Seismic anisotropy beneath the western part of the Carpathian-Pannonianregion inferred from combined SKS splitting and mantle xenolith studies

Nóra Liptai,László Aradi,Gyöngyvér Szanyi,Csaba Szabó,Bálint Süle,István Kovács,Máté Timkó,Sierd Cloetingh,Gábor Timár,György Falus,Götz Bokelmann,Zoltán Gráczer

doi:10.5194/egusphere-egu22-13364

Abstract

&lt;p&gt;Information on mantle anisotropy can be obtained from methods such as&lt;br&gt;studying the lattice-preferred orientation (LPO) in mantle peridotites,&lt;br&gt;or conducting shear-wave splitting (SKS) analyses which allow to&lt;br&gt;determine whether it is a single or multi-layered anisotropy and the&lt;br&gt;delay time of the fast and slow polarized wave can indicate the&lt;br&gt;thickness. In this study we provide a detailed SKS mapping on the&lt;br&gt;western part of the Carpathian-Pannonian region (CPR) using an increased&lt;br&gt;amount of splitting data, and compare the results with seismic&lt;br&gt;properties reported from mantle xenoliths to characterize the depth,&lt;br&gt;thickness, and regional differences of the anisotropic layer in the&lt;br&gt;mantle.&lt;br&gt;According to the combined SKS and xenolith data, mantle anisotropy is&lt;br&gt;different in the northern and the central/southern part of the western&lt;br&gt;CPR. In the northern part, the lack of azimuthal dependence of the fast&lt;br&gt;split S-wave indicates a single anisotropic layer, which agrees with&lt;br&gt;xenolith data from the N&amp;#243;gr&amp;#225;d-G&amp;#246;m&amp;#246;r volcanic field. In the central&lt;br&gt;areas, multiple anisotropic layers are suggested by systematic azimuthal&lt;br&gt;variations in several stations, which may be explained by two,&lt;br&gt;petrographically and LPO-wise different xenolith subgroups described in&lt;br&gt;the Bakony-Balaton Highland. The shallower layer is suggested to have a&lt;br&gt;&amp;#8216;fossilized&amp;#8217; lithospheric structure, which could account for the&lt;br&gt;occasionally detected E-W fast S-orientations, whereas the deeper one&lt;br&gt;reflects structures responsible for the regional NW-SE orientations&lt;br&gt;attributed to the present-day convergent tectonics. In the Styrian&lt;br&gt;Basin, results are ambiguous as SKS splitting data hints at the presence&lt;br&gt;of multiple anisotropic layers, however, it is not supported clearly by&lt;br&gt;xenolith data.&lt;br&gt;Spatial coherency analysis of the splitting parameters put the center of&lt;br&gt;the anisotropic layer at ~140-150 km depth under the Western&lt;br&gt;Carpathians, which implies a total thickness of ~220-240 km. Thickness&lt;br&gt;calculated from seismic properties of the xenoliths resulted in lower&lt;br&gt;values on average, which may be explained by heterogeneous sampling by&lt;br&gt;xenoliths, or the different orientation of the mineral deformation&lt;br&gt;structures (foliation and lineation).&lt;/p&gt;

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