Neogén mészalkáli vulkanizmus és hidrotermális tevékenység tér-időbeli rekonstrukciója a Nyugati- és Keleti-Kárpátok átmeneti zónájában = Evolution of the Neogene calc-alkaline magmatic and hydrothermal activity in the central part of the Carpathian Arc

Kutatásaink fő területei a Tokaji hegység, továbbá Szlovákiában a Szalánci és a Vihorlát hegységek voltak. Eredményeinket a szlovákiai kollégákkal történő együttműködéseinken kívül az Okayamai Egyetem (Japán) K-Ar laboratóriumával, a Freibergi Egyetem vulkanológusaival és a Zágrábi egyetem munkatársaival kialakított kapcsolatok segítségével értük el. A Tokaji hegységben a Szerencsi dombság, a pálházai perlitvonulat, a füzérradványi illitelőfordulás specifikumait (a hidrotermális és vulkáni folyamatok kapcsolatát, a magmás tevékenység vulkanológiai jellemzőit), továbbá a riolitos vulkanizmus tér-időbeli lefolyását és geokémiai jellegeit vizsgáltuk. Megállapítottuk a pálházai perlit 13.5 millió éves, a füzérradványi illit 11.89 millió éves korát. A Szerencsi dombság hidrotermális zónái 11 millió év körüli nagyméretű hidrotermás rendszer részeiként értelmezhetők, de e zónák jelentős vertikális tektonikai átmozgatás révén kerültek a mai helyzetükbe. A riolitos vulkanimus radiometrikus koradatai és geokémiai jellegei között összefüggést mutattunk ki. A Szalánci hegység fő vulkáni kitörései 10.8 és 13.5 millió év között mentek végbe, ezen belül a hidrotermális események fő időszaka 11.4 millió évesnek bizonyult. Fluidzárvány vizsgálatokkal meghatároztuk az egyik fő kitörési centrum lepusztulási mélységét (700-800m) amely jóval meghaladja a Tokaji hegység általános eróziós szintjét (0-500m). A Vihorlát-hegység mészalkáli vulkanizmusára 9.2-12.6 millió éves kort határoztunk meg. | The major areas of our research were the Tokaj Mts., as well as The Slanské and Vihorlat Mts. in Slovakia. Our results have been achieved by international cooperations (Okayama University, Freiberg University, Zagreb University, Geological Survey of Slovakia). We have studied spatial-temporal evolution and geochemical characteristics of the rhyolite volcanism, as well as specifications (reletionships of volcanism and hydrothermal activity, volcanological features) of the Szerencs Hills area, the perlite field at Pálháza and illite dposit at Füzérradvány. We determined the 13.5 Ma age of perlite (Pálháza) and 11.89 Ma age of illite (Füzérradvány). The hydrothermal zones of the Szerencs Hills are parts of a large scale hydrothermal field developped at about 11 Ma, but the various parts were emplaced into their recent positions by significant vertical movements. We have shown correlation between the radiometric ages and geochemical characteristics of rhyolite volcanism. The major volcanic eruptions of the Slanské Mts. have taken place between 10.8 and 13.5 Ma and the characteristic period of hydrothermalism was at around 11.4 Ma. On the basis of fluid inclusions studies we have determined the erosion depth of one of the eruption centre (700-800m) which is much deeper than the general erosion level in the Tokaj Mts. (0-500m). The calc-alkaline volcanism in the Vihorlat Mts. occured between 9.2 and 12.6 Ma

Dome-building volcanic activity in the Oas-Gutai Neogene Volcanic Area, Eastern Carpathians, Romania

A complex dome-building volcanic activity developed during a 5 Myr time interval (13.2- 8.0 Ma) in Oaş-Gutâi Mts., associated to the intermediate volcanism of the Oaş-Gutâi Neogene volcanic area (OG). Numerous domes were built up in the entire volcanic region also triggering both non-explosive and explosive fragmentation volcanic processes. The volcanic forms consist of extrusive domes, lava domes and dome- flows/coulées and cryptodomes predominantly as solitary domes, or compound domes and dome complexes. The domes are comprised of andesites, dacites and rhyolites (acid andesites and dacites are prevalent). The volcanic rocks show a calc- alkaline and medium to high-K character and typical subduction-zone geochemical signatures. Overall, either subaerial or subaqueous, the dome growth and collapse associated with fragmental explosive or non-explosive processes, was dominantly responsible for most of the volcanic products. Dome emplacement in submarine setting is commonly associated with marginal auto- brecciation, much subordinated explosive events and subsequent resedimentation. Overall, the dome-building volcanic activity in OG is recorded to a monogenetic-type of volcanism. The series of dome-building events which were triggered and controlled by magma-mixing and -mingling processes developed from time to time in different locations of O

The Rudnik Mts. volcano-intrusive complex (central Serbia): An example of how magmatism controls metallogeny

This study reports and discusses new radiometric ages, petrographical and volcanological observations and whole rock geochemical data of the rocks of the Rudnik Mts. volcano-intrusive complex. The complex hosts a Pb-Zn-Ag deposit and belongs to the Serbo-Macedonian metallogenetic belt. Two distinct igneous events are distignuished. The first occurred >30 Ma and was mainly characterized by extrusive and shallow intrusive dacites and andesites and was unrelated to mineralization. The second igneous event occurred <23 Ma and was highly heterogeneous in terms of volcanic products and petrographic varieties, but with predominance of quartzlatites. The dacite-andesites (first event) and the quartzlatites (second event) are geochemically similar and display a calc-alkaline affinity and highly incompatible element enriched patterns on spider diagrams, but the younger quartzlatites are richer in K2O, Rb and Ba and poorer in Sr. This is taken as evidence that mixing between an ultrapotassic lamprophyre/lamproite magma and an acid calc-alkaline (dacite-like) magma was essential petrogenetic processes during the second event. The proposed simplified volcanological model suggests that this mixing was responsible for triggering strongly explosive volcanic activity as well as for providing conditions for active hydrothermal and mineralization processes. The observed link between a specific magmatic phase and ore deposit formation can be a general phennomenon in the Balkans, and must be addressed by further and more advanced studies

Geochemistry of Sarmatian volcanic rocks in the Tokaj Mts (NE Hungary) and their relationship to hydrothermal mineralization

Abstract In the Tokaj Mts (NE Hungary), which is a part of the Inner Carpathian Volcanic Arc, large amounts of intermediate-acidic calc-alkaline volcanic rocks accumulated in a N-S oriented graben-like structure during the Badenian-Sarmatian-Pannonian period, in relation with the closure of the Alpine Tethys (Penninic) ocean. Although previous research on volcanism and related hydrothermal processes produced a huge number of K/Ar age data no systematic petrochemical database has been available up to now from the Tokaj Mts. In this study we publish new results of geochemical analyses completed on systematically collected basaltic, andesitic, dacitic and rhyolitic rocks, and of the spatialtemporal evaluation of petrochemical signatures, with special reference to origin of magmatism and relationships of rhyolite to hydrothermal mineralization. In the southern Tokaj Mts rhyolite contains K-feldspar phenocrysts, while this phenomenon is absent in the rhyolite from the northern areas of the mountains. In accordance with this, significant potassium enrichment occurs in the south (whole rock K2O content varies between 4.35 and 5.61 wt%), whereas rhyolite from the northern Tokaj Mts is less enriched in potassium (K2O content is from 3.28 to 5.1 wt%). The most significant difference between the northern and southern dacite is the age of their formation. They were formed at the same time as rhyolite and andesite (between 13.4 and 11 Ma) in the northern Tokaj Mts, while they are much younger (10.57–10.1 Ma) in the southern Tokaj Mts, where they post-date hydrothermal activity. The boron content (10.1–52.12 µg/g) and the patterns of other trace elements of the volcanic rocks show typical subduction-related features; however, direct influx of subduction-related fluids during magma generation can be excluded. A more plausible explanation for the magma genesis is decompression melting of a previously metasomatized mantle, enriched with subduction-related components. Additionally, the unmineralized northern rhyolite samples contain much less Cl (usually below 0.2 wt%) than the high-K rhyolite in the southern part of the Tokaj Mts (usually more than 0.2 wt%), which correlates with the presence/absence of spatially and temporally related epithermal mineralization in these areas

Geocronología preliminar K/Ar del Campo Volcánico del Basalto Cráter, Patagonia Septentrional

El campo volcánico del Basalto Cráter (CVBC) constituye uno de los campos basálticos cuaternarios de intraplaca de la Patagonia septentrional. El estudio sistemático de la geología, volcanología y geocronología del CVBC muestra una historia eruptiva "multiepisódica" de volcanes basálticos. Las dataciones K-Ar realizadas sobre roca total son coherentes con el control estratigráfico. Las edades obtenidas para el Basalto Cráter permiten distinguir tres episodios diferentes, pero individualmente coherentes, de actividad volcánica, ocurridos hace ~1,0 Ma; 0,6 Ma y 0,3 Ma. Las diferencias de edad parecen ser significativas, aún cuando el contenido de argón radiogénico determinado en los análisis de roca total resultó menor al 10 %.The Crater Basalt volcanic field is one of the Quaternary intraplate basaltic fields in northern Patagonia. A systematic geological, volcanological and geochronological study of CBVF indicates a "multistage history" of eruptions of basaltic volcanoes. K/Ar dating, using whole rock samples shows that the measured analytical ages are fully consistent with the available stratigraphic control. The radiometric ages fall into three distinct, internally consistent age groups, which give evidence that there were at least three major episodes of volcanic activity, at about 1.0 Ma, 0.6 Ma and 0.3 Ma ago. The age differences appear to be just significant, even although less than 10 % radiogenic argon was found in the isotope analysis of whole rock samples.Fil: Pécskay, Zoltán. Hungarian Academy of Sciences. Institute of Nuclear Research; HungríaFil: Haller, Miguel Jorge F.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Németh, Karoly. Massey University; Nueva Zelanda. Geological Institute of Hungary; Hungrí

Time-space evolution and volcanological features of the Late Miocene-Quaternary Calimani-Gurghiu-Harghita Volcanic Range, East Carpathians, Romania. A Review.

The Carpathian-Pannonian Region (CPR) hosts one of the major Cainozoic volcanic provinces of Europe extending in space over 6 eastern European countries.The lithospheric evolution of this large area governed by large-scale asthenospheric processes is recorded by products of volcanic activity occurred during a time interval of more than 21 million years. According to their surface occurrence areas, ages and composition the Neogene volcanics of CPR were systematized in three main groups: 1) mostly explosive products of felsic magmas generated at the beginning of volcanism in the whole CPR and in their particular occurrence areas (21-12 Ma) developed in the actual intra-Carpathian Pannonian Basin, 2) mostly intermediate calc-alkaline rocks emplaced in both the intra-Carpathian areas and along the arcuate Carpathian fold-and-thrust belt, and 3) Na- and K- alkaline and ultra-alkaline products clustered in a number of monogenetic volcanic fields across the whole intra-Carpathian realm developed in the final stages of volcanic activity of the CPR as a whole and of their particular occurrence areas. The ca. 160 km long Călimani-Gurghiu-Harghita volcanic range (CGH) developed as part of the intermediate calc-alkaline volcanism closely related in space with the fold-and-thrust belt of the Carpathians, representing the south-eastern segment of the CPR. Although its map view and general petrochemical and volcanological characteristics are quite similar with those of other segments of the orogene belt- tied calc-alkaline volcanic segments, at a closer look CGH displays a number of unique features. The time-space evolution of CGH is particular not only in that it is the youngest (10.5 to < 0.05 Ma) dominantly calc-alkaline segment in CPR but also it shows a transient character. Unlike other segments along which volcanism occurred simultaneously forming true subduction-related 400 to 800 km long volcanic fronts which were stable in time for millions of year, in CGH volcanic activity migrated continuously along the range from NW to SE. So, during any given 1 Ma time interval active volcanism was restricted to very limited areas and to just a few active volcanic centers. The along-range shift of volcanic foci was concurrent with progressively lower volumes of magma erupted and decreasing magma output rates. As a result, gradually lower-volume and less complex volcanic edifices were built up. Moreover, at the range-ending and youngest South Harghita sub-segment, magma compositions gradually changed from normal calc-alkaline to high-K calc-alkaline and shoshonitic, and adakitic features emerged at the end of volcanic activity, after a time gap of 0.5 Ma. This marks a major geodynamic event in the development of the East Carpathians themselves. During the transient volcanism of CGH, edifices of varying volume and complexity were built up forming a row of tightly- packed adjoining stratovolcanoes/composite volcanoes whose peripheral volcaniclastic aprons complexly juxtaposed, overlapped and merged with each other. The largest ones (Călimani caldera, and Fâncel-Lăpuşna) developed until caldera stage. Some of them (Rusca-Tihu in the Călimani Mts., Vârghiş in the North Harghita Mts.) became unstable during their growth and collapsed, generating widespread large-volume debris avalanche deposits. Edifice instability was solved by volcano-basement interaction processes, such as volcano spreading, at some large-volume volcanoes (in particular those in the Gurghiu Mts.). Volcano typology changed at the smaller-volume constructs toward the southeastern terminus of the range in the South Harghita Mts. from typical large stratovolcanoes to smaller composite volcanoes, dome clusters and isolated domes and simpler internal structures. As a whole, CGH displays an extremely particular evolutionary pattern strongly suggesting a transient character and decreasing to extinguishing volcanic activity along its length from NW to SE