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to other elements, hydrogen can diffuse in tourmaline until a closure temperature of about 200–300 °C ( Jibao and Yaquian, 1997 ). The diffusion coefficient for hydrogen in tourmaline is about 10 −14 to 10 −13  m 2 s −1 in the temperature range of

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Central European Geology
Authors:
Elemér Pál-Molnár
,
Luca Kiri
,
Réka Lukács
,
István Dunkl
,
Anikó Batki
,
Máté Szemerédi
,
Enikő Eszter Almási
,
Edina Sogrik
, and
Szabolcs Harangi

nepheline + sodalite of sodalite nepheline syenite reached their closure temperature at 182.4 ± 6.9 and 232.7 ± 8.8 Ma, respectively. K/Ar ages of biotite of granite range from 217.6 ± 8.3 to 206.3 ± 7.8 Ma, whereas the age of alkaline feldspar is 142.7 ± 5

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Abstract

The Mid-Hungarian Zone is a WSW-ENE trending composite structural unit in the basement of the Pannonian Basin that is made up of displaced crustal fragments (terranes) of South Alpine and Dinaridic origin. In the early stage of the Alpine evolution these fragments were located in various sectors of the NW Neotethys region, representing different paleogeographic settings from passive margin through continental slope to oceanic basement. Middle to Late Jurassic closure of the Neotethys led to the development of a suture zone made up of subduction-related complexes that can be followed all along the strike of the Dinarides. During the Cretaceous compressional stages, nappe stacks were formed from the accretionary complex and the fragments of the previously disrupted passive margin. Eastward extrusion (escape) of the ALCAPA Mega-unit during the Oligocene to Early Miocene led to large-scale displacement of fragments of this nappe stack, transporting them to their present-day position, and resulted in dispersal of the northwestern segment of the suture zone. The paper summarizes the basic characteristics of the dislocated blocks, evaluates their relationships and determines their original setting.

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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.

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. 12 359 362 Villa, I.M. 1998: Isotopic closure. - Terra Nova, 10, pp. 42-47. Isotopic closure

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Central European Geology
Authors:
Bassey E. Ephraim
,
Barth N. Ekwueme
,
Mohssen Moazzen
, and
Monir Modjarrad

. Caby K.L.M. Betrand R. Black 1981 Pan African ocean closure and continental collision in the Hoggar

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evolution of the Turan and Scythian platforms: The pre-history of the Palaeo-Tethyan closure. — Tectonophysics, 404 , pp. 175 – 202 . Nikishin , A.M. , M.V. Korotaev , A.V. Ershov , M.F. Brunet 2003

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bezáródási öve (Scissor-like closure belt of the Carpathian Basin) . - MÁFI Évi Jel. 1982-ről, pp. 491 – 500 . Nagymarosy , A. 1989 : Cenozoic formations of North Hungary . - In: Császár , G

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; these were incorporated in the model. The major strike-slip fault in the east is a bounding fault, it provides the closure to the east ( Fig. 8 ). It should be noted that later investigations revealed minor or no role of faults on flow behavior; hence to

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Upon completion, the National Radioactive Waste Repository in Bátaapáti will provide safe storage for low- and medium-level radioactive waste. The emplacement chambers were excavated in a fractured, blocky, granitic rock mass approximately 240 m below surface. One of the tasks related to the repository development is the feasibility demonstration of the permanent repository closure, including long-term rock mass associated issues. The required lifetime exceeds the usual one of an engineering structure. The long-term behavior of the repository needs to be extrapolated from observation over a shorter time period, or from analogous natural caverns. Numerical methods are the most promising techniques to carry out the extrapolation. It is commonly understood that there are significant uncertainties in long-term predictions. Uncertainties can be mitigated by utilizing independent methods to assess long-term behavior and by improving the prediction capability of the calculation model in the short term. The aim of the paper is to: (1) create a numerical model to effectively capture a wide range of the observed behavior of the rock mass, including tunnel-excavation-induced stress change and stress-dependent permeability and (2) identify the possible cause of long-term creep and show that the long-term creep can be captured by the selected calculation method. The moderately fractured rock mass is modeled using the Universal Distinct Element Code, released by Itasca. The joints in the rock mass are explicitly modeled; the blocky nature of the rock mass is captured. The model is verified with actual field observations and monitoring results. Based on the predicted stress state of the rock mass, the potential cause of long-term creep is identified. By fulfilling the two aims explained above, it is concluded that the model can be used to extrapolate in time and serve as a possible estimation method for the long-term behavior of the repository.

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