Peralkaline felsic magmatism at the Nemrut volcano,Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV |
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| Authors: | Email author" target="_blank">Ray?MacdonaldEmail author Mari?Sumita Hans-Ulrich?Schmincke Bogus?aw?Bagiński John?C?White S?awomir?S?Ilnicki |
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| Institution: | 1.IGMP Faculty of Geology,University of Warsaw,Warsaw,Poland;2.Environment Centre,Lancaster University,Lancaster,UK;3.Geomar Helmholtz Centre for Ocean Research Kiel,Kiel,Germany;4.Department of Geography and Geology,Eastern Kentucky University,Richmond,USA |
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| Abstract: | Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for ~570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the intermediate-silicic magmas evolved in an upper crustal magma reservoir at temperatures between 1100 and 750 °C, at fO2 close to the FMQ buffer. The silicic magmas either were halogen poor or exsolved a halogen-rich phase prior to or during eruption. An unusual Pb-rich phase, with up to 98.78 wt% PbO, is interpreted as having exsolved from the intermediate-rhyolitic magmas. |
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