4:15pm - 4:30pm
Pre-Variscan (Lower Devonian) deformation of the Silurian magmatic arc of the East Odenwald (Mid-German Crystalline Zone, Variscides)
1Technische Universität Darmstadt, Germany; 2Goethe University Frankfurt, Germany
The Böllstein Odenwald is forming a large anticline of mainly pre-Devonian rock in the Mid-German Crystalline Zone (MCGZ). The contact between core and schist envelope of the anticline is well exposed at Weichberg quarry. Metasedimentary rocks of the schist envelope are intruded by granodioritic sills of a Silurian magmatic arc, showing at least two folding phases: Recumbent tight isoclinal folds are overprinted by upright gentle folds. A pegmatite dike, intruding at 411 ±2 Ma (U-Pb analyses on zircon) into the schist envelope rocks, crosscuts perpendicular to the main foliation. It shows only a weak schistosity related to the isoclinal folding, which therefore must have been active in Lower Devonian (>411 ±2 Ma; Lochkovian/Pragian) after the Silurian intrusion of the granodiorite sills (U-Pb on zircon ca. 423 Ma, Dörr et al. in press). The Lower Devonian deformation of the East Odenwald probably results from the collision of the MGCZ with the NW boundary of the Saxothuringian Zone.
The core is represented by a (meta)granite intruding into the schist envelope at 404 ±2 Ma (U-Pb method on zircon). A deformed fold directly at the contact between metagranite and metasediments and dikes terminated at the contact point to eastward directed tectonic movements between core and schist envelope after 404 ±2 Ma, probably at 375 Ma (U-Pb on zircon, Todt et al. 1995). These results are compared to other units occupying a similar position in the European Variscides and help to clarify the position of the East Odenwald during Variscan orogeny.
4:30pm - 4:45pm
Imaging the warm lithospheric mantle in the Mediterranean-Alpine region: integrated thermochemical inversion of surface wave dispersion, heat flow and elevation data.
1Universidad Complutense de Madrid, Madrid, Spain; 2School of Cosmic Physics, Geophysics Section, Dublin Institute for Advanced Studies, Dublin, Ireland; 3Institute of Geosciences, Christian‐Albrechts‐Universität, Kiel, Germany; 4National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, Egypt; 5GEOMAR, Kiel, Germany
Here we investigate the thermal structure of the lithosphere in the Alpine-Mediterranean region. We focus on areas characterized by negative velocity anomalies according to a lithosphere-upper mantle surface-wave tomography study (El-Sharkawy et al., 2020) to analyze possible lithospheric thinning and melting. Surface-wave, phase-velocity curves were determined by interstation cross-correlation measurements and inverted for a set of phase-velocity maps, spanning a broad period range. We invert fundamental mode Rayleigh and Love dispersion curves together with surface elevation and heat flow for the 1D thermochemical lithospheric structure in 13 columns. The inversion is framed within an integrated geophysical-petrological setting where mantle seismic velocities and densities are computed thermodynamically as a function of the in situ temperature and compositional conditions (Fullea et al., 2021). We analyze the presence of small amounts of melt in the vicinity of the lithosphere-asthenosphere boundary. We conduct sensitivity tests to asses the uncertainties associated with alternative experimental results accounting for the effect of melt and water on seismic velocities. Our results show that the lithosphere is thin (60-90 km) over the whole negative velocity anomaly area in the Alpine-Mediterranean region. We find the thinnest lithosphere in the Pannonian and Tyrrhenian basins (60-70 km), while the thickest lithosphere is located in the Iberia and Central Europe (80-90 km). Our thermal models show the presence of melting near the LAB (1300 ºC isotherm) in some of the columns (e.g. Pannonian and Tyrrhenian basins) associated with a pronounced drop in Vs velocities.
4:45pm - 5:00pm
Revisiting GNSS vertical velocity in the Eifel volcanic field
Institute of Geodesy and Geoinformation, University of Bonn, Germany
Recent evidence suggests that the Eifel Volcanic Fields (EVF) make measurable contributions to the surface deformation in GPS networks, but quantitative assessments of displacement time series and their impacts on long-term rates are lacking. The GPS sites in the EVF indicate anomalously slow uplift (up to 1 mm/yr) which stays at the limit of GPS sensitivity and noise level for monitoring crustal deformation in geophysical applications. Since the primary aim of existing geodetic GNSS networks in west Germany is positioning service for land survey engineering and transportation applications, many sites have been installed on inexpensive and non-geodetic monuments, thus highly vulnerable to disturbances resulting from monument instability and near-field multipath sources. These potential pitfalls have not been fully addressed in previous studies. Here, we reprocess all available GNSS observations (combined GPS and GLONASS observations) using precise point positioning technique and present precise analysis of displacement time series to generate reliable long-term rates and uncertainties. Individual time series is examined to determine local motion, non-linear deformation due to regional and local hydrology and site-specific noise.
5:00pm - 5:15pm
Numerical Modeling of the 2007-2009 Lava Dome Growth in the Crater of Volcán de Colima, México
KIT university, Germany
Volcán de Colima is active andesitic stratovolcano in México located at the height of about 3860 m above sea level. It belongs to the Colima Volcanic complex within the Trans-Mexican Volcanic Belt. This volcano is characterized by intermittency of explosive and effusive episodes of volcanic eruptions. For 2007-2009 slowly extruded magma led to a lava dome formation and growth in the volcanic crater. In this work, we present two-dimensional numerical models of the lava dome growth, which have been computed on the KIT SCC bwunicluster using the Ansys Fluent software. The aim of the numerical study is to understand the link between the rheological properties of the lava dome and the morphological shapes of the dome. Numerical models of lava dome growth incorporate the crystal growth kinetics and the realistic topography of the crater floor. We consider several scenarios of dome growth with different conduit shape, initial and equilibrium crystal contents to analyze the model parameters controlling the morphology of the growing dome. The extrusion rate, the characteristic time of crystal content growth in lava, and the characteristic lava viscosity have been used as tuning parameters to optimize the difference between the morphological shapes of the observed and modeled domes. The numerical results show a good agreement with observations and allow constraining the viscosity of lava dome.