MTA ELTE Volcanology Research Group

Budapest, Hungary

MTA ELTE Volcanology Research Group

Budapest, Hungary

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Batki A.,MTA ELTE Volcanology Research Group | Pal-Molnar E.,MTA ELTE Volcanology Research Group | Pal-Molnar E.,University of Szeged | Dobosi G.,MTA ELTE Volcanology Research Group | And 2 more authors.
Lithos | Year: 2014

Camptonite dykes intrude the rift-related Mesozoic igneous body of the Ditrǎu Alkaline Massif, Eastern Carpathians, Romania. We present and discuss mineral chemical data, major and trace elements, and the Nd isotopic compositions of the dykes in order to define their nature and origin. The dykes are classified as the clinopyroxene-bearing (camptonite-I) and clinopyroxene-free (camptonite-II) varieties. Camptonite-I consists of aluminian-ferroan diopside phenocrysts accompanied by kaersutite, subordinate Ti-rich annite, albite to oligoclase and abundant calcite-albite ocelli. Camptonite-II comprises K-rich hastingsite to magnesiohastingsite, Ti-rich annite, albite to andesine, abundant accessory titanite and apatite, and silicate ocelli filled mainly with plagioclase (An4-34).Age-corrected 143Nd/144Nd ratios vary from 0.51258 to 0.51269. The high εNd values of +4.0 to +6.1 which are consistent with intra-plate composition, together with light rare earth element (LREE), large ion lithophile element (LILE) and high field strength element (HFSE) enrichment in the camptonites is ascribed to the formation of small melt batches of a metasomatised sub-lithospheric mantle source. The presence of an asthenospheric 'high μ' ocean island basalt (HIMU-OIB)-type mantle component in the source region has also been revealed. A 1-4% degree of partial melting of an enriched garnet lherzolite mantle source containing pargasitic amphibole followed by fractionation is inferred to have been involved in the generation of the camptonites. They are deduced to be parental melts to the Ditrǎu Alkaline Massif. •Ditrǎu camptonites have been generated by 1-4% partial melting of an enriched mantle.•The source region is garnet lherzolite containing 4% of pargasitic amphibole.•The source enrichment is attributed to a sub-lithospheric metasomatic zone.•An asthenospheric HIMU-OIB-type mantle component was involved in the melt generation.•They are deduced to be parental melts to the Ditrǎu Alkaline Massif. © 2014 Elsevier B.V.

Harangi S.,MTA ELTE Volcanology Research Group | Harangi S.,Eötvös Loránd University | Jankovics M.E.,MTA ELTE Volcanology Research Group | Jankovics M.E.,University of Szeged | And 7 more authors.
International Journal of Earth Sciences | Year: 2015

Alkaline basaltic volcanism has been taking place in the Carpathian–Pannonian region since 11 Ma and the last eruptions occurred only at 100–500 ka. It resulted in scattered low-magma volume volcanic fields located mostly at the margins of the Pannonian basin. Many of the basalts have compositions close to those of the primitive magmas and therefore can be used to constrain the conditions of the magma generation. Low-degree (2–3 %) melting could occur in the convective asthenosphere within the garnet–spinel transition zone. Melting started at about 100 km depth and continued usually up to the base of the lithosphere. Thus, the final melting pressure could indicate the ambient lithosphere–asthenosphere boundary. The asthenospheric mantle source regions of the basalts were heterogeneous, presumably in small scale, and included either some water or pyroxenite/eclogite lithology in addition to the fertile to slightly depleted peridotite. Based on the prevailing estimated mantle potential temperature (1,300–1,400 °C) along with the number of further observations, we exclude the existence of mantle plume or plume fingers beneath this region. Instead, we propose that plate tectonic processes controlled the magma generation. The Pannonian basin acted as a thin spot after the 20–12 Ma syn-rift phase and provided suction in the sublithospheric mantle, generating asthenospheric flow from below the adjoining thick lithospheric domains. A near-vertical upwelling along the steep lithosphere–asthenosphere boundary beneath the western and northern margins of the Pannonian basin could result in decompressional melting producing low-volume melts. The youngest basalt volcanic field (Perşani) in the region is inferred to have been formed due to the dragging effect of the descending lithospheric slab beneath the Vrancea zone that could result in narrow rupture at the base of the lithosphere. Continuation of the basaltic volcanism cannot be excluded as inferred from the still fusible condition of the asthenospheric mantle. This is reinforced by the detected low-velocity seismic anomalies in the upper mantle beneath the volcanic fields. © 2014, Springer-Verlag Berlin Heidelberg.

Kiss B.,MTA ELTE Volcanology Research Group | Kiss B.,Eötvös Loránd University | Kiss B.,University of Szeged | Harangi S.,MTA ELTE Volcanology Research Group | And 5 more authors.
Contributions to Mineralogy and Petrology | Year: 2014

Ciomadul is the youngest volcano in the Carpathian-Pannonian region produced crystal-rich high-K dacites that contain abundant amphibole phenocrysts. The amphiboles in the studied dacites are characterized by large variety of zoning patterns, textures, and a wide range of compositions (e.g., 6.4-15 wt% Al2O3, 79-821 ppm Sr) often in thin-section scale and even in single crystals. Two amphibole populations were observed in the dacite: low-Al hornblendes represent a cold (<800 °C) silicic crystal mush, whereas the high-Al pargasites crystallized in a hot (>900 °C) mafic magma. Amphibole thermobarometry suggests that the silicic crystal mush was stored in an upper crustal storage (~8-12 km). This was also the place where the erupted dacitic magma was formed during the remobilization of upper crustal silicic crystal mush body by hot mafic magma indicated by simple-zoned and composite amphiboles. This includes reheating (by ~200 °C) and partial remelting of different parts of the crystal mush followed by intensive crystallization of the second mineral population (including pargasites). Breakdown textures of amphiboles imply that they were formed by reheating in case of hornblendes, suggesting that pre-eruptive heating and mixing could take place within days or weeks before the eruption. The decompression rim of pargasites suggests around 12 days of magma ascent in the conduit. Several arc volcanoes produce mixed intermediate magmas with similar bimodal amphibole cargo as the Ciomadul, but in our dacite the two amphibole population can be found even in a single crystal (composite amphiboles). Our study indicates that high-Al pargasites form as a second generation in these magmas after the mafic replenishment into a silicic capture zone; thus, they cannot unambiguously indicate a deeper mafic storage zone beneath these volcanoes. The simple-zoned and composite amphiboles provide direct evidence that significant compositional variations of amphiboles do not necessarily mean variation in the pressure of crystallization even if the Al-tschermak substitution can be recognized, suggesting that amphibole barometers that consider only amphibole composition may often yield unrealistic pressure variation. © 2014 Springer-Verlag Berlin Heidelberg.

Halmos L.,University of Szeged | Bozso G.,University of Szeged | Pal-Molnar E.,University of Szeged | Pal-Molnar E.,MTA ELTE Volcanology Research Group
Soil and Water Research | Year: 2015

Adsorption properties of Cu, Ni, and Zn in alkaline sediments of Lake Fehér at Szeged (Hungary) were investigated. The effects of pollution of these three chosen phytotoxic elements in sodic sediments were primarily examined. These elements are strongly adsorbed in the soils and sediments with relatively high pH values for a long time without any influence on the geochemical processes. However, the salinization (indicated by the global climate change) of soils and sediments can strongly change the original geochemical status. For the adsorption experiments, the horizons with the highest organic matter contents were selected from two profiles. The pH, electrical conductivity (EC), particle size distribution, carbonate content, quality and quantity of organic matter, and clay mineral content of the selected samples were also determined. Efficiency of the adsorption is reduced in Cu > Zn>Ni and Cu>Ni > Zn order based on the calculated maximum and specific adsorption values. The adsorption properties of heavy metals are dependent on the content of soil constituents. The results showed that Cu has the highest but not the same affinity to each of the sorbent materials. Ni is strongly while Zn is less bounded to the organic matter. In most cases the results showed that the most effective fixative soil constituent is carbonate, followed by clay minerals and, last, organic matter regarding to the investigated elements.

Jankovics M.E.,Eötvös Loránd University | Dobosi G.,MTA ELTE Volcanology Research Group | Dobosi G.,Hungarian Academy of Sciences | Embey-Isztin A.,Hungarian Natural History Museum | And 6 more authors.
Bulletin of Volcanology | Year: 2013

The last eruptions of the monogenetic Bakony-Balaton Highland Volcanic Field (western Pannonian Basin, Hungary) produced unusually crystal- and xenolith-rich alkaline basalts which are unique among the alkaline basalts of the Carpathian-Pannonian Region. Similar alkaline basalts are only rarely known in other volcanic fields of the world. These special basaltic magmas fed the eruptions of two closely located volcanic centres: the Bondoró-hegy and the Füzes-tó scoria cone. Their uncommon enrichment in diverse crystals produced unique rock textures and modified original magma compositions (13.1-14.2 wt.% MgO, 459-657 ppm Cr, and 455-564 ppm Ni contents). Detailed mineral-scale textural and chemical analyses revealed that the Bondoró-hegy and Füzes-tó alkaline basaltic magmas have a complex ascent history, and that most of their minerals (~30 vol.% of the rocks) represent foreign crystals derived from different levels of the underlying lithosphere. The most abundant xenocrysts, olivine, orthopyroxene, clinopyroxene, and spinel, were incorporated from different regions and rock types of the subcontinental lithospheric mantle. Megacrysts of clinopyroxene and spinel could have originated from pegmatitic veins/sills which probably represent magmas crystallized near the crust-mantle boundary. Green clinopyroxene xenocrysts could have been derived from lower crustal mafic granulites. Minerals that crystallized in situ from the alkaline basaltic melts (olivine with Cr-spinel inclusions, clinopyroxene, plagioclase, and Fe-Ti oxides) are only represented by microphenocrysts and overgrowths on the foreign crystals. The vast amount of peridotitic (most common) and mafic granulitic materials indicates a highly effective interaction between the ascending magmas and wall rocks at lithospheric mantle and lower crustal levels. However, fragments from the middle and upper crust are absent from the studied basalts, suggesting a change in the style (and possibly rate) of magma ascent in the crust. These xenocryst- and xenolith-rich basalts yield divers tools for estimating magma ascent rate that is important for hazard forecasting in monogenetic volcanic fields. According to the estimated ascent rates, the Bondoró-hegy and Füzes-tó alkaline basaltic magmas could have reached the surface within hours to few days, similarly to the estimates for other eruptive centres in the Pannonian Basin which were fed by "normal" (crystal and xenoliths poor) alkaline basalts. © 2013 Springer-Verlag Berlin Heidelberg.

Harangi S.,MTA ELTE Volcanology Research Group | Harangi S.,Eötvös Loránd University | Sagi T.,MTA ELTE Volcanology Research Group | Sagi T.,Eötvös Loránd University | And 2 more authors.
Lithos | Year: 2013

The Perşani volcanic field is a low-volume flux monogenetic volcanic field in the Carpathian-Pannonian region, eastern-central Europe. Volcanic activity occurred intermittently from 1200. ka to 600. ka, forming lava flow fields, scoria cones and maars. Selected basalts from the initial and younger active phases were investigated for major and trace element contents and mineral compositions. Bulk compositions are close to those of the primitive magmas; only 5-12% olivine and minor spinel fractionation occurred at 1300-1350. °C, followed by clinopyroxenes at about 1250. °C and 0.8-1.2. GPa. Melt generation occurred in the depth range from 85-90. km to 60. km. The estimated mantle potential temperature, 1350-1420. °C, is the lowest in the Pannonian Basin. It suggests that no thermal anomaly exists in the upper mantle beneath the Perşani area and that the mafic magmas were formed by decompression melting under relatively thin continental lithosphere. The mantle source of the magmas could be slightly heterogeneous, but is dominantly variously depleted MORB-source peridotite, as suggested by the olivine and spinel composition. Based on the Cr-numbers of the spinels, two coherent compositional groups (0.38-0.45 and 0.23-0.32, respectively) can be distinguished that correspond to the older and younger volcanic products. This indicates a change in the mantle source region during the volcanic activity as also inferred from the bulk rock major and trace element data. The younger basaltic magmas were generated by lower degree of melting, from a deeper and compositionally slightly different mantle source compared to the older ones. The mantle source character of the Perşani magmas is akin to that of many other alkaline basalt volcanic fields in the Mediterranean close to orogenic areas. The magma ascent rate is estimated based on compositional traverses across olivine xenocrysts using variations of Ca content. Two heating events are recognized; the first one lasted about 1.3. years implying heating of the lower lithosphere by the uprising magma, whereas the second one lasted only 4-5. days, which corresponds to the time of magma ascent through the continental crust. The alkaline mafic volcanism in the Perşani volcanic field could have occurred as a response to the formation of a narrow rupture in the lower lithosphere, possibly as a far-field effect of the dripping of dense continental lithospheric material beneath the Vrancea zone. Upper crustal extensional stress-field with reactivation of normal faults at the eastern margin of the Transylvanian basin could enhance the rapid ascent of the mafic magmas. © 2013 Elsevier B.V.

Petrik A.,Eötvös Loránd University | Beke B.,Hungarian Academy of Sciences | Fodor L.,Hungarian Academy of Sciences | Lukacs R.,MTA ELTE Volcanology Research Group
Geologica Carpathica | Year: 2016

Extensive structural field observations and seismic interpretation allowed us to delineate 7 deformation phases in the study area for the Cenozoic period. Phase D1 indicates NW-SE compression and perpendicular extension in the Late Oligocene-early Eggenburgian and it was responsible for the development of a wedge-shaped Paleogene sequence in front of north-westward propagating blind reverse faults. D2 is represented by E-W compression and perpendicular extension in the middle Eggenburgian-early Ottnangian. The D1 and D2 phases resulted in the erosion of Paleogene suites on elevated highs. Phase D2 was followed by a counterclockwise rotation, described in earlier publications. When considering the age of sediments deformed by the syn-sedimentary D3 deformation and preliminary geochronological ages of deformed volcanites the time of the first CCW rotation can be shifted slightly younger (~17-16.5 Ma) than previously thought (18.5-17.5 Ma). Another consequence of our new timing is that the extrusional tectonics of the ALCAPA unit, the D2 local phase, could also terminate somewhat later by 1 Myr. D4 shows NE-SW extension in the late Karpatian-Early Badenian creating NW-SE trending normal faults which connected the major NNE-SSW trending sinistral faults. The D5 and D6 phases are late syn-rift deformations indicating E-W extension and NW-SE extension, respectively. D5 indicates syn-sedimentary deformation in the Middle Badenian-early Sarmatian and caused the synsedimentary thickening of mid-Miocene suites along NNE-SSW trending transtensional faults. D5 postdates the second CCW rotation which can be bracketed between ~16-15 Ma. This timing is somewhat older than previously considered and is based on new geochronological dates of pyroclastite rocks which were not deformed by this phase. D6 was responsible for further deepening of half-grabens during the Sarmatian. D7 is post-tilt NNW-SSE extension and induced the deposition of the 700 m thick Pannonian wedge between 11.6-8.92 Ma in the southern part of the study area. © 2016 Geologica Carpathica 2016.

Fintor K.,University of Szeged | Park C.,University of Hawaii at Manoa | Nagy S.,University of Szeged | Pal-Molnar E.,University of Szeged | And 2 more authors.
Meteoritics and Planetary Science | Year: 2014

We report an occurrence of hexagonal CaAl2Si2O8 (dmisteinbergite) in a compact type A calcium-aluminum-rich inclusion (CAI) from the CV3 (Vigarano-like) carbonaceous chondrite Northwest Africa 2086. Dmisteinbergite occurs as approximately 10 μm long and few micrometer-thick lath-shaped crystal aggregates in altered parts of the CAI, and is associated with secondary nepheline, sodalite, Ti-poor Al-diopside, grossular, and Fe-rich spinel. Spinel is the only primary CAI mineral that retained its original O-isotope composition (Δ17O ~ -24‰); Δ17O values of melilite, perovskite, and Al,Ti-diopside range from -3 to -11‰, suggesting postcrystallization isotope exchange. Dmisteinbergite, anorthite, Ti-poor Al-diopside, and ferroan olivine have 16O-poor compositions (Δ17O ~ -3‰). We infer that dmisteinbergite, together with the other secondary minerals, formed by replacement of melilite as a result of fluid-assisted thermal metamorphism experienced by the CV chondrite parent asteroid. Based on the textural appearance of dmisteinbergite in NWA 2086 and petrographic observations of altered CAIs from the Allende meteorite, we suggest that dmisteinbergite is a common secondary mineral in CAIs from the oxidized Allende-like CV3 chondrites that has been previously misidentified as a secondary anorthite. © The Meteoritical Society, 2014.

Harangi S.,MTA ELTE Volcanology Research Group | Harangi S.,Eötvös Loránd University | Lukacs R.,MTA ELTE Volcanology Research Group | Lukacs R.,University of Szeged | And 8 more authors.
Journal of Volcanology and Geothermal Research | Year: 2015

High-spatial resolution zircon geochronology was applied to constrain the timescales of volcanic eruptions of the youngest, mostly explosive volcanic phase of Ciomadul volcano (Carpathian-Pannonian region, Romania). Combined U-Th and (U-Th)/He zircon dating demonstrates that intermittent volcanic eruptions occurred in a time range of 56-32. ka. The reliability of the eruption dates is supported by concordant ages obtained from different dating techniques, such as zircon geochronology, radiocarbon analysis, and infrared stimulated luminescence dating for the same deposits. The new geochronological data suggest that volcanism at Ciomadul is much younger (<. ca. 200. ka) than previously thought (up to 600. ka). A dominantly explosive volcanic phase occurred after an apparent lull in volcanism that lasted for several 10's of ka, after a period of lava dome extrusion that defines the onset of the known volcanism at Ciomadul. At least four major eruptive episodes can be distinguished within the 56-32. ka period. Among them, relatively large (sub-plinian to plinian) explosive eruptions produced distal tephra covering extended areas mostly southeast from the volcano. The 38.9. ka tephra overlaps the age of the Campanian Ignimbrite eruption and has an overlapping dispersion axis towards the Black Sea region. The wide range of U-Th model ages of the studied zircons indicates prolonged existence of a low-temperature (<. 800. °C) silicic crystal mush beneath Ciomadul. The main zircon crystallization period was between ca. 100 and 200. ka, coeval with the older, mostly extrusive lava dome building stage of volcanism. Even the youngest U-Th model ages obtained for the outermost 4. μm rim of individual zircon crystals predate the eruption by several 10's of ka. The zircon age distributions suggest re-heating above zircon saturation temperatures via injection of hot mafic magmas prior to eruption. Intermittent intrusions of fresh magma could play a significant role in keeping the intrusive silicic magmatic reservoir in a partially melted for prolonged period. The previous history of Ciomadul suggests that melt-bearing crystal mush resided beneath the volcano, and was rapidly remobilized after a protracted (several 10's of ka) lull in volcanism to trigger several eruptions in a comparatively short time window. This classifies Ciomadul as a volcano with 'Potentially Active Magma Storage' (PAMS) which we propose to be common among the seemingly inactive volcanoes in volcanic arc regions. The potential for reactivation of these systems should be included into volcanic hazard assessments. © 2015 Elsevier B.V.

Jankovics M.E.,MTA ELTE Volcanology Research Group | Taracsak Z.,Eötvös Loránd University | Dobosi G.,MTA ELTE Volcanology Research Group | Dobosi G.,Debrecen University | And 5 more authors.
Lithos | Year: 2016

Clinopyroxene crystals of various origins occur in the unusually crystal- and xenolith-rich alkaline basalts of the Bondoró-hegy and the Füzes-tó scoria cone, which are the youngest eruptive centres in the Bakony-Balaton Highland Volcanic Field, western Pannonian Basin. The clinopyroxenes show diverse textural and zoning features as well as highly variable major and trace element chemistry. Xenocryst, megacryst and phenocryst crystal populations can be distinguished on the basis of their compositional differences. The trace element patterns of green clinopyroxene cores display a large range in composition and indicate that most of them have a metamorphic origin. Most of them were incorporated from lower crustal mafic granulite wall rocks, while only a few of them are of magmatic origin representing pyroxenite (Type II) cumulates. The colourless clinopyroxene xenocrysts reflect the texturally and geochemically diverse nature of the subcontinental lithospheric mantle beneath the studied area, mainly representing regions characterised by various stages of metasomatism. The colourless and green megacrysts are genetically related to each other, having crystallised as early and late crystallisation products, respectively, from petrogenetically related melts as part of a fractional crystallisation sequence. These melts represent earlier alkaline basaltic magmas (as represented by the Type II xenoliths), having stalled and crystallised near the crust–mantle boundary in the uppermost part of the mantle. This serves as evidence that the deep magmatic systems beneath monogenetic volcanic fields are complex, involving several phases of melt generation, accumulation and fractionation at variable depths. We show that in situ trace element analysis is necessary in order to unravel the origins and relationships of the diverse clinopyroxene populations. Such studies significantly contribute to our understanding of the ascent histories of alkaline basaltic magmas and provide information about the characteristics of the rocks that constitute the lithosphere. Additionally, the abundance of foreign crystals incorporated in the ascending basaltic magmas, and their potential for contamination of the host magma, must be taken into account when whole-rock geochemical data are interpreted. © 2016 Elsevier B.V.

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