Klébesz, Rita

Kovács, István

Liptai, Nóra

Patkó, Levente

Pintér, Zsanett

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II6hLHERZOLITEfrom 4 to 15 may 2014OROGENIC LHERZOLITE CONFERENCEMarrakechMOROCCOfrom 4 to 15 may 2014OROGENIC LHERZOLITE CONFERENCEMarrakechMOROCCO_ ~J:l!-~onference field trip to -.!he Beni Bousera Q!'~genic P~ridotite ,_____ _ _ _.__- Conference ~eeting i~ Mar~kec~ lH6tel Le Semi_r_am_~_'s_) ___ ~-conf~~~e_field_ trip to the Middle Atlas Volcanics and Mantle Xe_n_o_l_i_th_s __________ ~~ Post-conference fie~ trip to the Anti-Atlas Pan-African OphioitesPetrophysical and seismological model of the lithospheric mantlebeneath the N 6grad-Gomor Volcanic Field (N orthern PannonianBasin)Rita Klebesz1, N6ra Liptai2, Istvan Kovacs3, Levente Patk62, Zsanett Pinter4, Gyorgy Falus3,Zoltan Graczer5, Gyongyver Szanyi5, ViktorWesztergom1; Csaba Szab62(1) MT A CSFK Geodetic and Geophysical Institute; Sopron, Hungary(2) Lithosphere Fluid Research Lab, Institute of Geography and Eanh Sciences, Eotvos University,Budapest, Hungary(3) Geological and Geophysical Institute of Hungary; Budapest, Hungary(4) Bayerisches Geoinstitut, University of Bayreuth; Bayreuth, Germany(5) MTA CSFK GGL Kovesligethy Rad6 Seismological Observatory; Budapest, HungaryN6grad-Gomor Volcanic Field (NGVF) is one of the five known occurrences in the CarpathianPannonian region (CPR) where Plio-Pleistocene alkali basalts have sampled the upper mantle,bringing upper mantle xenoliths to the surface. NGVF is located in the northern part of thePannonian Basin.For this study, 15 lherzolite and 2 wehrlite xenoliths were selected from the central and southernparts of the NGVF. These xenoliths represent a small volume (~4000 km3) of the upper mantlefrom a depth of about 35-50 km. Xenoliths collected from the southern part of NGVF originatefrom shallower depth (35-40 km) than those from the central part (40-50 km) [1]. Crystalpreferred orientations (CPO) of the minerals were measured by electron backscatter diffraction(EBSD). Two distinct orientation types based on the distribution and alignment ofcrystallographic axes were recognized, which show some correlation not only with the texturetypes, but also with olivine l-indexes that indicate the strength of the xenolith fabric [2].Samples from the southern part of the NGVF are characterized by lower l-indexes (2.5-3.6) thanthose from the central area (3.5-10.4). In addition, samples with porphyroclastic textures showedtype-A CPO, whereas the others with equigranular textures, exhibited type-D olivine orientation.The different CPO types could be the result of differences in the amount of stress and watercontent of the mantle portion represented by the xenoliths. Based on this assertion, the xenolithsprobably originate from different domains of the lithospheric mantle [1].The seismic properties, i.e. seismic anisotropy and velocities, of these 17 mantle xenoliths werecalculated based on the CPO and volume fractions of olivine, ortho- and clinopyroxene [3]. Itwas found that P wave and fast split shear wave polarization direction is always close to thedensity maximum of the a-axis of olivine. Seismic anisotropy is higher for stronger CPO.Positive, but not linear correlation was observed between the calculated anisotropies and the J-index. Maximum P wave azimuthal anisotropy ranges are 4.5-6.9% and 5.3-11.9%, for thesouthern and the central area, respectively. Maximum S wave polarization anisotropy ranges are2.92-5.31 % and 3.97-7.46% for the southern area and the central area, respectively.The anisotropy that would be measured by SKS, Rayleigh and Love waves for end-memberorientations of the lineation and foliation could be predicted based on the calculated seismicproperties of the xenoliths [4]. The calculated anisotropy is compared to the results of S receiverfunction analysis based on data recorded at 3 nearby permanent seismological stations. The goalof this study is the development of a petrophysical and seismological model for the lithosphericmantle in order to obtain a better interpretation of the measured seismological data, and hencedetermine the current and, if possible, the fossil lithosphere-asthenosphere boundary beneath thestudied area.[lJ Liptai, N. et ai. 2013. (in Hungarian) Bulletin of the Hungarian Geological Society, 143/4, 371-382.[2J Bunge, H. J Texture A nalysis in Materials Sciences. Butterworths, London, 1982, p. 593[3J Mainprice, D. 1990. Compo Geosci. 16,385-393[4J Baptiste, V., Tommasi A. 2014. SE, 5, 45-63.r---------MANAGEMIRSESMEDYNA~C~V,S•• Fth~TNC~TsMAROCREpUBLlQUE FRAN(;AISEAt.UIASSAlll DJ:. FRASCl AU MAROC

Petrophysical and seismological model of the lithospheric mantle beneath the Nógrád-Gömör Volcanic Field (NOrthern Pannonian Basin)

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