Title: Petrogenesis of Vesuvius historical lavas constrained by Pearce element ratios analysis and experimental phase equilibria
Abstract: Petrogenesis of Vesuvius historical lavas erupted in the interval 1631–1944 was investigated by petrological methods and experimental phase equilibria. Lavas are strongly porphyritic with principal phenocrysts of clinopyroxene, leucite and calcic plagioclase. Olivine, biotite, FeTi oxides and apatite are present occasionally. Their bulk composition defines a chemical group spanning the leucite-tephrite and phonolite-tephrite regions of the TAS (total alkalies vs. silica) diagram. Through PERs (Pearce element ratios) analysis it has been possible to determine the lava differentiation relationships (controlled by cpx joined by minor lc, plag and Ti-mt) and to estimate the extent of differentiation processes (about 25% of initial mass). Chemistry of cpx indicates a multistage crystallization process in the upper crust. The crystallization environmental parameters deduced from the experimental cpx and liquids are consistent with the existence of a shallow magma chamber within the carbonate rocks of the Triassic basement where the nearly dry Vesuvius magma becomes CO2 saturated. The generally small volume of the products from single eruptions, and Vesuvius lavas geochemical and petrographic features suggest magma reservoir is zoned with respect to temperature and phenocrysts abundance. The dynamics of magma withdrawal controls mixing of the melt fractions proceeding from different areas of the magma chamber and, therefore, it produces the within-flow chemical differences. Chemical variations among the lavas of different eruptive cycles are instead believed to be controlled essentially by the speed of magma ascent through the upper crust allowing differential removals of cpx phenocrysts crystallized from the magma on its way to the surface.
Publication Year: 1993
Publication Date: 1993-11-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 41
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