the Cretaceous to Quaternary tectonic and landscape evolution of the Tatra Mts. The presented data can be correlated with five principal tectonic stages (TS), including neotectonics. TS-1 (~95-80 Ma) is related to mid-Cretaceous nappe stacking when the Tatric Unit was overlain by Mesozoic sequences of the Fatric and Hronic Nappes. After nappe stacking the Tatric crystalline basement was exhumed (and cooled) in response to the Late Cretaceous/Paleogene orogenic collapse followed by orogen-parallel extension. This is supported by 70 to 60 Ma old zircon fission track ages. Extensional tectonics were replaced by transpression to transtension during the Late Paleocene to Eocene (TS-2; ~80-45 Ma). TS-3 (~45-20 Ma) is documented by thick Oligocene-lowermost Miocene sediments of the Central Carpathian Paleogene Basin which kept the underlying Tatric crystalline basement at elevated temperatures (ca. > 120 °C and < 200 °C). The TS-4 (~20-7 Ma) is linked to slow Miocene exhumation rate of the Tatric crystalline basement, as it is indicated by apatite fission track data of 9-12 Ma. The final shaping of the Tatra Mts has been linked to accelerated tectonic activity since the Pliocene (TS-5; ~7-0 Ma).

Quartz-apatite-REE phosphates-uraninite vein mineralization near Čučma (eastern Slovakia): a product of early Alpine hydrothermal activity in the Gemeric Superunit, Western Carpathians

The quartz veins with primary fluorapatite, xenotime-(Y), monazite-(Ce) to monazite-(Nd), uraninite, and secondary florencite-(Ce) and goyazite occur in Lower Devonian metavolcano-sedimentary sequence of the Gelnica Group, Gemeric Superunit, the Central Western Carpathians (eastern Slovakia). They represent an example of hydrothermal REE–U mineralization. Fluorapatite forms parallel bands of columnar crystals (≤ 3 cm) in massive quartz. Monazite(Ce) to (Nd) shows a near end-member composition with very small amounts of cheralite and huttonite components. Widespread xenotime-(Y) forms colloform aggregates or irregular aggregates in association with fluorapatite and monazite. Uraninite electron-microprobe U–Pb dating gave the average age of 207 ± 2 Ma (n = 16, 2σ), which is consistent with formation of the U mineralization in the Gemeric Superunit (e.g., Kuriskova uranium deposit) during early Alpine hydrothermal activity.

Stratigraphic position of alkaline volcanic rocks in the autochthonous cover of the High-Tatric Unit (Western Tatra Mts., Central Western Carpathians, Slovakia)

Biostratigraphic investigations of carbonate strata that sandwich volcanic rocks and studies of the volcanic rocks were made along five composite lithological sections across the Upper Jurassic-Lower Cretaceous carbonate rocks of autochthonous cover of the High-Tatric Unit in the Osobitá peak area of the Western Tatra Mts. A carbonate microbreccia that consists almost exclusively of limestone clasts containing calpionellids occurs immediately below the volcanics. The youngest identified microfossil Calpionella elliptica Cadisch in the individual limestone clasts showed the age of breccia formation to be younger than late Early-early Middle Berriasian. The volcanic rocks are overlain by the Osobitá Limestone Formation, which in the lowermost horizons consists of a few metres thick crinoidal limestone containing the foraminifers Meandrospira favrei (Charollais, Brönnimann & Zaninetti), Sabaudia minuta Hofker and Montsalevia salevensis (Charollais, Brönnimann & Zaninetti) indicating a Late Valanginian-Early Hauterivian age. The biostratigraphical and sedimentological data obtained show that volcanism took place in several phases. Less intense phases of volcanism are recorded as thin tuffitic laminae within the upper parts of the Tithonian-early Mid Berriasian Sobótka Limestone Member and as fragments of volcanic rock in the carbonate breccia. The main phase(s) of volcanism took place during the Late Berriasian-?Early Valanginian.

Late Cretaceous–Cenozoic thermal evolution of the northern part of the Central Western Carpathians (Slovakia): revealed by zircon and apatite fission track thermochronology

Abstract Tectono-thermal evolution of the northern part of Central Western Carpathians (Slovakia) was revealed by zircon and apatite fission track thermochronology of Neogene deposits, volcanic rocks, and crystalline basement. New fission track ages combined with previous geochronological data are correlated with main tectonic events and important palaeogeographic changes. (1) The palaeo-Alpine burial to more than 10 km depths, heating (> 320 °C) and low-grade metamorphism of the crystalline basement was caused by crustal thickening due to nappe stacking driven by the collisional processes (~ 90–75 Ma). (2) Extensional collapse and exhumation of basement complexes during the Late Cretaceous to Middle Eocene (~ 75–40 Ma). (3) The extension process resulted in a new sedimentary cycle of the Central Carpathian Palaeogene Basin (~ 40–25 Ma) in the northern part of the Central Western Carpathians. During the ensuing burial under the thick sedimentary cover, the crystalline basement of the northern zone resided at ‘hotter’ conditions (ca. > 120 °C and

Earthquake‐affected development of a travertine ridge

AbstractAlthough the relation between travertine and tectonics is commonly accepted, the influence of seismic activity on the internal structures and facies development of travertine has not been examined extensively. The aim of this paper was to unravel the impact of seismic shocks on the anatomy of a travertine mound. Dreveník travertine in the Central Western Carpathians of Slovakia was studied using detailed facies analysis, based on fieldwork coupled with microscope and stable isotope studies. The travertine formed a ridge fed by ascending water of deep circulation, charged with CO2 of geogenic origin. The location of the ridge over an impermeable Palaeogene flysch complex and the stable isotope composition of the travertine support the above interpretation. The ridge is composed of crystalline crust travertine, lithoclast travertine, fine‐grained lithoclast travertine, paper‐thin raft travertine and coated bubble travertine. The travertine underwent brittle deformations resulting in formation of fissures and intraclast breccia. Several lines of evidence prove that the deformations occurred during travertine deposition: (i) breccias are covered by undisturbed layers of travertine; (ii) ground fissures are filled with younger travertine; and (iii) calcite filling fissures and cementing breccia crystallized from water with the same isotopic composition as the travertine. The deformations resulted from seismic shocks which also triggered rockfall avalanches that led to the destruction of the upper part of the travertine slope and deposition of lithoclast travertine on its lower parts. Local hydrological conditions changed after the shocks, favouring ponding of water which, in turn, led to formation of paper‐thin raft travertine over lithoclast travertine. Thus, earthquakes exerted an important control on the development of the studied travertine mound. It is plausible that earthquakes have impacted other travertine mounds and influenced their facies development.

Geochronology and petrogenesis of granitoid rocks from the Goryczkowa Unit, Tatra Mountains (Central Western Carpathians)

Abstract The geochemical characteristics as well as the LA-MC-ICP-MS U-Pb zircon age relationship between two granitoid suites found in the Goryczkowa crystalline core in the Western Tatra Mountains were studied. The petrological investigations indicate that both granitoid suites were emplaced at medium crustal level, in a VAG (volcanic arc granites) tectonic setting. However, these suites differ in source material melted and represent two different magmatic stages: suite 1 represents a high temperature, oxidized, pre-plate collision intrusion, emplaced at ca. 371 Ma while suite 2 is late orogenic/anatectic magma, which intruded at ca. 350 Ma. These data are consistent with a period of intensive magmatic activity in the Tatra Mountain crystalline basement. The emplacement of granitoids postdates the LP-HT regional metamorphism/ partial melting at ca. 387 Ma and at 433-410 Ma, imprinted in the inherited zircon cores.

A putative upupiform bird from the Early Oligocene of the Central Western Carpathians and a review of fossil birds unearthed in Slovakia

An isolated hind limb of a miniature bird from an Early Oligocene locality (30–34 Ma) near Bystré (Slovakia) is described and analyzed. The tarsometatarsus (TMT) of the specimen is remarkably short relative to the tibiotarsus. When relative length ratios of the bones are compared with a sample of 29 extant and extinct birds with short metatarsi, the specimen variably clusters with some alcedinids, coraciids and trochilids. Log-clusters give less ambiguous results and indicate significant proximity of the Bystré specimen to the extinct messelirrisorids (Upupiformes) and the recent acledinids (Coraciiformes). With regard to morphological details, such as those of the first metatarsal, II-IV metatarsal trochleae, intertrochlear incisurae and phalanges, the Slovak specimen shows a combination of features, which are distributed among recent upupiforms and coraciiforms as well as extinct upupiforms (Messelirrisor) and apodiforms (Eocypselus, Parargornis). Taken together, the metric and morphological data sets suggest that the specimen from Bystré is a coraciiform sensu lato rather than an apodiform bird. Within the Coraciiformes, the robust trochlea of MT-I with expanded dorsal shelf, the large medial and slit-like lateral intertrochlear incisura, and the long hindtoe suggest upupiform rather than alcedinid relationships.

Foraminiferal and radiolarian biostratigraphy of the youngest (Late Albian through Late Cenomanian) sediments of the Tatra massif, Central Western Carpathians

Abstract Bąk, K. and Bąk M. 2013. Foraminiferal and radiolarian biostratigraphy of the youngest (Late Albian through Late Cenomanian) sediments of the Tatra massif, Central Western Carpathians. Acta Geologica Polonica, 63 (2), 223-237. Warszawa. The foraminiferal and radiolarian biostratigraphy of selected sections of the Zabijak Formation, the youngest sediments of the Tatra massif (Central Western Carpathians), have been studied. Benthic foraminifers, mainly agglutinated species, occur abundantly and continuously throughout the studied succession, while planktic foraminifers are generally sparse. Five planktic and two benthic foraminiferal zones have been recognized. The marly part of the Zabijak Formation comprises the Pseudothalmanninella ticinensis (Upper Albian) through the Rotalipora cushmani (Upper Cenomanian) planktic foraminiferal zones, and the Haplophragmoides nonioninoides and Bulbobaculites problematicus benthic foraminiferal zones. The radiolarians were recognized exclusively in the Lower Cenomanian part of the formation.

U-Pb zircon age of the youngest magmatic activity in the High Tatra granites (Central Western Carpathians)

Abstract Detailed cathodoluminescence (CL) imaging of zircon crystals, coupled with Laser Ablation Multi-Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) U-Pb zircon dating was used to develop new insights into the evolution of granitoids from the High Tatra Mountains. The zircon U-Pb results show two distinct age groups (350±5 Ma and 337±6 Ma) recorded from cores and rims domains, respectively. Obtained results point that the last magmatic activity in the Tatra granitoid intrusion occurred at ca. 330 Ma. The previously suggested age of 314 Ma reflects rather the hydrothermal activity and Pb-loss, coupled with post-magmatic shearing.

A comparison of two orogenic margins: central Scandinavian Caledonides and western Outer Carpathians

A comparison of two orogenic margins: central Scandinavian Caledonides and western Outer Carpathians

New paleomagnetic results from the Upper Cretaceous red marls of the Pieniny Klippen Belt, Western Carpathians: Evidence for general CCW rotation and implications for the origin of the structural arc formation

The Pieniny Klippen Belt (PKB) is a narrow arcuate structure separating the Central and Outer Western Carpathians formed during several Cenozoic deformational stages. The primary aim of this study was to obtain paleomagnetic constraints for the mechanism of formation of the arc. We investigate Albian–Santonian red pelagic marls from 14 localities, distributed along a strike length of ca. 400km. AMS measurements reveal a pattern characteristic of weakly deformed sedimentary rocks and magnetic lineations do not correlate with the general strike of the PKB. Paleomagnetic analysis revealed well defined hematite-based ancient magnetization components at 13 localities, which are dated using fold- and inclination tests. A within-locality fold test is negative for two localities exhibiting large CCW rotations of similar magnitude situated at the two ends of the PKB. Remanences of pre-folding age were documented for 11 localities, with an overall mean paleomagnetic direction of D=311°, I=53°, and α95=11°. The indicated general CCW rotation most probably took place during the Miocene, together with Western Central and Outer Carpathians. Paleolatitudes for the PKB indicate a considerable separation from the southern margin of stable Europe leaving space for coordinated rotation. A paleomagnetic oroclinal test involving all localities with primary magnetizations was negative. When localities with monoclinal steep dips are omitted due to possible declination bias, the overall mean paleomagentic direction does not change significantly, but correlation is observed between the general trend of the PKB and the paleomagnetic declinations. Thus, we conclude that the present shape of the arc can be partly due to oroclinal bending. This must have happened before Oligocene since paleomagnetic declinations for neighboring Paleogene basins in the Central and Outer Western Carpathians reveal a uniform CCW rotation of ca. 50° magnitude, irrespective of the position of the localities in relation to the Carpathian arc.

Re-Os and U-Th-Pb dating of the Rochovce granite and its mineralization (Western Carpathians, Slovakia)

Abstract The subsurface Rochovce granite intrusion was emplaced into the contact zone between two principal tectonic units (the Veporic Unit and the Gemeric Unit) of the Central Western Carpathians (CWC), Slovakia. The Cretaceous age of this granite and its Mo-W mineralization is shown using two independent methods: U-Pb on zircon and Re-Os on molybdenite. The studied zircons have a typical homogeneous character with oscillatory zoning and scarce restite cores. SHRIMP U-Pb data provide an age of 81.5 ± 0.7 Ma, whereas restite cores suggest a latest Neoproterozoic-Ediacaran age (~565 Ma) source. Zircon εHf(81) values -5.2 to + 0.2 suggest a lower crustal source, whereas one from the Neoproterozoic core εHf(565)= + 7.4 call for the mantle influenced old precursor. Two molybdenite- bearing samples of very different character affirm a genetic relation between W-Mo mineralization and the Rochovce granite. One sample, a quartz-molybdenite vein from the exocontact (altered quartz-sericite schist of the Ochtiná Formation), provides a Re-Os age of 81.4 ± 0.3 Ma. The second molybdenite occurs as 1-2 mm disseminations in finegrained granite, and provides an age of 81.6 ± 0.3 Ma. Both Re-Os ages are identical within their 2-sigma analytical uncertainty and suggest rapid exhumation as a consequence of post-collisional, orogen-parallel extension and unroofing. The Rochovce granite represents the northernmost occurrence of Cretaceous calc-alkaline magmatism with Mo-W mineralization associated with the Alpine-Balkan-Carpathian-Dinaride metallogenic belt.

Tectonic control of tufa occurrences in the Podhale Synclinorium (Central Western Carpathians, southern Poland)

Tufas in the Podhale Synclinorium (southern Poland) occur as encrustations on moss and plant remains, crusts, porous, clastic and massive tufas. The tufas are almost entirely composed of calcite with small admixture of quartz, illite and chlorite. These deposits indicate the biotic and/or abiotic origin of calcium carbonate. The tufas occur in the vicinity of map-scale and minor fault zones. They precipitate near fissure springs linked with small faults and fault rocks or seepages along them. Exposures with tufas occur along several oblique and lateral zones. The oblique zones are related to Bialka and Bialy Dunajec faults that have normal components. The lateral zones of tufa occurrences are connected with lateral faults limiting the “zone of beds with gentle dips” and extensional brittle structures within the hinge of the synclinorium. The relationship of the tufa with brittle extensional structures suggests Quaternary tectonic activity of the Podhale Synclinorium that can be explained by continued uplift in the area studied.

Biting midges of the genus Dasyhelea Kieffer (Diptera: Ceratopogonidae) in Poland

Abstract . This article reviews 30 species of biting midges of the genus Dasyhelea that are known to occur in Poland. Diagnoses and detailed descriptions of adults are provided for all Polish species, as well as keys (based mainly on males) for the identification of subgenera and their included species. Dasyhelea excellentis BORKENT, 1997 is recognized as a new junior synonym of Dasyhelea bifida ZILAHI-SEBESS, 1936 (syn. n.) and Dasyhelea lugensis BRODSKAYA, 1995 as a new junior synonym of Dasyhelea caesia REMM, 1993 (syn. n.). Among the Polish biting midge fauna, most species of the genus Dasyhelea are primarily arboreal, widely distributed Palaearctic species. The most species-rich samples were collected in the following regions: Eastern Baltic Lakelands (19 spp.), Southern Baltic Lakelands (16 spp.), Southern Baltic Coastlands (14 spp.) and Central Western Carpathians (12 spp.). The larvae were found in sap and tree holes, water accumulated in gutters and sinks, moist soil near fresh- and saltwater bodies, and peat bogs. Adults are known to visit flowers for nectar, and 16 Polish species were found on umbelliferous flowers.

Beryl composition and evolution trends: an example from granitic pegmatites of the beryl-columbite subtype, Western Carpathians, Slovakia

*Corresponding author Beryl is an uncommon but characteristic mineral of Hercynian granitic pegmatites associated with S-type granites– granodiorites of the Bratislava and Bojna massifs, Tatric Unit, Central Western Carpathians (SW Slovakia). Beryl represents the only essential rare-element phase in majority of the pegmatites, whereas accessory Nb–Ta–(Sn) oxide minerals occur in the most evolved ones (Moravany nad Vahom, Jezuitske Lesy). Beryl forms columnar pale green crystals on the boundary between blocky K-feldspar zone and muscovite plus quartz core (beryl I) or locally in saccharoidal and cleavelandite albite unit (beryl II). The EMPA, LA-ICP-MS and XRD data show mostly the presence of common Li, Cs-poor beryl with variable amounts of Na and occasionally small Fe, Mg-enriched domains (up to 3.5 wt. % FeO and 1.8 wt. % MgO), with dominant channel–octahedral substitution represented by the Na(Fe 2+ ,Mg) -1 Al -1 exchange. Beryl of the most evolved pegmatites contains moderately elevated Li (up to 5600 ppm; Moravany nad Vahom) or Cs contents (up to 9800 ppm, 1 to 2 wt. % Cs 2 O in some zones; Jezuitske Lesy), which indicates also a possibility of channel–tetrahedral substitutions. A common patchy internal zoning of primary magmatic beryl I crystals represents a late-magmatic to subsolidus, partial dissolution-reprecipitation phenomenon. On the contrary, crystals of beryl II show relatively homogeneous internal texture and lower content of Cs than associated beryl I. Consequently, compositional variations and internal texture of the beryl demonstrate magmatic to subsolidus evolution of less fractionated, beryl– columbite subtype populations of the granitic pegmatites. The primary evolution trend of beryl is characterized by increasing Cs and Cs/Na with decreasing Mg and Mg/Fe from less evolved to more fractionated pegmatites. However, a secondary evolution trend, probably connected with post-magmatic partial dissolution-reprecipitation, shows decreasing Cs and increasing Mg/Fe in the beryl.

Pegmatitic Nb-Ta oxide minerals in alluvial placers from Limbach, Bratislava Massif, Western Carpathians, Slovakia: compositional variations and evolutionary trend

*Corresponding author Niobium-tantalum mineral assemblage of granitic pegmatite origin was found in alluvial placers near Limbach, the Bratislava granitic massif, Male Karpaty Mountains, Central Western Carpathians, southwest Slovakia. The most widespread mineral is ferrocolumbite to ferrotantalite, rarely manganocolumbite to manganotantalite I [at. Mn/(Mn + Fe) = 0.17–0.52 and Ta/(Ta + Nb) = 0.19–0.70] shows primary magmatic, fine to coarse, regular oscillatory zoning with an evolutionary trend indicating a moderate degree of fractionation, analogous to beryl–columbite subtype of rare-element granitic pegmatites. On the contrary, irregular oscillatory and patchy zoning of ferrocolumbite to manganotantalite II [Mn/(Mn + Fe) = 0.17–0.66, Ta/(Ta + Nb) = 0.16–0.81] together with precipitation of anhedral Ta-rich intergrowths and inclusions of ferrotapiolite [Mn/(Mn + Fe = 0.05–0.07, Ta/(Ta + Nb) = 0.87–0.93], Ta>Nb-rich rutile [Mn/(Mn + Fe) = 0.02–0.03, Ta/(Ta + Nb) = 0.80–0.86], Sn-rich ixiolite [Mn/(Mn + Ta) = 0.40–0.41, Ta/(Ta + Nb) = 0.81] and uraninite + uranmicrolite [Ta/(Ta + Nb) = 0.81–0.94] indicates their subsolidus origin.