Subduction-related melt refertilisation and alkaline metasomatism in the Eastern Transylvanian Basin lithospheric mantle: Evidence from mineral chemistry and noble gases in fluid inclusions
| Autor: | Ioan Seghedi, Michel Grégoire, Giacomo Ferretti, Andrea Luca Rizzo, Barbara Faccini, Costanza Bonadiman, Theodoros Ntaflos, Massimo Coltorti |
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| Přispěvatelé: | Faccini, B, Rizzo, A, Bonadiman, C, Ntaflos, T, Seghedi, I, Grégoire, M, Ferretti, G, Coltorti, M |
| Rok vydání: | 2020 |
| Předmět: |
010504 meteorology & atmospheric sciences
Mantle wedge Mantle refertilisation Geochemistry engineering.material 010502 geochemistry & geophysics PE10_10 01 natural sciences Post-collisional Mantle (geology) NO Noble gase Geochemistry and Petrology Lithosphere Fluid inclusions Metasomatism Amphibole 0105 earth and related environmental sciences Basalt Olivine Geology Eastern Transylvanian Basin Mantle refertilisation Noble gases Post-collisional Subduction-related metasomatism Noble gases Subduction-related metasomatism Eastern Transylvanian Basin engineering |
| Zdroj: | Lithos. :105516 |
| ISSN: | 0024-4937 |
| DOI: | 10.1016/j.lithos.2020.105516 |
| Popis: | Calc-alkaline and alkaline magmatic activity is generally separated in space and/or in time. The Eastern Transylvanian Basin in Romania is one of the few places where, during Pleistocene, alkaline eruptions occurred contemporaneously with the calc-alkaline activity. Mantle xenoliths entrained in Persani Mts. alkaline volcanic products have been studied in order to investigate the interaction of metasomatic agents of different magmatic affinities with the mantle wedge. Based on mineral major and trace element and noble gases in fluid inclusions, two main events have been recognized. The first was a pervasive, complete re-fertilization of a previously depleted mantle by a calc-alkaline subduction-related melt, causing the formation of very fertile, amphibole-bearing lithotypes. This is shown by the a) increased amounts of modal clinopyroxene up to 21.9 % with Al2O3 contents up to 8.16 wt%, higher than what is expected for clinopyroxene in Primordial Mantle; b) 4He/40Ar* ratios up to 1.2, within the reported range for mantle production; c) 3He/4He in olivine, opx and cpx of 5.8 ± 0.2 Ra, among the most radiogenic values of European mantle, below the typical MORB mantle value (8 ± 1 Ra), reflecting recycling of crustal material in the local lithosphere. The second event is related to later interaction with an alkaline metasomatic agent similar to the host basalts that caused slight LREE enrichment in pyroxenes and disseminated amphiboles and precipitation of vein amphiboles with a composition similar to amphiboles megacrysts also found in the Persani Mts. volcanic deposits. This is highlighted by the 4He/40Ar* and 3He/4He values found in some opx and cpx, up to 2.5 and 6.6 Ra, respectively, more typical of magmatic fluids. |
| Databáze: | OpenAIRE |
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