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  • 1
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    Cooling rates of pyroclastic deposits inferred from mineral magnetic investigations: a case study from the Pleistocene Mýtina Maar (Czech Republic) (2020)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2023-06-17
    Description: Tephra layers of the Mýtina Maar, Czech Republic, contain ferrimagnetic Mg–Al-rich titanomagnetite, which is suggested to originate from a fractionated alkaline CO2-rich lithospheric mantle melt. We investigated the magnetic mineralogy and Curie temperature (TC) from tephra deposits of two drill cores (〈 9 m depth). TC calculated (208 ± 14 °C) from chemical composition (Fe2+0.8Mg0.5Fe3+1.1Al0.3Ti0.3O4) is in accordance with TC retrieved from cooling curves of temperature-dependent magnetic susceptibility measurements (195–232 °C). However, thermomagnetic curves are irreversible either with lower (type I) or higher (type II) TC in the heating curve. All curves show transition temperatures above ca. 390 °C, indicating maghemitization. We interpret the irreversibility of TC (∆TC) in terms of different degrees of cation ordering, overprinted or masked by different degrees of maghemitization, which is a low-temperature phenomenon. Negative ∆TC indicates that original deposited titanomagnetite has cooled faster and, therefore, has stored a lower degree of cation ordering compared to heating/cooling rate of 11 °C/min in the Kappabridge. Type II with positive ∆TC indicates higher degree of cation ordering, and, therefore, slower cooling rate. The central part of this deposit shows most severe maghemitization, indicating rather wet emplacement. We, therefore, suggest different eruption styles for deposition of type I pyroclastics with more phreatomagmatic and type II pyroclastics with more phreato-Strombolian eruption styles. Our study is a new approach to discriminate different cooling histories in maar deposits using the Curie temperature of titanomagnetite. We suggest that this method has the potential to discriminate different emplacement modes resulting from different eruption styles.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: CzechGeo/EPOS
    Keywords: ddc:552.2 ; Eger rift system ; Maar-diatreme volcano ; Titanomagnetite ; Curie temperature ; Cation ordering effect ; Maghemitization ; Pyroclastic emplacement mechanism
    Language: English
    Type: doc-type:article
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  • 2
    Electronic Resource
    Electronic Resource
    The Moho Structure in The Western Eger Rift: A Receiver Function Experiment (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 188-194 
    Details
    ISSN: 1573-1626
    Keywords: Eger Rift ; Moho conversions ; receiver function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract We used teleseismic recordings of a temporary deployment of seismic stations and of permanent short period stations in the western Eger Rift system to study the lithosphere with the help of Receiver Functions. The crust-mantle boundary (Moho) is observed at almost all stations by strong P-to-S converted phases. The Moho is basically flat between about 26 – 30 km depth in the entire region. At one station in the Eger Rift (BOH-1, Loket castle) no Moho is observed. We interpret this with the existence of a broad gradient zone there, instead of a sharp discontinuity. This observation, however, needs to be confirmed by more data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022158725170
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  • 3
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    Active Magmatic Underplating in Western Eger Rift, Central Europe (2017)
    Wiley
    In:  EPIC3Tectonics, Wiley, 36, pp. 2846-2862, ISSN: 0278-7407
    Details
    Publication Date: 2018-03-04
    Description: The Eger Rift is an active element of the European Cenozoic Rift System associated with intense Cenozoic intraplate alkaline volcanism and system of sedimentary basins. The intracontinental Cheb Basin at its western part displays geodynamic activity with fluid emanations, persistent seismicity, Cenozoic volcanism, and neotectonic crustal movements at the intersections of major intraplate faults. In this paper, we study detailed geometry of the crust/mantle boundary and its possible origin in the western Eger Rift. We review existing seismic and seismological studies, provide new interpretation of the reflection profile 9HR, and supplement it by new results from local seismicity. We identify significant lateral variations of the high-velocity lower crust and relate them to the distribution and chemical status of mantle-derived fluids and to xenolith studies from corresponding depths. New interpretation based on combined seismic and isotope study points to a local-scale magmatic emplacement at the base of the continental crust within a new rift environment. This concept of magmatic underplating is supported by detecting two types of the lower crust: a high-velocity lower crust with pronounced reflectivity and a high-velocity reflection-free lower crust. The character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events. The lower crust with high reflectivity evidences magmatic underplating west of the Eger Rift of the Late Variscan age. The reflection-free lower crust together with a strong reflector at its top at depths of ~28–30 km forms a magma body indicating magmatic underplating of the late Cenozoic (middle and upper Miocene) to recent. Spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    From mantle roots to surface eruptions: Cenozoic and Mesozoic continental basaltic magmatism (2015)
    SPRINGER
    In:  EPIC3International Journal of Earth Sciences, SPRINGER, ISSN: 1437-3254
    Details
    Publication Date: 2015-11-01
    Description: Basaltic volcanism is an important process in shaping large areas of the Earth’s surface, not only in continental extensional environments and at the ocean floor. This special issue contains a collection of fifteen papers that are dedicated to recent researches on various aspects of continental basaltic magmatism from its mantle roots via the ascent paths of the melt to the surface where different styles of volcanism take place erupting lavas or through explosive volcanism depositing various types of pyroclasts. Two of the fifteen were published earlier (Downes et al. 2015; Herrero-Hernandez et al. 2015). Continental basaltic volcanism also contributes to the total terrestrial sedimentary budget not only by its primary pyroclastic deposits but also their reworked varieties. Most of the papers result from presentations at the BASALT 2013 conference, which took place from April 18–24, 2013, in Görlitz, Germany (Büchner et al. 2013). The conference was organized by the Senckenberg Museum of Natural History Görlitz and co-organized by the International Association of Volcanology and Chemistry of the Earth´s Interior (IAVCEI)—particularly its Commission on Monogenetic Volcanism—and the “Sächsische Landesstiftung Natur und Umwelt” LaNU Academy). Since the conference was held in the heart of Europe in Germany with accompanied field excursions to Poland and the Czech Republic, many contributions are related to the Cenozoic Central European Volcanic Province (Fig. 1). However, there was also a variety of contributions about Mesozoic and Cenozoic basaltic rocks worldwide. This variety is reflected in this issue. The issue brings together studies on different aspects of basaltic magmatism. Thus, this volume contains petrological and geochemical studies spanning from studies of mantle peridotites to those on volcanic rocks as well as papers presenting geophysical data and interdisciplinary interpretation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
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  • 5
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    Helium and carbon isotope signatures of gas exhalations in the westernmost part of the Pannonian Basin (SE Austria/NE Slovenia): Evidence for active lithospheric mantle degassing (2016)
    ELSEVIER SCIENCE BV
    In:  EPIC3Chemical Geology, ELSEVIER SCIENCE BV, 422, pp. 60-70, ISSN: 0009-2541
    Details
    Publication Date: 2016-01-21
    Description: We present new isotope (C, He, Ne, Ar, partly N) and compositional data from the free gas phase of fourteen degassing sites in the westernmost part of the Pannonian Basin near the Austria/Slovenia borderline. Based on these data, the origin of the gases and the degree of modification of the gas signatures due to interaction processes during migration are evaluated. The isotope signatures indicate an origin of helium and CO2 predominantly in the subcontinental mantle. Measured 3He/4He ratios from 4.95 to 6.32 Ra include the highest ones recorded in the whole Pannonian Basin system. Only at three locations in the periphery of the degassing center, a substantial admixture of crustal helium was found. The CO2 in the mofette gases and at the sites with the highest 3He/4He ratios (~ 6.3 Ra) is characterized by δ13C values of − 3.5‰. In comparison with MORB (Mid-ocean Ridge Basalt), it is thus slightly enriched in 13C. The 3He/4He isotope ratios within the range typical for the subcontinental lithospheric mantle (SCLM) point to a fast, localized fluid transport from the magmatic reservoir to the surface. There are only few sites in European non-active volcanic regions where free gases with unmodified SCLM helium isotope signature escape at the surface. A comparison of the elemental and isotopic geochemical characteristics of gases with SCLM-helium signature from four different regions (Massif Central/France, Eifel/Germany, Eger Rift/Czech Republic and the westernmost part of the Pannonian Basin system) indicates that the European SCLM in general is characterized by a reservoir more enriched in 13C compared to MORB.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Provenance and characteristics of rocks from the Yermak Plateau, Arctic Ocean: Petrographic, geochemical and geochronological constraints (2013)
    In:  EPIC3Marine Geology, 343, pp. 125-145, ISSN: 00253227
    Details
    Publication Date: 2017-01-13
    Description: The Yermak Plateau is a prominent bathymetric feature of the Arctic Ocean. To the west it is bordered by the Fram Strait, which forms the only deep-water connection between the Arctic and the other global oceans. Origin, crustal nature and age of the Yermak Plateau are largely unknown. For this study, we investigated dredged rocks of two sites from the Yermak Plateau. Based on petrography, geochemistry, and geochronology, we distinguished between ice-transported and in-situ rocks. Ice-transported material was most likely derived from outcrops of the High Arctic Large Igneous Province (HALIP) on Franz Josef Land, the Siberian trap province, and presumably from northern Svalbard. Our data from the in-situ rocks, in conjunction with previously published geophysical data, show that the investigated parts of the Yermak Plateau are composed of stretched continental crust strongly affected by alkaline magmatism. The continental rocks represent a direct continuation of the exposures on northern Svalbard. Alkaline magmatism took place at ~ 51 Ma and was related to continental rifting in an extensional setting. The melts were formed by low degrees of partial melting of the sub-continental lithospheric mantle and are probably associated with the high-amplitude magnetic anomalies described for the northeastern Yermak Plateau. Extension of the Yermak Plateau was contemporaneous with spreading of the adjacent young Eurasian Basin, and occurred during the peak of compressional deformation affecting North Greenland, Svalbard, and Ellesmere Island. These contrasting regimes were probably compensated by transpression and strike-slip movements along the DeGeer and Wegener Faults. The date of ~ 51 Ma for extension-related magmatism also provides age constraints for the extension-related formation of the Sophia Basin (and thus for water exchange between the Eurasian Basin, the area of the DeGeer Fault and the young Norwegian-Greenland Sea), and for the sediments covering the horst-and-graben structures of the Yermak Plateau.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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