Publication Date:
2024-01-30
Description:
This study focus on the Mt Etna December 2018 eruption with the aim of
investigating the geochemical characteristics of the feeding magma. New data
on major and trace element geochemistry of olivine-hosted melt inclusions (MI) in
volcanic products are presented together with the noble gas geochemistry of fluid
inclusions (FI) in olivines. The noble gas geochemistry of fluid inclusions (FIs) in
olivines was also investigated. The major element composition of MIs is variable
from tephrite/trachybasalt to phonotephrite/basaltic trachyandesite, with SiO2 =
45.51–52.72 wt%, MgO = 4.01–6.02 wt%, and CaO/Al2O3 = 0.34–0.72. Trace
element patterns of MIs present a typical enrichment in LILE and LREE,
depletion in HFSE, and relatively fractionated REE patterns: (La/Lu) N=
18.8–41.08, with Eu/Eu* = (0.5–1.8). Positive anomalies in Sr (Sr/Sr* = 0.8–2.3)
and Ba can be ascribed to the assimilation of plagioclase-rich cumulates in the
magmatic reservoir. The variable Ba/La (9.8–15.8), K/Nb (260–1037), Ce/Nb
(1.9–3.4), Rb/La (0.4–1.6), and Ba/Nb (10.8–25.8) ratios reveal mixing between
two types of end-member magmas comparable to those emitted from 1) the
2001 Upper Vents and 2002–03 Northern Fissures (Type-1) and 2) the 2001 Lower
Vents and 2002–03 Southern Fissures (Type-2), respectively. Type-2 represents a
magma that was under the influence of a crustal component, whereas Type-1 is
compatible with a HIMU–MORB-type heterogeneous mantle source. It appears
that the 2018 MIs have captured the two different types of magmas, and the lack of
homogenization may imply a very fast ascent (a few months). Compatible with the
contemporary presence of primordial HIMU–MORB and crust-contaminated
end-members are the data on noble gases from FI that highlighted an 3He/4He
value of 6.5–6.6Ra. The hypothesis of two different types of magmas, identified by
the trace element geochemistry in MIs, is, thus, reinforced by helium isotopic data
on FI of the 2018 eruption together with data from other Etnean eruptions and
allows the inference of a bicomponent magma mixing.
Description:
Published
Description:
1122132
Description:
OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
Description:
JCR Journal
Keywords:
melt inclusions
;
fluid inclusions
;
trace elements
;
noble gases
;
Mt. Etna
;
04.08. Volcanology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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