Klébesz, Rita

Liptai, Nóra

Novák, Attila

Patkó, Levente

Szabó, Csaba

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ACTA UNIVERSITATIS SZEGEDIENSISVolume 9                                                      2015 Published by the Department of Mineralogy, Geochemistry and Petrology, University of SzegedACTA MINERALOGICA-PETROGRAPHICAABSTRACT SERIESACTA MINERALOGICA-PETROGRAPHICAABSTRACT SERIESVOLUME   9   2015HU ISSN 0324-6523HU ISSN 1589-4835th6  Mineral Sciences in the Carpathians ConferenceVeszprém, 16-19 May, 2015ACTAINERALOGCAPETROG  BSTCTES,  21 MI-RAPHICA  ARA SERI9,05ACTA MINERALOGICA-PETROGRAPHICA estabilished in 1923  ABSTRACT SERIES HU ISSN 0324-6523 HU ISSN 1589-4835   Editor-In-Chief Elemér Pál-Molnár University of Szeged, Szeged, Hungary E-mail: palm@geo.u-szeged.hu   Guest Editor Gabriella B. Kiss Eötvös Loránd University, Budapest, Hungary E-mail: gabriella.b.kiss@ttk.elte.hu  Editorial Board Balázs Koroknai  István Főzy Csaba Szabó  István Viczián István Dódony  János Földessy Magdolna Hetényi  Péter Árkai Mihály Pósfai  Péter Sipos Péter Rózsa   Sándor Szakáll Szabolcs Harangi  Tamás Fancsik Tibor Zelenka  Tibor Szederkényi Gábor Papp   Tivadar M. Tóth   Abbreviated title: Acta Mineral. Petrogr. Abstr. Ser., Szeged     Editorial Address H-6701 Szeged, Hungary P.O. Box 651  The Acta Mineralogica-Petrographica Abstract Series is published by the Department of Mineralogy, Geochemistry and Petrology, University of Szeged, Szeged, Hungary  © Department of Mineralogy, Geochemistry and Petrology, University of Szeged   On the cover: The castle of Veszprém (photo by: M. Pósfai) Acta Mineralogica-Petrographica, Abstract Series, 9, 2015 51 Constraints on mantle metasomatism beneath the Nógrád-Gömör volcanic field with combined geochemical and geophysical approaches Patkó, L.1, Klébesz, R.2, Novák, A.2, Liptai, N.1, Szabó, Cs.1 1 Lithosphere Fluid Research Lab, Department of Petrology and Geochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest 1117, Hungary (patkolev@gmail.com) 2MTA Research Centre for Astronomy and Earth Sciences, Geodetic and Geophysical Institute, Csatkai Endre u. 6-8., Sopron 9400, HungaryIn the Carpathian-Pannonian region (CPR) there are five occurrences where Plio-Pleistocene alkali basalts brought upper mantle xenoliths to the surface, providing the opportunity to obtain direct information from greater depths. The northernmost xenolith bearing locality in the CPR is the Nógrád-Gömör Volcanic Field (NGVF) from where new geochemical and geophysical data has been acquired with the aim of proposing a mantle evolution model. After thorough sampling, a xenolith suit was distinguished from the dominant lherzolites, exhibiting anomalous modal composition. These orthopyroxene-poor and clinopyroxene-rich wehrlite xenoliths, which are only present in the central part of NGVF, show particular petrographic features with small (100-200 μm), rounded olivines and vermicular spinel inclusions sitting in irregularly shaped, elongated, relatively large (up to 3 mm) clinopyroxenes. Orthopyroxene remnants can be present in the core of clinopyroxenes, suggesting that clinopyroxene formed at the expense of orthopyroxene.   Besides petrography, major element composition of minerals also reveals differences between lherzolites and wehrlites. Wehrlites shows Fe and Mn enrichment in olivines, Ti, Al and Fe enrichment in clinopyroxenes, and Fe and Ti enrichment in spinels compared to lherzolite xenoliths from the same localities. Trace element geochemistry of clinopyroxenes in wehrlite xenoliths was determined by LA-ICP-MS analyses, and show similar results for each locality: slight enrichment in incompatible elements, including LREE compared to lherzolitic clinopyroxenes. In order to obtain geophysical information of the upper mantle of the NGVF, long period magnetotelluric (MT) measurements were carried out at 14 locations along a ~ 60 km long NNW-SSE profile. As a result, a body with low electric resistivity (high conductivity) was recognized beneath the Moho of the central part of the NGVF. We propose that the wehrlite was formed by interaction of alkali mafic melt with peridotitic wallrock at top of the subcontinental lithospheric mantle beneath the central part of the NGVF. During this event the original lherzolitic upper mantle went through pervasive metasomatism, where orthopyroxene was transformed into clinopyroxene. At 35-50 km depth a low resistivity body was mapped by MT measurements which suggests that the metasomatic agent as small melt pockets connected by glass veinlets might still be present beneath the central part of the NGVF, possibly causing detectable low resistivity.  

Constraints on mantle metasomatism beneath the Nógrád-Gömör Volcanic Field with combined geochemical and geophysical approaches

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