Publication Date:
2023-02-01
Description:
Stromboli (Italy) is a basaltic volcano characterized by persistent, mild strombolian activity, occasionally interrupted by lava
effusion and more violent explosive events, named major explosions and paroxysms depending on their intensity and magnitude.
The normal activity is fed by a shallow and degassed highly porphyritic (HP) shoshonitic basalt carrying about 50 vol.%
crystals settled in a shoshonitic glassy matrix (
K2O 〉 3.8 wt.%). The more energetic explosions erupt a deep, volatile-rich,
low-porphyritic (LP) magma with 〈 10 vol.% crystals in a shoshonitic basaltic glassy matrix (
K2O 〈 2.4 wt.%). Products with
intermediate glass composition are also found in the more violent explosive events. In this study, we present a new data set
of major and trace element contents in matrix glasses and minerals performed in products from different types of explosive
activity that occurred at Stromboli between 1998 and 2020. This large data set is used to put constraints on the evolution
and architecture of the intermediate plumbing system, where the transformation from LP to HP occurs. Results indicate that,
compared to paroxysms, the glassy matrices of the LP pumices from major explosions are richer in incompatible trace elements
(and K2O
wt.%) due to 〈 15 wt.% fractionation of clinopyroxene and olivine. This points to a chemical zoning of the
deep reservoir and suggests that major explosions are fed by magmas residing in its upper part. Among the major explosions,
the homogeneous intermediate glasses in the products from the 19 July 2020 event originate from the interplay of mixing
and crystal fractionation processes. The crystallization of euhedral microphenocrysts of An-rich plagioclase suggests that
batches of magma can pond and crystallize for few days (〈 11) at the base of the intermediate zone of the plumbing system,
at pressure coinciding with the entering of plagioclase into the system (〈 100 MPa). As a relevant point for understanding
the pre- and syn-eruptive magma dynamics, data indicate a positive correlation between the magnitude of the explosions
and the depth of the supply magma.
Description:
Published
Description:
96
Description:
3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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