Geochemical and Sr-Nd-Pb isotopic characteristics of Late Cenozoic leucite lamproites from the East European Alpine belt (Macedonia and Yugoslavia) |
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| Authors: | Email author" target="_blank">R?AltherrEmail author H-P?Meyer A?Holl F?Volker C?Alibert M?T?McCulloch V?Majer |
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| Institution: | (1) Mineralogisches Institut, Universität Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany;(2) A. Holl, Willi-Egler-Str. 14, 76189 Karlsruhe, Germany;(3) Institut für Geowissenschaften und Lithosphärenforschung, Universität Giessen, Senckenbergstraße 3, 35390 Giessen, Germany;(4) Centre de Recherches Pétrographiques et Géochimiques, Vandoeuvre-lès-Nancy, France;(5) Research School of Earth Sciences, The Australian National University, 0200 Canberra, Australia;(6) Institute of Mineralogy, Petrology, and Economic Geology, RGN faculty, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia |
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| Abstract: | In the East European Alpine belt, leucite-sanidine-phlogopite-olivine-bearing volcanic rocks of Late Cenozoic age occur at eight localities within the Vardar suture zone and at one locality in the Southern Carpathian fold-and-thrust belt. Most of these volcanics are characterized by high Mg# (66.6–78.6), high abundances of Ni (117–373 ppm) and Cr (144–445 ppm) as well as high primary K2O contents (5.63–7.01 %) and K2O/Na2O values (1.93–4.91). Rocks with more differentiated compositions are rare. A lamproite affinity of these rocks is apparent from their relatively low contents of Al2O3 (9.9–14.3 wt%) and CaO (6.2–8.3 wt%) in combination with high abundances of Rb (85–967 ppm), Ba (1,027–4,189 ppm), Th (18.9–76.5 ppm), Pb (19–54 ppm), Sr (774–1,712 ppm) and F (0.16–0.52 wt%), and the general lack of plagioclase. Although eruption of the magmas took place in post-collisional extensional settings, significant depletions of Nb and Ta relative to Th and La, low TiO2 contents (0.92–2.17 %), low ratios of Rb/Cs, K/Rb and Ce/Pb as well as high ratios of Ba/La and Ba/Th suggest close genetic relationships to subduction zone processes. Whereas Sr and Nd isotope ratios show relatively large variations (87Sr/86Sr = 0.7078–0.7105, 143Nd/144Nd = 0.51242–0.51215), Pb isotope ratios display a very restricted range with 206Pb/204Pb = 18.68–18.88 and variable but generally high  7/4 (11–18) and 8/4 (65–95) values. The observed petrographic, geochemical and isotopic characteristics are best explained by a genetic model involving preferential melting of phlogopite-rich veins in an originally depleted lithospheric mantle source, whereby the metasomatic enrichment of the mantle source is tentatively related to the addition of components from subducted sediments during consumption of Tethyan oceanic lithosphere.Editorial responsibility: J. Hoefs |
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