Description: The increasingly dense coverage of Europe with permanent and temporary broadband seismic stations makes it possible to image its lithosphere and asthenosphere structure in great detail, provided that structural information can be extracted effectively from the very large volumes of data. In a new implementation of the classical two-station method, Rayleigh and Love dispersion curves are determined by cross-correlation of seismograms from a pair of stations. Between 5 and 3000 single-event dispersion measurements are averaged per inter-station path in order to obtain robust, broad-band dispersion curves with error estimates. In total, around 63000 Rayleigh- and 27500 Love-wave dispersion curves between 10 s and 350 s have been determined, with standard deviations lower than 2 % and standard errors lower than 0.5 %. Using our large new dataset, we construct phase-velocity maps for central and northern Europe. According to checkerboard tests, the lateral resolution in central Europe is ≤ 150 km. The new, broad-band, phase-velocity dataset offers abundant, valuable information on the structure of the crust and upper mantle beneath Europe. In our contribution we present and discuss results, which shed new light on the lithosphere-asthenosphere structure across the Transeuropean Suture Zone spanning from the Variscan European Platform towards the Proterozoic East European Platform. Comparison of regional surface-wave tomography with independent data on sediment thickness in North-German Basin and Polish Trough (from a compilation of deep seismic sounding results) confirms the accuracy of the imaging using our short-period, phase-velocity measurements. The region of the Tornquist- Teisseyre Zone is associated with a stronger lateral contrast in the lithospheric thickness from the East European Platform towards the southwest compared to the region across the Sorgenfrei-Tornquist Zone as can be clearly seen from the longer periods.

Description: According to classical plume theory, the Tristan da Cunha plume is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. However, Tristan da Cunha is enigmatic as it cannot be clearly identified as a deep-rooted hot spot, but may instead be related to a more shallow feature in the mantle that could actually have been caused by the opening of the South Atlantic. The equivocal character of Tristan da Cunha is largely due to a lack of geophysical and petrological data in this region. We therefore staged a multi-disciplinary geophysical study of the region by acquiring passive marine electromagnetic and seismic data, and bathymetric data within the framework of the SPP1375 South Atlantic Margin Processes and Links with onshore Evolution (SAMPLE) funded by the German Science foundation. The experiment included two expeditions onboard the German R/V MARIA S. MERIAN in 2012 and 2013. In addition to the geophysical work, a landing party collected samples for petrological studies. In our contribution we present first results on the shallow lithosphere structure beneath the Tristan da Cunha archipelago derived from geophysical studies. These results are combined with results from thermobarometric analyses of basanitic/ankaramitic rocks that represent the main rock type on the island. The more evolved products of the eruption in 1962, (trachyandesites), were also studied to include the full range of magma compositions. Clinopyroxene-melt thermobarometry yielded crystallization pressures between 4 and 14 kbar, corresponding to depths of 12-42 km, whereby the youngest and most evolved rocks erupted from the shallowest depth. Olivine-, clinopyroxene-, and plagioclase-melt thermometry yielded magmatic temperatures of 1100° - 1320°C. The Moho below the archipelago is at approximately 11-12 km depth based on the receiver function method at two island stations and ocean-bottom seismometers. Therefore the petrologic depth estimates demonstrate that magmas erupted from a plumbing system in the uppermost mantle.