Two subduction-related heterogeneities beneath the Eastern Alps and the Bohemian Massif imaged by high-resolution P-wave tomography

We present high-resolution tomographic images of the upper mantle beneath the Eastern Alps and the adjacent Bohemian Massif (BM) in the north based on recordings from the AlpArray-EASI and AlpArray seismic networks. The tomography locates the Alpine high-velocity perturbations between the Periadriatic Lineament and the Northern Alpine Front. The northward-dipping lithosphere is imaged down to ∼ 200–250 km of depth, without signs of delamination. The small amount of crustal shortening compared to that in the Western Alps and the bimodal character of the positive perturbations with a separation beneath the Tauern Window indicate a dual source of the velocity heterogeneity, most probably formed by a mixture of a fragment of detached European plate and the Adriatic plate subductions. A detached high-velocity heterogeneity, sub-parallel to and distinct from the Eastern Alps heterogeneity, is imaged at ∼ 100–200 km beneath the southern part of the BM. We associate this anomaly with the western end of a SW–NE-striking heterogeneity beneath the south-eastern part of the BM, imaged in models of larger extent. The strike, parallel with the Moldanubian–Brunovistulian mantle–lithosphere boundary in the BM and with the westernmost part of the Carpathian front, leads us to consider potential scenarios relating the heterogeneity to (1) a remnant of the delaminated European plate, (2) a piece of continental-and-oceanic lithosphere mixture related to the building of the BM, particularly to the closure of the old Rheic ocean during the MD–BV collision, or (3) a lithospheric fragment going through to the NW between the Eastern Alps and Western Carpathians fronts in a preceding subduction phase. The study is dedicated to our outstanding and respected colleague Vladislav Babuška, who coined innovative views on the European lithosphere and died on 30 March 2021

Západní část Oháreckého riftu – vliv plášťových hranic paleodesek na povrchovou tektoniku

Boundaries of blocks of the mantle lithosphere, with a fabric modelled from seismic anisotropy, predestined locations of the Eger Rift, Cheb Basin, Quaternary volcanoes, crustal earthquake swarms and exhalation centers of CO2 and 3He of mantle origin

Novel anisotropic teleseismic body-wave tomography code AniTomo to illuminate heterogeneous anisotropic upper mantle: Part II - Application to data of passive seismic experiment LAPNET in northern Fennoscandia

Seismic anisotropy provides a unique constraint on the past and present dynamics of the lithosphere and sublithospheric mantle. To contribute to studies of large-scale tectonic fabric, we have developed code AniTomo for regional anisotropic tomography. AniTomo allows us to invert simultaneously relative traveltime residuals of teleseismic P waves for 3-D distribution of isotropic-velocity perturbations and velocity anisotropy in the upper mantle. Weak hexagonal anisotropy with the symmetry axis oriented generally in 3-D is considered. The first application of novel code AniTomo to data from passive seismic experiment LAPNET results in a model of anisotropic velocities of the upper mantle beneath northern Fennoscandia. We have opted for northern Fennoscandia for the first application because it is a tectonically stable Precambrian region with a thick anisotropic mantle lithosphere without significant thermal heterogeneities. We carefully analyse the distribution of the rays to limit the fully anisotropic inversion only to the volume with the sufficient directional ray coverage. Capability of the given inversion setup to reveal large-scale anisotropic structures in the upper mantle is documented by a series of synthetic tests. The strongest anisotropy and the largest velocity perturbations concentrate at depths corresponding to the mantle lithosphere, while in deeper parts of the tomographic model, the lateral variations are insignificant. We delimit regions of laterally and vertically consistent anisotropy in the mantle–lithospheric part of the model. We attribute the retrieved domain-like anisotropic structure of the mantle lithosphere in northern Fennoscandia to preserved fossil fabrics of the Archean microplates, accreted during the Precambrian orogenic processes.ISSN:0956-540XISSN:1365-246

Cenozoic volcanism in the Bohemian Massif in the context of P‐ and S‐velocity high‐resolution teleseismic tomography of the upper mantle

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