Metasomatism-induced wehrlite formation in the upper mantle beneath the Nógrád-G?m?r Volcanic Field(Northern Pannonian Basin):Evidence from xenoliths  

作　　者：Levente Patko Nora Liptai Laszlo Elod Aradi Rita Klebesz Eszter Sendula Robert J.Bodnar Istvan Janos Kovacs Karoly Hidas Bernardo Cesare Attila Novak Balazs Trasy Csaba Szabo 

机构地区：[1]Lithosphere Fluid Research Lab,Institute of Geography and Earth Sciences,Eotvos Lor and University,Budapest,Hungary [2]Isotope Climatology and Environmental Research Centre,Institute for Nuclear Research,Hungarian Academy of Sciences,Debrecen,Hungary [3]CCFS-GEMOC,Department of Earth and Planetary Sciences,Macquarie University,Sydney,Australia [4]Geodetic and Geophysical Institute,Research Centre for Astronomy and Earth Sciences,Hungarian Academy of Sciences,Sopron,Hungary [5]Fluids Research Laboratory,Department of Geosciences,Virginia Tech,Blacksburg,VA,United States [6]MTA CSFK Lendület Pannon LitH2Oscope Research Group,Geodetic and Geophysical Institute,Research Centre for Astronomy and Earth Sciences,Hungarian Academy of Sciences,Sopron,Hungary [7]Instituto Andaluz de Ciencias de La Tierra,CSIC&UGR,Armilla,Granada,Spain [8]Department of Geosciences,University of Padua,Padua,Italy [9]Department of Geology,Eotvos Lorand University,Budapest,Hungary

出　　处：《Geoscience Frontiers》2020年第3期943-964,共22页地学前缘（英文版）

基　　金：This research was financially facilitated by Orlando Vaselli;supported by the Bolyai Postdoctoral Fellowship Program,a Marie Curie International Reintegration Grant(Grant No.NAMS-230937);a postdoctoral grant(Grant No.PD101683)of the Hungarian Scientific Research Found(OTKA)to I.J.K.;as well as a grant of the Hungarian Scientific Research Found(Grant No.78425)to Cs.;supported by a grant from the U.S.National Science Foundation(EAR1624589)to R.J.;supported by the GINOP-2.3.2-152016-00009 research program。

摘　　要：Clinopyroxene-enriched upper mantle xenoliths classified as wehrlites are common(~20% of all xenoliths) in the central part of the Nograd-G(o| ")m(o|")r Volcanic Field(NGVF),situated in the northern margin of the Pannonian Basin in northern Hungary and southern Slovakia.In this study,we thoroughly investigated 12 wehrlite xenoliths,two from each wehrlite-bearing occurrence,to determine the conditions of their formation.Specific textural features,including clinopyroxene-rich patches in an olivine-rich lithology,orthopyroxene remnants in the cores of newlyformed clinopyroxenes and vermicular spinel forms all suggest that wehrlites were formed as a result of intensive interaction between a metasomatic agent and the peridotite wall rock.Based on the major and trace element geochemistry of the rock-forming minerals,significant enrichment in basaltic(Fe,Mn,Ti) and high field strength elements(Nb,Ta,Hf,Zr) was observed,compared to compositions of common lherzolite xenoliths.The presence of orthopyroxene remnants and geochemical trends in rock-forming minerals suggest that the metasomatic process ceased before complete wehrlitization was achieved.The composition of the metasomatic agent is interpreted to be a mafic silicate melt,which was further confirmed by numerical modelling of trace elements using the plate model.The model results also show that the melt/rock ratio played a key role in the degree of petrographic and geochemical transformation.The lack of equilibrium and the conclusions drawn by using variable lherzolitic precursors in the model both suggest that wehrlitization was the last event that occurred shortly before xenolith entrainment in the host mafic melt.We suggest that the wehrlitization and the Plio-Pleistocene basaltic volcanism are related to the same magmatic event.

关 键 词：WEHRLITE XENOLITHS Upper mantle METASOMATISM MAFIC silicate melt Trace element modelling 

分 类 号：P581[天文地球—岩石学] P59[天文地球—地质学]