Traces of the crustal units and the upper-mantle structure in the southwestern part of the East European Craton

I Janutyte,M Budraitis,P H Voss,M Majdanski,E Kozlovskaya

doi:10.5194/se-5-821-2014

Abstract

Abstract. The presented study is a part of the passive seismic experiment PASSEQ 2006–2008, which took place around the Trans-European Suture Zone (TESZ) from May 2006 to June 2008. The data set of 4195 manually picked arrivals of teleseismic P waves of 101 earthquakes (EQs) recorded in the seismic stations deployed to the east of the TESZ was inverted using the non-linear teleseismic tomography algorithm TELINV. Two 3-D crustal models were used to estimate the crustal travel time (TT) corrections. As a result, we obtain a model of P-wave velocity variations in the upper mantle beneath the TESZ and the East European Craton (EEC). In the study area beneath the craton, we observe up to 3% higher and beneath the TESZ about 2–3% lower seismic velocities compared to the IASP91 velocity model. We find the seismic lithosphere–asthenosphere boundary (LAB) beneath the TESZ at a depth of about 180 km, while we observe no seismic LAB beneath the EEC. The inversion results obtained with the real and the synthetic data sets indicate a ramp shape of the LAB in the northern TESZ, where we observe values of seismic velocities close to those of the craton down to about 150 km. The lithosphere thickness in the EEC increases going from the TESZ to the NE from about 180 km beneath Poland to 300 km or more beneath Lithuania. Moreover, in western Lithuania we find an indication of an upper-mantle dome. In our results, the crustal units are not well resolved. There are no clear indications of the features in the upper mantle which could be related to the crustal units in the study area. On the other hand, at a depth of 120–150 km we indicate a trace of a boundary of proposed palaeosubduction zone between the East Lithuanian Domain (EL) and the West Lithuanian Granulite Domain (WLG). Also, in our results, we may have identified two anorogenic granitoid plutons.

Highlights

The East European Craton (EEC) (Fig. 1), the palaeocontinent Baltica, has not been tectonically reworked for at least 1.45 Ga (Bogdanova et al, 2006)
The rays experience distortions along their full paths from source to receiver which are mapped in the final results of the inversion, and add up to positive or negative signals; (2) the TELINV code used in this study implements the “flat-earth” transformation which has an effect on the apparent velocities when dealing with large study areas
The model at the bottom is horizontally stretched by about 11 %

Summary

Introduction

The East European Craton (EEC) (Fig. 1), the palaeocontinent Baltica, has not been tectonically reworked for at least 1.45 Ga (Bogdanova et al, 2006). The EEC includes a mosaic of tectonic structures. It has formed during the collision of three palaeocontinents: Sarmatia, Volgo-Uralia and Fennoscandia 2–1.7 Ga (Bogdanova et al, 2001; Artemieva, 2007). The EEC in the east is bordered by the Uralides orogen and the Timan Ridge, and in the west by the TransEuropean Suture Zone (TESZ), the boundary between Proterozoic Eastern Europe and Phanerozoic western-central Europe (Nolet and Zielhuis, 1994). The inner major sutures in the EEC are the Central Russia Rift System and the Pachelma Rift, which mark amalgation of Baltica in the north, Sarmatia in the west and Volgo-Uralia in the east during the Proterozoic Period (Gorbatschev and Bogdanova, 1993). The EEC resulted in a complex structure of the crust and the upper mantle, which were intensively investigated during a number of studies

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Results