Egy összetett kitörési eseménysorozat nyomai a Bükkalján (Észak-Magyarország): a Kács Egység: Signs of complex eruption events at the Bükk Foreland (Northern-Hungary): the Kács Member

A stratified, complex volcanic succession occuring at Kács (Bükk Foreland Volcanic Area, Northern-Hungary) belonging to the Lower Pyroclastic Complex was documented in detail in this work. The tephra-generating volcanic processes were inferred based on the volcanological and granulometric features of the deposits as follows: at least three Plinian eruptions (I-III) produced fallout tephra separated by paleosol horizons recording inter-eruptive quiescence periods. Several features of the earliest eruption sequence suggest a phreatomagmatic eruption style. Regional correlation attempts are supported by paleomagnetic rotation data, which helped the classification of the sequence right below to the Middle Pyroclastic Complex

Egy összetett alsó-miocén piroklasztit sorozat Észak-Magyarországról: az alsó-riolittufa vulkanoszedimentológiája: A complex Lower Miocene pyroclastic succession in Northern Hungary: volcanic sedimentology of the Lower Rhyolite Tuff

The volcaniclastics of the lower rhyolite tuff in the Nógrád Basin (near Nemti) and in the Western Bükk Foreland (near Ostoros) preserve a complex explosive volcanic history. Although the two successions exhibit similar complexity, they are rather different. Hence, a layer-based physical volcanological investigation of the lower rhyolite tuff was required in order to better constrain on its usefulness as a marker horizon and to localize the vents which produced this pyroclastic complex

Tectonic significance of changes in post-subduction Pliocene-Quaternary magmatism in the south east part of the Carpathian-Pannonian Region

The south-eastern part of the Carpathian–Pannonian region records the cessation of convergence between the European platform/Moesia and the Tisza–Dacia microplate. Plio-Quaternary magmatic activity in this area, in close proximity to the ‘Vrancea zone’, shows a shift from normal calc-alkaline to much more diverse compositions (adakite-like calc-alkaline, K-alkalic, mafic Na-alkalic and ultrapotassic), suggesting a significant change in geodynamic processes at approximately 3 Ma. We review the tectonic setting, timing, petrology and geochemistry of the post-collisional volcanism to constrain the role of orogenic building processes such as subduction or collision on melt production and migration. The calc-alkaline volcanism (5.3–3.9 Ma) marks the end of normal subduction-related magmatism along the post-collisional Călimani–Gurghiu–Harghita volcanic chain in front of the European convergent plate margin. At ca. 3 Ma in South Harghita magma compositions changed to adakite-like calc-alkaline and continued until recent times (< 0.03 Ma) interrupted at 1.6–1.2 Ma by generation of Na and K-alkalic magmas, signifying changes in the source and melting mechanism. We attribute the changes in magma composition in front of the Moesian platform to two main geodynamic events: (1) slab-pull and steepening with opening of a tear window (adakite-like calc-alkaline magmas) and (2) renewed contraction associated with deep mantle processes such as slab steepening during post-collisional times (Na and K-alkalic magmas). Contemporaneous post-collisional volcanism at the eastern edge of the Pannonian Basin at 2.6–1.3 Ma was dominated by Na-alkalic and ultrapotassic magmas, suggesting a close relationship with thermal asthenospheric doming and strain partitioning related to the Adriatic indentation. Similar timing, magma chamber processes and volume for K-alkalic (shoshonitic) magmas in the South Apuseni Mountains (1.6 Ma) and South Harghita area at a distance of ca. 200 km imply a regional connection with the inversion tectonics

Post-collisional Tertiary–Quaternary mafic alkalic magmatism in the Carpathian–Pannonian region: a review

Mafic alkalic volcanism was widespread in the Carpathian–Pannonian region (CPR) between 11 and 0.2 Ma. It followed the Miocene continental collision of the Alcapa and Tisia blocks with the European plate, as subduction-related calc-alkaline magmatism was waning. Several groups of mafic alkalic rocks from different regions within the CPR have been distinguished on the basis of ages and/or trace-element compositions. Their trace element and Sr–Nd–Pb isotope systematics are consistent with derivation from complex mantle-source regions, which included both depleted asthenosphere and metasomatized lithosphere. The mixing of DMM-HIMU-EMII mantle components within asthenosphere-derived magmas indicates variable contamination of the shallow asthenosphere and/or thermal boundary layer of the lithosphere by a HIMU-like component prior to and following the introduction of subduction components. Various mantle sources have been identified: Lower lithospheric mantle modified by several ancient asthenospheric enrichments (source A); Young asthenospheric plumes with OIB-like trace element signatures that are either isotopically enriched (source B) or variably depleted (source C); Old upper asthenosphere heterogeneously contaminated by DM-HIMU-EMII-EMI components and slightly influenced by Miocene subduction-related enrichment (source D); Old upper asthenosphere heterogeneously contaminated by DM-HIMU-EMII components and significantly influenced by Miocene subduction-related enrichment (source E). Melt generation was initiated either by: (i) finger-like young asthenospheric plumes rising to and heating up the base of the lithosphere (below the Alcapa block), or (ii) decompressional melting of old asthenosphere upwelling to replace any lower lithosphere or heating and melting former subducted slabs (the Tisia block)

A Miocene Phreatoplinian eruption in the North-Eastern Pannonian Basin, Hungary: The Jató Member

A Middle Miocene, ~8 m thick pyroclastic succession, reported from the Bükk Foreland Volcanic Area (BFVA) in Northern Hungary (Central Europe) specified here as the Jató Member, was produced by silicic phreatomagmatism (Phreatoplinian sensu lato). Two well-preserved outcrops ~8 km apart and inferred to be within ~10–50 km from source represent the discontinuously exposed, layered, paleosol-bounded, phreatomagmatic JatóMember. They show an identical phenocrystal assemblage of feldspar, biotite and amphibole without weathered zones or signs of erosion, that suggest deposition in one eruption phase lasting hours to months. The succession contains three subunits: 1) subunit A, 1.8 m thick, a series of well-sorted fine to coarse ash or lapilli tuff layers with constant thickness; 2) subunit B, 2.1 m thick, a series of normal-graded layers with an upper fine-grained zone containing abundant ash aggregates with a coarser-grained core and distinctively finer-grained outer rim; 3) subunit C, 4.5 m thick, a massive, poorly to well-sorted coarse ash with gas escape structures and ash aggregates at its base. The upward change of these lithofacies implies an initially sustained dry fallout-dominated deposition of ash and pumice lapilli resulting in subunit A. Subsequently, multiple wet and dilute Pyroclastic Density Currents (PDCs) dispersed subunits B and C. The general abundance of PDC-related ash aggregates in the middle-upper part of the succession (particularly in subunit B), and the transformation of a fall-dominated to a collapsing depositional regime producing wet dilute PDCs, imply the increasing influence of water during the eruption (Phreatoplinian sensu lato). The presence of water is related to an epicontinental sea duringMiddle to LateMiocene in the Carpatho-Pannonian region. The transition from an initial dry magmatic phase generated fallout activity followed by the emplacement of wet PDCs' rich in ash aggregates, when external water infiltrated from a surrounding lake or sea water entered the vent.ÚNKP-16-3 New National Excellence Program of the Ministry of Human Capacities and the National Talent Program – Young Talents of the Nation (NTPNFTÖ- 18-B-0130). Thisworkwas supported by theHungarian Scientific Research Fund project nos. K105245, K115472, K128625, K131894, K128122 and by the European Union and the State of Hungary, cofinanced by the European Regional Development Fund in the project of GINOP - 2.3.2 - 15 - 2016 - 00009 ICER. KN's contribution and field work were possible by the fund available under the Erasmus+ International Credit Mobility, - ELTE –Massey University Research Cooperation Program. Balázs Bradák acknowledges the financial support of project BU235P18 (Junta de Castilla y León, Spain) and the European Regional Development Fund (ERD)

Volcanic Landforms and Landscapes of the East Carpathians (Romania) and Their Geoheritage Values

The Neogene&ndash;Quaternary volcanic range running along the East Carpathians in Romania, extends from the Oa&#537; Mountains, in the north-west, to the South Harghita Mountains and the Per&#537;ani Mountains, in the south-east, as part of the broader volcanic province of the Carpathian&ndash;Pannonian Region. It resulted from intense volcanic activity during the 15&ndash;0.1 Ma time interval, generating huge volumes of effusive and explosive products and a variety of volcanic edifices and primary landforms from large composite volcanoes to small-sized domes/dome-coul&eacute;es/lava flows and volcaniclastic plateaus around them. The present-day landforms were shaped by various syn-volcanic deformation processes (such as volcano spreading), post-volcanic erosion of various degrees and types (including glacial erosion on the highest-elevation parts and relief inversion in the peripheral areas) and modern anthropic intervention. Developed on this diverse volcanic substrate, the present-day landscape shows a large variety of aspects due to further factors (original topography, elevation, vegetation cover, distance from settlements, anthropic activities, and degradation processes). This volcanic range hosts many geoheritage-relevant sites of various spatial extent (from hundreds of km2 to limited areas of a few 10 m2) and of protection status (from national parks, natural or scientific reserves, natural monuments, and protected areas to areas with no protection at all). Despite its high geoheritage potential, geoparks are still absent, geotrails are sparse, and geotourism is in its infancy in the East Carpathian volcanic range