Formation Conditions of Leucite-Bearing Lavas in the Bolsena Complex (Vulsini, Italy): Research Data on Melt Inclusions in Minerals
Russian Geology and Geophysics © 2019, V.S. Sobolev IGM, Siberian Branch of the RAS Vol. 60, No. 2, pp. 119–132, 2019 DOI:10.15372/RGG2019009 Geologiya i Geofizika Formation Conditions of Leucite-Bearing Lavas in the Bolsena Complex (Vulsini, Italy): Research Data on Melt Inclusions in Minerals A.T. Isakovaa,, L.I. Paninaa, F. Stoppab a V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia b Dipartimento di Scienze DiSPUTer, Universita degli Studi G. d’Annunzio, via dei Vestini 30, Chieti Scalo (CH), 66100, Italy Received 29 June 2017; received in revised form 9 November 2017; accepted 15 June 2018 Abstract—A melt inclusion study was carried out in the leucite-bearing tephriphonolite and phonolite lavas of the Bolsena complex in order to obtain direct data on the chemical composition of initial melts, their evolution, and their crystallization temperatures. It has been found that the initial melt for the considered rocks was of tephrite–basanite composition. Its crystallization began with the formation of clinopyroxene phenocrysts at 1205–1100 °C, then leucite and plagioclase crystallization took place at about 1120 °C and 1080–1060 °C, respectively. The initial tephrite–basanite melt was slightly enriched in volatile components (H2O, F, SO3, and Cl). During the crystalliza- tion of clinopyroxene, leucite, and plagioclase, the composition of the initial magma changed toward an increase in the contents of SiO2, Al2O3, and K2O and a decrease in the contents of FeO, MgO, and CaO, i.e., evolved toward phonolite. A similar evolution trend is typical of alkaline basic systems.
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