Magma chamber of the Campi Flegrei supervolcano at the time of eruption of the Campanian Ignimbrite

Abstract

A supereruption that occurred in the Campi Flegrei area, Italy, ca. 39 ka had regionaland global-scale environmental impacts and deposited the Campanian Ignimbrite (CI). We attempt to shed light on critical aspects of the eruption (depth of magma chamber, intensive pre-eruptive magma conditions) and the large-volume magma plumbing system on the basis of information derived from analyzing melt inclusion (MI) data. To achieve these aims, we provide new measurements of homogenization temperatures and values of dissolved H 2 O within phenocryst-hosted MIs from pumices erupted during different phases of the CI eruption. The MI data indicate that a relatively homogeneous overheated trachytic magma resided within a relatively deep magma chamber. Dissolved water contents in MIs indicate that prior to the eruption the magma chamber underwent radical changes related to differential upward movement of magma. Decompression of the rising trachytic magma caused a decrease in water solubility and crystallization, and trachytic bodies were emplaced at very shallow depths. The proposed eruptive model links portions of the main magma chamber and apophyses with specific eruptive units.

Crystal fractionation, magma step ascent, and syn-eruptive mingling: the Averno 2 eruption (Phlegraean Fields, Italy)

“…More recently, seismic discontinuities detected at depths of 2.7 and 7.5 km were ascribed to the presence of a gas-bearing fractured rock layer overlying a low velocity zone with ponded partial melts (Zollo et al 2008). The development of a mid-crustal sill-like magma reservoir, as hypothesized from seismic reflection profiles, is consistent with the magma crystallization pressure (*200 MPa) derived from petrological data on the Minopoli 2 eruption (10.2 ka; Mangiacapra et al 2008) and the 39 ka year-old CI trachytic magma (Marianelli et al 2006). It has been suggested ) that smaller, possibly shallower magma pockets fed the eruptions that took place in the PFc system over the past 12 ka.…”

Magma chamber evolution prior to the Campanian Ignimbrite and Neapolitan Yellow Tuff eruptions (Campi Flegrei, Italy)

“…Melt inclusion data of minerals in rocks younger than 39 ka indicate levels of crystallization at different depth: at about 10 and between 8 and 3 km, suggesting the occurrence of both deep and shallow magma reservoirs in the past (Cecchetti et al 2001;Marianelli et al 2006;Civetta and Rutherford, unpublished data).…”

The Vesuvius and the other volcanoes of Central Italy

“…In terms of major element compositions, the difference among these groups is mainly in their K 2 O/Na 2 O ratio and the relative abundance of CaO, Fe 2 O 3 , MgO and Cl. The study of the interstitial glasses and melt inclusions of the Campanian ignimbrite fallout and breccia deposits (Signorelli et al, 1999;Marianelli et al, 2006) indicates a similar compositional variability. Analyses of the breccia museum unit, outcropping in the western sector of the Campi Flegrei, revealed a stratigraphic arrangement of this compositional variability parallel to an upward increase of the less evolved products (Melluso et al, 1995), a connection that was later recognised by Pappalardo et al (2002) in another proximal sequence of the Campanian ignimbrite at Ponti Rossi, East of the Campi Flegrei.…”

“…The magma chamber that fed the Campanian ignimbrite eruption was located between 6 and 8 km depth (Marianelli et al, 2006), and its partial depletion led to the formation of the Campi Flegrei caldera (Fig. 38).…”