Alpine subduction revisited - new structural and elastic wave velocity models for improved geophysical imaging towards greater depths

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During the Alpine orogeny, both oceanic and continental lithosphere was subducted in a complicated spatial and temporal pattern involving branching ocean basins, microcontinents, and subduction polarity reversal. This resulted in a complex structure of both crust and mantle at depth. Seismic imaging revealed high-velocity anomalies in the upper mantle, apparently dipping SE in the western and central Alps and NE in the eastern Alps. These structures have been interpreted as subducted slabs. Despite elaborate field work throughout the entire Alps and an extensive discussion of several existing seismic transects, many of the structures are still not well understood. Especially the deep structures remain enigmatic in seismic imaging, yet a better understanding is vital to constrain any tectonic model of the Alps. In this project we will study a suite of oceanic and continental rocks from the Western and Central Alps that were deformed under high and ultrahigh pressure conditions during subduction. We will determine their elastic anisotropies on the base of microstructural and textural analysis as well as by laboratory velocity measurements. This data is valuable for the interpretation of seismic imaging and for seismic modelling using the data as input parameters. With such a unique structural and petrophysical database (1) formerly subducted and exhumed oceanic and continental units of the Western and Central Alps can be characterized with respect to their position in paleo-subduction and (2) current seismic velocity anomalies under the Alps may be re-interpreted. Our data can also be instrumental and essential for a large number of projects proposed in the SPP 4D-MB, especially the seismological, the modeling and the tectonometamorphic studies. It fits in the frame of RT1 (Reorg. of Lithosphere), RT3 (Deform. of crust + mantle) and AF-E (GEOLOG. Act.).