Publication Date:
2017-04-04
Description:
New major and trace element analyses and Sr-isotope determinations of rocks from Mt. Somma–Vesuvius volcano
produced from 25 ky BP to 1944 AD are part of an extensive database documenting the geochemical evolution of this
classic region. Volcanic rocks include silica undersaturated, potassic and ultrapotassic lavas and tephras characterized by
variable mineralogy and different crystal abundance, as well as by wide ranges of trace element contents and a wide span of
initial Sr-isotopic compositions. Both the degree of undersaturation in silica and the crystal content increase through time,
being higher in rocks produced after the eruption at 472 AD (Pollena eruption). Compositional variations have been
generally thought to reflect contributions from diverse types of mantle and crust. Magma mixing is commonly invoked as a
fundamental process affecting the magmas, in addition to crystal fractionation. Our assessment of geochemical and Srisotopic
data indicates that compositional variability also reflects the influence of crustal contamination during magma
evolution during upward migration to shallow crustal levels and/or by entrapment of crystal mush generated during previous
magma storage in the crust. Using a variant of the assimilation fractional crystallization model (Energy Conservation–
Assimilation Fractional Crystallization; [Spera and Bohrson, 2001. Energy-constrained open-system magmatic processes I:
General model and energy-constrained assimilation and fractional crystallization (EC–AFC) formulation. J. Petrol. 999–
1018]; [Bohrson, W.A. and Spera, F.J., 2001. Energy-constrained open-system magmatic process II: application of energyconstrained
assimilation–fractional crystallization (EC–AFC) model to magmatic systems. J. Petrol. 1019–1041]) we
estimated the contributions from the crust and suggest that contamination by carbonate rocks that underlie the volcano (2
km down to 9–10 km) is a fundamental process controlling magma compositions at Mt. Somma–Vesuvius in the last 8 ky
BP. Contamination in the mid- to upper crust occurred repeatedly, after the magma chamber waxed with influx of new mantle- and crustal-derived magmas and fluids, and waned as a result of magma withdrawal and production of large and
energetic plinian and subplinian eruptions.
Description:
Published
Description:
303– 329
Description:
reserved
Keywords:
Mt. Somma–Vesuvius volcano
;
Sr isotopes
;
Geochemistry
;
Crustal contamination
;
Mantle source
;
Phenocryst entrapment
;
04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
;
04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
;
05. General::05.02. Data dissemination::05.02.01. Geochemical data
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
879803 bytes
Format:
application/pdf
