Abstract
Abstract. The presented study aims to resolve the upper mantle structure around the Trans-European Suture Zone (TESZ), which is the major tectonic boundary in Europe. The data of 183 temporary and permanent seismic stations operated during the period of the PASsive Seismic Experiment (PASSEQ) 2006–2008 within the study area from Germany to Lithuania was used to compile the data set of manually picked 6008 top-quality arrivals of P waves from teleseismic earthquakes. We used the TELINV nonlinear teleseismic tomography algorithm to perform the inversions. As a result, we obtain a model of P wave velocity variations up to about ±3% with respect to the IASP91 velocity model in the upper mantle around the TESZ. The higher velocities to the east of the TESZ correspond to the older East European Craton (EEC), while the lower velocities to the west of the TESZ correspond to younger western Europe. We find that the seismic lithosphere–asthenosphere boundary (LAB) is more distinct beneath the Phanerozoic part of Europe than beneath the Precambrian part. To the west of the TESZ beneath the eastern part of the Bohemian Massif, the Sudetes Mountains and the Eger Rift, the negative anomalies are observed from a depth of at least 70 km, while under the Variscides the average depth of the seismic LAB is about 100 km. We do not observe the seismic LAB beneath the EEC, but beneath Lithuania we find the thickest lithosphere of about 300 km or more. Beneath the TESZ, the asthenosphere is at a depth of 150–180 km, which is an intermediate value between that of the EEC and western Europe. The results imply that the seismic LAB in the northern part of the TESZ is in the shape of a ramp dipping to the northeasterly direction. In the southern part of the TESZ, the LAB is shallower, most probably due to younger tectonic settings. In the northern part of the TESZ we do not recognize any clear contact between Phanerozoic and Proterozoic Europe, but further to the south we may refer to a sharp and steep contact on the eastern edge of the TESZ. Moreover, beneath Lithuania at depths of 120–150 km, we observe the lower velocity area following the boundary of the proposed paleosubduction zone.
Highlights
1.1 Tectonic settingsThe Trans-European Suture Zone (TESZ) is the most fundamental lithospheric boundary in Europe (Pharao, 1999) that marks the transition between the old Proterozoic lithosphere of the East European Craton (EEC) and the younger Phanerozoic lithosphere of central and western Europe (Fig. 1a)
Janutyte et al.: Upper mantle structure around the Trans-European Suture Zone units (Fig. 1b), such as the Belarus–Podlasie Granulite Domain (BPG), the East Lithuanian Domain (EL) and the West Lithuanian Granulite Domain (WLG), which continue in a NE–SW direction into Poland and terminate at the TESZ (Bogdanova et al, 2006)
The aim of this study is to obtain a model of the upper mantle and the seismic lithosphere–asthenosphere boundary (LAB) on a regional scale in the territory around the TESZ (Fig. 1b) using data from the seismic stations operated in the region during the PASSEQ project and the method of teleseismic tomography
Summary
The Trans-European Suture Zone (TESZ) is the most fundamental lithospheric boundary in Europe (Pharao, 1999) that marks the transition between the old Proterozoic lithosphere of the East European Craton (EEC) and the younger Phanerozoic lithosphere of central and western Europe (Fig. 1a). I. Janutyte et al.: Upper mantle structure around the Trans-European Suture Zone units (Fig. 1b), such as the Belarus–Podlasie Granulite Domain (BPG), the East Lithuanian Domain (EL) and the West Lithuanian Granulite Domain (WLG), which continue in a NE–SW direction into Poland and terminate at the TESZ (Bogdanova et al, 2006). The territories in central–western Europe consist of various continental fragments that were subsequently rifted off the northern margin of Gondwana and accreted to the southwestern margin of the Precambrian Baltica during a number of orogenic events (Nolet and Zielhuis, 1994; Pharaoh, 1999; Winchester and the PACE TMR Network Team, 2002; Banka et al, 2002). The developed Tertiary Eger Rift continues 300 km in the ENE–WSW direction and follows the late Variscan mantle transition between the Saxothuringian and the TeplaBarrandian
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