Publication Date:
2021-02-10
Description:
Ischia, one active volcano of the Phlegraean
Volcanic District, prone to very high risk, is dominated by
a caldera formed 55 ka BP, followed by resurgence of the
collapsed area. Over the past 3 ka, the activity extruded
evolved potassic magmas; only a few low-energy explosive
events were fed by less evolved magmas. A geochemical
and Sr–Nd–O isotope investigation has been performed on
minerals and glass from products of three of such eruptions, Molara, Vateliero, and Cava Nocelle (\2.6 ka BP).
Data document strong mineralogical, geochemical, and
isotopic heterogeneities likely resulting from mingling/
mixing processes among mafic and felsic magmas that
already fed the Ischia volcanism in the past. Detailed study
on the most mafic magma has permitted to investigate its
origin. The mantle sector below Ischia underwent subduction processes that modified its pristine chemical, isotopic, and redox conditions by addition of B1 % of
sediment fluids/melts. Similar processes occurred from
Southeast to Northwest along the Apennine compressive
margin, with addition of up to 2.5 % of sediment-derived
material. This is shown by volcanics with poorly variable,
typical d18O mantle values, and 87Sr/86Sr progressively
increasing toward typical continental crust values. Multiple
partial melting of this modified mantle generated distinct
primary magmas that occasionally assimilated continental
crust, acquiring more 18O than 87Sr. At Ischia, 7 % of
Hercynian granodiorite assimilation produced isotopically
distinct, K-basaltic to latitic magmas. A SW–NE regional
tectonic structure gave these magmas coming from large
depth the opportunity to mingle/mix with felsic magmas
stagnating in shallower reservoirs, eventually triggering
explosive eruptions.
Description:
Published
Description:
1173 - 1194
Description:
2V. Struttura e sistema di alimentazione dei vulcani
Description:
3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
Description:
4V. Processi pre-eruttivi
Description:
6A. Geochimica per l'ambiente e geologia medica
Description:
JCR Journal
Keywords:
Ischia
;
Mineral chemistry
;
Mingling/mixing
;
Mantle enrichment/
;
crustal contamination
;
Oxidizing fluids
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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