Publication Date:
2017-04-04
Description:
Magmatic processes triggering eruptions at Campi Flegrei caldera (southern Italy) and their relationships
with the widespread emissions of fluids and caldera unrest episodes, are poorly constrained. The 4.1 ka B.P.
Agnano–Monte Spina eruption, the reference event for a future large-size explosive eruption at Campi
Flegrei, was investigated to shed light, through melt inclusion and isotope analyses, on the geochemical
processes operating in the plumbing system. Chemical and isotopic data on whole rocks and glasses suggest
that at least two magma batches mixed during the course of the eruption. Melt inclusion data highlight the
pre-eruption storage conditions of two magmatic end-members. One end-member is like the less
differentiated (shoshonitic) Campi Flegrei erupted magma, while the other could be a residual of the
Neapolitan Yellow Tuff magma. Mixing between these two components was driven by a large gas phase
which sustained the ascent of magmas of deep provenance. The H2O and CO2 contents in pyroxene-hosted
melt inclusions yield entrapment pressures between 107 and 211 MPa, corresponding to depths between 4
and 8 km. The degassing trends reveal two extreme patterns. One pattern, already documented in the
literature, is the volatile signature of poorly differentiated magmas ascending from more than 8 km depth,
while the other is related to a gas-dominated magma, flushed by a CO2-rich gas phase partly released from
the deep reservoir. This study provides a conceptual frame for unrest phases at Campi Flegrei, such as the
1982–84 event. Uplift phases can be related to closed-system ascent of magmas and fluids from more than
8 km depth, and their emplacement at shallow levels. This leads the shallow system to store, and then
progressively release, the accumulated gas. In this view, both unrest episodes and eruptions could be
strongly influenced by both the achievement of a critical upper limit of gas storage in the shallow magmatic
reservoir and the stress and fracturing state of the roof rocks. The present results help to constrain the preeruptive
conditions expected at Campi Flegrei caldera in case of a future large-size eruptive event.
Description:
Published
Description:
135–147
Description:
2.3. TTC - Laboratori di chimica e fisica delle rocce
Description:
3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
Description:
JCR Journal
Description:
reserved
Keywords:
Sr and Nd isotopes
;
Melt inclusions
;
Gas flushing
;
Magma mixing
;
04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
;
04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
;
04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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