ArticlePDF Available

Compositional variations of magmas in the Aeolian arc: implications for petrogenesis and geodynamics

  • INGV Istituto Nazionale di Geofisica e Vulcanologia

Abstract and Figures

The volcanic rocks of the Aeolian arc exhibit important within-island and along-arc compositional variations that testify to both geochemical heterogeneous mantle sources and different roles and intensities of shallow-level magmatic evolution processes. Calcalkaline magmas are present on all islands, but dominate in the western arc and at Lipari and Panarea. Shoshonitic rocks are present on the central-eastern islands and are particularly abundant at Vulcano and Stromboli. Mafic and intermediate rocks comprise the bulk of older volcanic sequences for most islands. Rhyolites are restricted to younger activity of the central arc, and become particularly abundant at Lipari and Vulcano. Regional variations of incompatible trace element ratios and Sr-, Nd-, and Pb-isotope signatures in mafic-intermediate rocks document the variable composition of mantle sources, which were contaminated by different types of metasomatic fluids released from an oceanic slab in the western-central sectors and from oceanic slab plus sediments in the east. This metasomatism was superimposed over a heterogeneous mantle wedge, which had a mid-ocean-ridge basalt (MORB-) to ocean-island basalt (OIB)-type character passing from the centre to the margins of the arc. The OIB-type component in the external arc is attributed to asthenospheric mantle inflow from the Africa foreland, around the borders of a narrow slab during rollback.
Content may be subject to copyright.
Geological Society, London, Memoirs
doi: 10.1144/M37.15 2013, v.37; p491-510.Geological Society, London, Memoirs
A. Peccerillo, G. De Astis, D. Faraone, F. Forni and M. L. Frezzotti
petrogenesis and geodynamics
Chapter 15 Compositional variations of magmas in the Aeolian arc: implications for
Email alerting to receive free e-mail alerts when new articles cite this article hereclick
Permission to seek permission to re-use all or part of this article hereclick
Subscribe Collection
to subscribe to Geological Society, London, Memoirs or the Lyellhereclick
© The Geological Society of London 2013
at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from at Instituto Nazionale Di Geofisica e Vulcanologia on October 28, 2013 from
Chapter 15
Compositional variations of magmas in the Aeolian arc: implications for
petrogenesis and geodynamics
Dipartimento di Scienze della Terra, Universita
`di Perugia, Piazza Universita
`1, 06100 Perugia, Italy
INGV (Istituto Nazionale di Geofisica e Vulcanologia), Sezione di Sismologia e Tettonofisica,
Via di Vigna Murata 605, 00143 Roma, Italy
Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum,
`di Bologna, Piazza Porta S.Donato 1, 40126 Bologna, Italy
Dipartimento di Scienze dell’Ambiente e del Territorio e di Scienze della Terra,
`di Milano Bicocca, Piazza Della Scienza 4, 20126 Milano, Italy
*Corresponding author (e-mail:
Abstract: The volcanic rocks of the Aeolian arc exhibit important within-island and along-arc compositional variations that testify to
both geochemical heterogeneous mantle sources and different roles and intensities of shallow-level magmatic evolution processes. Calc-
alkaline magmas are present on all islands, but dominate in the western arc and at Lipari and Panarea. Shoshonitic rocks are present on the
central-eastern islands and are particularly abundant at Vulcano and Stromboli. Mafic and intermediate rocks comprise the bulk of older
volcanic sequences for most islands. Rhyolites are restricted to younger activity of the central arc, and become particularly abundant at
Lipari and Vulcano. Regional variations of incompatible trace element ratios and Sr-, Nd-, and Pb-isotope signatures in mafic-intermedi-
ate rocks document the variable composition of mantle sources, which were contaminated by different types of metasomatic fluids
released from an oceanic slab in the western-central sectors and from oceanic slab plus sediments in the east. This metasomatism
was superimposed over a heterogeneous mantle wedge, which had a mid-ocean-ridge basalt (MORB-) to ocean-island basalt (OIB)-
type character passing from the centre to the margins of the arc. The OIB-type component in the external arc is attributed to astheno-
spheric mantle inflow from the Africa foreland, around the borders of a narrow slab during rollback.
Aeolian arc magmatism (Fig. 15.1) exhibits strong within-island
and regional variations in elemental and isotopic compositions.
These are the integrated effects of a variety of different processes
that include heterogeneity of the mantle sources, variable physico-
chemical conditions during magma formation and complex geo-
chemical evolution during magma ascent to the surface (e.g.
Keller 1982; Francalanci et al. 1989, 2004, 2007; Peccerillo 2005).
Intra-crustal magma compositional evolution was the latest
process to occur and therefore left the best evidence in the petrolo-
gical and geochemical signatures of subaerial volcanic rocks. Much
more difficult to understand are the compositional characteristics
and conditions of melting within mantle wedge. This is generally
accomplished by studying the compositions of mafic magmas
erupted along the arc, based on the assumption that these are
reliable proxies of their mantle sources. However, it has been
demonstrated that complex evolution processes in the Aeolian arc
also affected mafic magmas which, in some cases, are more
heavily contaminated by wall rocks than the coexisting intermedi-
ate magmas (see Peccerillo & Wu 1992; Peccerillo et al. 1993,
2004; Santo et al. 2004; Lucchi et al. 2013a). This makes the under-
standing of source composition and evolution processes a parti-
cularly challenging problem, which is still a subject of debate.
This paper is a critical review of the petrology and geochemistry
of the Aeolian arc magmatism and of current ideas regarding the
origin and evolution of magmas, mantle source compositions
and their geodynamic significance. The paper consists of two
parts. The first part is based on literature data and summarizes
the volcanological and structural setting of the arc, describes the
first-order compositional variation of rocks in the single islands
and at the regional scale and discusses the nature and effects of
magma evolution processes. The second part deals with regional
variations of trace elements and radiogenic isotope compositions
of magmas and their mantle sources and discusses the most
popular hypotheses regarding mechanisms and effects of mantle
metasomatism, conditions of formation of shoshonitic and
calc-alkaline magmas and the geodynamic setting of the Aeolian
arc. Along-arc geochemical variations are examined based upon
new LAICPMS (Laser Ablation Inductively Coupled Plasma
Mass Spectrometry) trace element analyses for a large number of
representative samples from across the Aeolian arc. Intermediate
rocks are considered along with mafic rocks, since andesites
from some islands show the most primitive isotopic compositions
across the arc and therefore represent more reliable proxies of
mantle sources than mafic rocks. The new analyses provide an
internally consistent set of data that overcomes the problems of
inter-laboratory analytical bias, a main limitation of data in the lit-
erature. These data offer a better insight into fine-scale regional
geochemical zoning, thus providing a foundation for development
of a comprehensive model of the mantle source composition and
its geodynamic significance.
Structural, volcanological and petrological outlines
The Aeolian volcanism consists of seven main islands (Alicudi,
Filicudi, Salina, Lipari, Vulcano, Panarea and Stromboli) making
up a volcanic arc and several seamounts (Marsili, Eolo, Enarete,
Sisifo, Lametini, Alcione, and Palinuro). These have formed
around and inside the Masili basin (Fig. 15.1), a rapidly expand-
ing back-arc basin (Nicolosi et al. 2006) floored by basaltic
rocks and characterized by thin lithosphere and crust (Trua et al.
2004). The arc exhibits strong lateral variation of structural,
volcanological and petrological characteristics, which make the
Aeolian volcanoes an important case study for subduction-
related volcanism.
From:Lucchi, F., Peccerillo, A., Keller, J., Tranne,C.A.&Rossi, P. L. (eds) 2013. The Aeolian Islands Volcanoes. Geological Society, London, Memoirs, 37,
491510. #The Geological Society of London 2013. Publishing disclaimer:
Stuctural and volcanological setting
The Aeolian volcanoes are composite structures formed by the
superposition of multiple centres and recurrent volcanic and tec-
tonic events, with many sector and central collapses. Rocks
exposed above the sea level are younger than c. 270 ka (Gillot
1987; Leocat 2011). Vulcano and Stromboli are presently active,
but Lipari and Panarea have also erupted or demonstrated
intense submarine degassing during historical time. Of the sea-
mounts, Marsili and Palinuro are considered active. Marsili rises
for more than 3000 m over the sea floor of the Marsili basin, and
is the best studied among Aeolian seamounts (Trua et al. 2011).
The Aeolian islands are constructed upon the Calabro Pelori-
tano basement, a block of the European continent which detached
from Sardinia Corsica and migrated south-westwards during the
Miocene Quaternary opening of the Tyrrhenian Sea. Crustal
thickness beneath the Aeolian arc is c. 15 25 km, and increases
westwards. The Aeolian arc is cut by a complex pattern of fault
systems (Ventura 2013). The NW SE-trending Tindari Leto-
janni Fault (TLF) is the most important tectonic lineament in the
area, running from the Salina Lipari Vulcano alignment to the
Malta escarpment (Fig. 15.1). In mainland Sicily, the TLF cuts
the Calabro Peloritano basement near the boundary with the post-
Miocene accretionary prism and the Iblei continental block to the
west (Grasso 2001). It is likely that these geometric relationships
continue in the Aeolian arc. This implies that distinct types of base-
ment rocks are present across the Aeolian archipelago, that is, the
Calabro Peloritano basement in the central-eastern sectors and
the accretionary prism rocks under the western islands. Such a
hypothesis is supported by the increase in crustal thickness west
of the Tindari Letojanni Fault (Ventura 2013).
Traditionally, the Aeolian arc has been divided into three main
sectors the western, the central and the eastern arcs which are
characterized by first-order volcanological, magmatic and struc-
tural differences (Peccerillo 2005; Ventura 2013). The western
arc is formed by Alicudi and Filicudi, which are situated along
east west- to WNW ESE-striking fault systems. A NNW SSE
compressive strain field due to the Africa Eurasia convergence
is active in this sector (Ventura 2013). The central islands of
Vulcano and Lipari are located along the TLF, where a strike-slip
strain regime is active. Salina is sited at the intersection between
the east west-trending structures of the western arc and the
Tindari Letojanni Fault. Panarea and Stromboli are situated
along SW NE-trending faults. An extensional tectonic regime
affects this sector of the arc.
Active volcanism occurs along the Tindari – Letojanni Fault and
east of this tectonic line. The compressive tectonic regime in the
western sector inhibits upraise and eruption of magmas, whereas
extensional and strike-slip strain regimes in the central-eastern
arc generate vertical faults that are pathways along which
magmas ascend and erupt at the surface (Ventura 2013).
Geophysical studies (e.g. Panza et al. 2003) indicate that deep
seismicity (up to 550 km) only occurs east of the Tindari Leto-
janni Fault. This is a consequence of the Ionian slab subduction
beneath the Calabro Peloritano basement and the southern Tyr-
rhenian Sea. Active Aeolian volcanism is therefore located
above or at the margin of the deep seismicity zone.
Magma compositions
Key geochemical data from the literature are shown in Figures
15.2– 15.6. The important information contained in these diagrams
can be summarized as follows.
(1) Calc-alkaline (CA) and high-K calc-alkaline (HKCA) rocks
occur throughout the arc but dominate at Alicudi, Filicudi,
Salina, Lipari and Panarea (Fig. 15.2). In contrast, shosho-
nites (SHO) are spatially restricted to the central-eastern
islands, where they generally appear during the mature to
late stage of volcanic activity. The Marsili seamount has a
CA basalt to basaltic andesite composition, with a few ande-
sites (Trua et al. 2011). A single sample has ocean-island
basalt (OIB)-type affinity and is not plotted in the diagrams.
The small number of analyses available for the other Aeo-
lian seamounts (not shown) indicates that rocks are predomi-
nantly of calc-alkaline mafic to intermediate composition,
with a few shoshonites (Eolo, Enarete) and arc tholeiites
(Marsili basin margin; Trua et al. 2004; Peccerillo 2005).
(2) The degree of magma evolution increases from the external
to the central islands; rhyolitic volcanism (SiO
.70%) is
present at Panarea and Salina, and becomes abundant at
Lipari and Vulcano (Fig. 15.2). Rhyolites characterize the
younger stages of activity for all these volcanoes.
(3) Abundances of elements that are incompatible with main
magmatic minerals (e.g. Th, U, Nb, Ta and Light Rare
Earth Elements - LREE) increase with silica for all the islands
and seamounts (Fig. 15.3). The exception observed is for
Ba, which decreases in the rhyolites of Vulcano and Lipari,
but not in the rhyolites of Salina and Panarea (Fig. 15.3d).
(4) Incompatible trace element (ITE) abundances increase from
CA to SHO volcanics for the mafic-intermediate compo-
sitions (Fig. 15.4). This is observed for both the large-ion
lithophile elements (LILE: Rb, Ba, La, Th, etc.) and for the
high-field-strength elements (HFSE: Nb, Ta, Hf, Zr).
However, there are several differences between islands.
These have important petrogenetic implications, and will
be discussed later (see “Isotope and trace element compo-
sition of mantle sources”).
(5) Incompatible element patterns normalized to primordial
mantle for basalts and basaltic andesites from the Aeolian
islands and Marsili seamount display the typical features of
arc volcanics worldwide, with enrichments in LILE and rela-
tive depletion in HFSE (Fig. 15.5). Most of these features are
also shown by the Calabro Peloritano basement and the
Ionian Sea sediments (Fig. 15.5d). The Aeolian seamounts
(not shown) show similar patterns as the other Aeolian
rocks, with fractionation and abundances of ITE increasing
from CA to SHO rocks.
(6) Sr-isotope ratios of mafic intermediate rocks increase from
the western island of Alicudi to the central and eastern
islands, reaching maximum values at Stromboli (Fig.
15.6a). Sr Nd isotopic ratios display the well-known
Palinuro Smt.
Glauco Smt.
Eolo Smt.
Sisifo Smt.
Lametini Smt.
Alicudi Filicudi
Alcione Smt.
Enarete Smt.
Fig. 15.1. Location map of Aeolian islands and seamounts. TLF is the Tindari –
Letojanni Fault system.
negative correlation. However, a slightly steeper slope
characterizes the western-central islands. Marsili shows a
large Sr Nd isotope variation that overlaps the western-
central arc domain. Panarea has a variable Sr-Nd isotopic
composition, with CA rocks falling within the field of
western islands and SHO rocks plotting with Stromboli.
At Stromboli there is a considerable increase of Sr- and a
concomitant decrease of Nd-isotopic ratios from calc-alka-
line to shoshonitic rocks (Francalanci et al. 1988, 1989,
2013), which is not observed at Vulcano (De Astis et al. 2000).
He (R/R
) ratios (not shown) range from
7.07 (Alicudi) to 2.51 (Stromboli) (Martelli et al. 2008).
(7) Pb-isotope ratios have variable and overlapping values for
most islands except for Stromboli, which has a distinctively
less radiogenic Pb-isotope composition. Overall, Pb-isotope
ratios fall between the highly radiogenic Etna OIB-type
basalts and the continental crust of the Calabro Peloritano
basement (Fig. 15.6b). Etna is close to the so-called FOZO
(¼FOcus ZOne; Hart et al. 1992) mantle composition,
which is extremely common in anorogenic settings of
Europe and has been termed the European Asthenospheric
Reservoir (EAR) by Wilson & Downes (1991). The
Pb-isotope composition of Marsili overlaps Stromboli and
some of the western-central islands.
(8) Stromboli shows similar radiogenic isotope signatures as
Vesuvio (De Astis et al. 2000, 2013; Peccerillo 2001) and
other volcanoes from Campania. Such a similarity is also
observed for several incompatible trace element ratios, and
led Peccerillo (2001) to conclude that Vesuvio and other
Campania volcanoes represent the northern end of the
Aeolian arc rather than the southern sector of the Roman
Magmatic Province, as generally acknowledged.
Shallow-level magma evolution
Fractional crystallization, crustal assimilation, magma mixing or
some combination of these processes has been documented for
the Aeolian volcanoes. These have been extensively discussed
within individual chapters of this volume, so are only summarized
briefly here.
Fractional crystallization
Fractional crystallization was the predominant process of magma
evolution at several centres. This process was much more
intense for the volcanoes of the central islands, where rhyolitic
compositions were reached. This outcome is likely related to
local tectonics associated with the Tindari Letojanni transcurrent
fault, where the development of pull-apart basins favoured the for-
mation of large reservoirs (Barberi et al. 1994) in which magmas
ponded and fractionated. Mafic minerals plus plagioclase were
main fractionating phases, as demonstrated by curvilinear trends
for many major and trace elements, especially MgO, Ni, Cr but
also Al
and Sr, against SiO
(Fig. 15.3). A decrease of Ba in
the rhyolites of Vulcano and Lipari, but not at Panarea and
Salina, indicates significant separation of alkali-feldspar late in
the evolution stages of the two former islands. Alkali-feldspar
crystallization is related to the HKCA to SHO affinity of late
erupted magmas at Lipari and Vulcano. Fractional crystallization
modifies major and trace element abundances of magmas, slightly
modifies d
O‰, but leaves radiogenic isotope compositions and
incompatible trace element ratios unaffected. The values of these
parameters measured in evolved rocks can therefore be used to
infer compositions of primary melts and their mantle sources.
However, the main problem is that magma evolution rarely (if
ever) occurs simply by closed-system fractional crystallization;
wall-rock assimilation and magma mixing usually accompany
fractional crystallization in most cases.
Magma mixing/mingling
Magma mixing/mingling is widespread in the Aeolian volcanoes.
The most striking evidence of this process is seen in the occurrence
of abundant mafic enclaves in many intermediate and silicic lavas.
These enclaves are blobs of mafic magmas that were present within
the volcanic system and were intermingled with the silicic melts
during eruption. The best examples are observed for some Lipari
and Vulcano rhyolites (e.g. De Rosa & Sheridan 1983; Gioncada
et al. 2005; Perugini et al. 2007; De Astis et al. 2013; Forni
et al. 2013), for Panarea dacites and rhyolites (Calanchi et al.
K2O %
50 55 60 65 70 75 80
K2O %
SiO2 %
K2O %
Eastern arc
Western arc
Central arc
Fig. 15.2. K
O v. SiO
classification diagrams for the Aeolian arc volcanics.
Lines dividing arc tholeiitic (TH), calc-alkaline (CA), high-K calc-alkaline
(HKCA) and shoshonitic (SHO) series are from Peccerillo & Taylor (1976).
Data on Marsili are from Trua et al. (2011). For source of other data see
Peccerillo (2005).
2002; Lucchi et al. 2013d) and at Salina (Perugini et al. 2004;
Lucchi et al. 2013c). Mixing processes also affected most (if not
all) of the magmas however, although physical evidence is less
strong either because of the lack of compositional contrast
between end-members or because near-equilibrium conditions
were reached by hybrid magmas.
Mixing is a complex process of major geochemical and volcano-
logical interest. Detailed studies in the Aeolian arc are however
limited (e.g. De Rosa & Sheridan 1983; De Astis et al. 1997; Gion-
cada et al. 2003, 2005; Perugini et al. 2004, 2007; Davı
`et al. 2008;
Piochi et al. 2009), and the effects on magma compositions for
single eruptions, for individual volcanic centres and at the regional
scale, are still basically unexplored.
Magma contamination
Magma contamination by crustal wall-rocks in the Aeolian volca-
noes took place as a consequence of several different processes.
Assimilation plus fractional crystallization (AFC) is the most
common case, and has been recognized at several islands (e.g.
Salina, Vulcano and Lipari; Crisci et al. 1991; Esperanc¸a et al.
1992; De Astis et al. 2013; Forni et al. 2013; Lucchi et al.
2013c). This is clearly demonstrated by the positive correlations
Sr and d
O‰ with silica observed for many Aeolian
islands by Ellam & Harmon (1990). More complex processes of
combined fractional crystallization, assimilation, refilling of
magma chambers, mixing and frequent tapping by eruptions
(RFTA: refilling, fractionation, tapping, assimilation) have been
recognized for the lowest exposed volcanic sequences of many
islands (e.g. De Astis et al. 1997; Di Martino et al. 2011; Lucchi
et al. 2013a,b, c). These rocks are generally mafic in composition
and display rather variable trace element and isotopic signatures,
which is typical of RFTA processes (O’Hara 1977). Finally, a par-
ticular type of assimilation is represented by incorporation of
different amounts of crustal rocks by basaltic and andesitic
magmas, with the former being able to assimilate greater
amounts of crustal rocks than andesites. Such a process has been
l2O3 %
45 50 55 60 65 70 75 80
SiO2 %
Rb ppm
Ba ppm
Ta ppm
45 50 55 60 65 70 75 80
La ppm
Marsili (a)(b)
Ni ppm
SiO2 %
Fig. 15.3. Variation diagrams of some
major and trace elements v. silica. Source of
data and symbols as in Figure 15.2.
Ta p pm
Sr ppm
0 2 4 6
Zr ppm
K2O wt%
0 2 4 6
La ppm
K2O wt%
Rb ppm
Ba ppm
Fig. 15.4. Incompatible trace element
v. K
O diagrams for mafic-intermediate
rocks (SiO
,56 wt%) from the Aeolian arc
and Marsili seamount, showing increase of
element abundances from calc-alkaline to
shoshonitic rocks. Source of data as in
Figure 15.2.
Rock/Primitive Mantle
Rock/Primitive Mantle
Ta K La
Y Yb
Rock/Primitive Mantle
Ta K La
Y Yb
Rock/Primitive Mantle
Calabrian crust
Ionian sediments
Filicudi Lipari
Local MORB
Etna basalt
Fig. 15.5. Incompatible element patterns
normalized to primordial mantle
compositions for representative
mafic-intermediate rocks (SiO
,56 wt%)
from the Aeolian islands and Marsili
seamount (source of data as in Fig. 15.2).
Ionian sediments (average of two samples;
De Astis, unpublished data), averages of the
Calabro– Peloritano basement (Rottura
et al. 1991), Tyrrhenian MORB (Dietrich
et al. 1977) and Etna basalts (Viccaro &
Cristofolini 2008) are also shown.
Normalizing data are from Sun &
McDonough (1989).
well documented at Alicudi, where evolved andesites were less
affected by assimilation and, consequently, exhibit more primitive
isotopic compositions (i.e. lower Sr- and O- and higher Nd Pb
isotope ratios) than associated basalts (Peccerillo & Wu 1992; Pec-
cerillo et al. 1993; Lucchi et al. 2013a). The same process has been
recognized, although less clearly, at Filicudi (Santo & Peccerillo
2008; Lucchi et al. 2013b).
Several studies on Aeolian volcanoes demonstrated that
magma wall-rock interaction produced an increase in both
Sr and d
O‰ (Ellam & Harmon 1990; Peccerillo et al.
2004; Santo & Peccerillo 2008). However, whereas O-isotope
ratios were increased from typical mantle values of d
O‰ c.
þ5.5 to values as high as d
O‰ c. þ8.5, Sr isotope ratios were
less strongly modified. Detailed studies of two contaminated
suites of mafic magmas from Alicudi and Vulcano (Primordial
Vulcano and Piano Caldera) have shown that extensive crustal
assimilation generated an increase in Sr isotope ratios by five to
six digits on the fourth decimal place (De Astis et al. 1997,
2013; Lucchi et al. 2013a). This is one order of magnitude lower
than the variation observed over the Aeolian arc. Some incompa-
tible element ratios, such as Rb/Ba, Rb/Sr and Ba/K, are signifi-
cantly correlated with Sr-isotope variation, suggesting they were
modified by contamination. By contrast, other element ratios
such as Ba/La, Rb/Nb, U/Th, Sr/Nd and Tb/Yb do not show
any correlation with Sr isotope ratios, implying that they were
less affected or unaffected by contamination. Such different be-
haviour is related to the variable compositional contrast between
magma and wall rocks for various elements. This changes from
one volcanic centre to another however, and results found at
Alicudi and Vulcano cannot be considered as valid for the entire
Aeolian arc.
Conditions of magma ponding and ascent
Conditions of magma ponding, crystallization and ascent have
been examined using two different approaches. One is based on
measurements of crystallographic parameters of clinopyroxenes,
especially cell dimensions, under the assumption that these
depend on pressure of crystallization (e.g. Nazzareni et al. 1998,
2001). Other work has focused on fluid inclusions in quartz-rich
xenoliths (Frezzotti et al. 2003, 2004; Zanon et al. 2003; Frezzotti
& Peccerillo 2004; Peccerillo et al. 2006; Di Martino et al. 2010,
Clinopyroxene studies have documented crystallization at
different pressures within the volcanic systems, suggesting the
occurrence of various depths of magma storage and fractionation
at the regional scale. Fluid inclusion studies provided additional
insight into magma evolution, confirming polybaric mineral crys-
tallization and demonstrating that mafic to intermediate magmas
ponded in deep reservoirs sited at depths of 2118 km in the
lower crust at the mantle-crust boundary. Here, magmas were sub-
jected to fractionation and assimilation processes, plus intensive
feeding by mantle-derived mafic melts (RFTA). At Lipari, long-
lived hot mafic magma reservoirs facilitated partial melting of
the lower continental crust, as testified by the eruption of
cordierite-, garnet-, and sillimanite-bearing lavas (Barker 1987;
Di Martino et al. 2011). By contrast, dacitic and rhyolitic
magmas were generated by dominant fractional crystallization of
mafic parental magmas in reservoirs located at depths of 15
12 km. Since felsic magmas are restricted to the younger stages
of activity at many Aeolian volcanoes, an overall upward
migration of the magma chambers with time has been suggested
(Peccerillo et al. 2006). The reasons for such a migration are
still poorly understood. A variation of local tectonic stress may
have allowed formation of mid-crustal reservoirs (Ventura
2013). Another possibility could be that there was a decrease in
the input of mafic magmas into the deep reservoirs during the
mature to latest (and vanishing?) stages of volcanism. This
would have allowed fractional crystallization to become dominant
with respect to input and mixing with fresh mafic magmas, favour-
ing the formation of evolved melts. These were able to rise more
readily than mafic magmas to shallow crustal levels because of
their lower density.
Mantle source composition, magma genesis
and geodynamic setting
Trace element and isotope data are crucial for understanding the
composition and evolution of mantle sources and for exploring
conditions of magma genesis and geodynamic evolution. Many
geochemical studies have therefore been carried out on the
Aeolian volcanoes. Much attention has been focused on mafic
magmas, under the assumption that they represent primary compo-
sitions. However, such a statement has been proven incorrect for
some mafic magma suites such as at Alicudi and Filicudi. The
possible effects of magma contamination have to be considered
before inferring compositions of primary melts and their
mantle sources.
Isotope and trace element composition of mantle sources
Regional variations of radiogenic isotope ratios for mafic rocks in
the Aeolian arc have long been recognized and attributed to
0.703 0.704 0.705 0.706 0.707 0.708
18.00 19.00 20.00
Fig. 15.6. SrNdPb isotopic compositions for mafic-intermediate rocks
,56%) from the Aeolian arc and Marsili seamount. Source of data and
symbols as in Figures 15.2 and 15.4. Alicudi and Filicudi andesites
¼5662%) are also plotted, since these represent the least-contaminated
magmas in the Aeolian arc (see text). Average Etna basalts (Viccaro &
Cristofolini 2008) and compositions fields of Vesuvio (for source of data see
Peccerillo 2005) and CalabroPeloritano basement (Rottura et al., 1991) are
also reported. NHRL (Northern Hemisphere Reference Line) is from Hart
heterogeneities of the mantle wedge (e.g. Ellam et al. 1988; Ellam
& Harmon 1990; Francalanci et al. 1993; De Astis et al. 2000;
Peccerillo et al. 2004). However, the common occurrence of
magma crust interaction raises the problem of how much of this
variation is due to magma contamination and how much to
source heterogeneity.
Combined O- and Sr-isotope studies can help to discriminate
magma contamination from source contamination processes.
Figure 15.7 represents a d
O‰ and
Sr diagram for the
available data on Aeolian rocks and separated phases (Ellam &
Harmon 1990; Peccerillo et al. 2004; Santo & Peccerillo 2008;
De Astis, unpublished data). The solid line describes a model of
bulk mixing between a primordial mantle source and Ionian Sea
sediments. Only a small number of samples from Alicudi and a
few from Filicudi plot on or just above the mantle sediment
mixing line. By contrast, most of the Filicudi samples are shifted
upwards and show high d
O‰, which is typical of contaminated
magmas. Well-defined vertical trends are shown by Salina and
Vulcano samples, whereas Stromboli shows scattering and plots
away from the mantle sediment mixing line.
Although the above model has to be considered as broadly quali-
tative because of the simplistic assumptions of simple bulk mixing
and uniform compositions for end-members, O Sr isotope data
indicate that a few of the Alicudi and Filicudi magmas can be con-
sidered as near-primary in composition. Their different Sr-isotope
signatures at the same d
O‰ value suggest less radiogenic Sr
compositions for Alicudi magmas and their sources. The vertical
data arrays for Vulcano and Salina highlight strong variation of
O with a modest increase of
Sr, typical of magma con-
tamination (Ellam & Harmon 1990). However, if these trends
are extrapolated back to the mantle sediment mixing line,
Sr-isotope ratios similar to those at Filicudi are deduced (i.e.
Sr slightly higher than 0.704). Stromboli does not show
typical magma contamination trends but no samples fall on the
mantle sediment mixing line, suggesting that the Stromboli
magmas are also contaminated but that Sr-isotope compositions
are more variable and radiogenic than at other islands.
To summarize, the O Sr isotope data suggest that there are few
uncontaminated magmas in the Aeolian arc. Magma contami-
nation processes had minor effects on Sr isotope ratios however,
in agreement with studies on Alicudi and Primordial Vulcano
discussed previously (see “Shallow-level magma evolution”).
This leads to the conclusion that first-order Sr-isotope varia-
tion along the Aeolian arc is a direct manifestation of source het-
erogeneity. The same can be demonstrated for other radiogenic
Variations of Sr Pb isotope ratios along the arc are shown in
Figure 15.8, to better highlight regional isotopic zoning. There is
an increase of the
Sr ratio from Alicudi to Filicudi and
the central islands, where the lowest Sr-isotope values are slightly
above 0.704. Another increase in radiogenic Sr is observed at
Stromboli. Nd isotopic compositions exhibit a similar trend,
although anti-corrrelated with Sr-isotope variations. Ranges of
Pb-isotope ratios remain fairly constant across most of the arc,
but become less radiogenic at Stromboli. The back-arc Marsili sea-
mount has a rather wide range of Sr Nd isotope compositions,
comparable to those observed over the entire western arc. A very
Pb is observed for one sample from Lipari (Esper-
anc¸a et al. 1992).
Trace element abundances and ratios provide additional infor-
mation on mantle composition. Here, this issue is examined by
using a new set of trace element data (Table 15.1) for more than
90 mafic intermediate rocks from different stratigraphic levels
on various islands. The new data have the advantage of minimizing
the inter-laboratory analytical bias that characterizes the data in the
literature, thus providing a confident picture of geochemical
zoning along the arc. Inferences on source composition are
based on trace element contents of both mafic and intermediate
rocks, since andesitic rocks at Alicudi have been shown to rep-
resent the least contaminated magmas across the entire arc (Pec-
cerillo et al. 1993; Lucchi et al. 2013a). Moreover, only trace
element ratios that have not shown systematic variation with
Sr-isotope ratios in the contaminated mafic rocks of Vulcano and
Alicudi are considered, under the assumption that they may
provide reliable information on mantle compositions. The
0.702 0.704 0.706 0.708
2 4
Mantle contamination trend
Fig. 15.7. d
Sr for Aeolian magmas. The solid line represents the
mixing trend between primordial mantle and Ionian sediments (mantle
contamination). Numbers along the line are the amounts of sediments involved
in the mixing. Arrows mimic effects of magma contamination by crustal wall
rocks: note strong oxygen isotope variation and modest increase of Sr isotope
ratios. Data for Filicudi, Alicudi and Vulcano have been determined on
separated clinopyroxene phenocrysts (Peccerillo et al. 2004; Santo & Peccerillo
2008; De Astis, unpublished data) and melt compositions have been calculated
considering high-temperature isotope fractionations. Data on the other islands
are bulk rock determinations (Ellam & Harmon 1990; Gertisser & Keller 2000).
Symbols as in Figure 15.4.
West East
West East
Salina Lipari
Fig. 15.8. Regional variation of
SrPb isotopic compositions for
mafic-intermediate rocks (SiO
,56 wt%)
from the Aeolian arc. Alicudi and Filicudi
andesites (SiO
¼5662%) are also
plotted, since these represent the least
contaminated magmas in the Aeolian arc
(see text). Data of Marsili seamount are
shown as a dashed line on the left-hand side
of the diagrams. Source of data as in
Figure 15.2.
along-arc variation of some ITE ratios is reported in Figure 15.9.
The predominant features observed on diagrams are as follows.
(1) There is an evident increase of Rb/Nb and several other
LILE/HFSE ratios (e.g. La/Nb, Ba/Nb, U/Nb and, to a
lesser extent, Rb/Ta) from the marginal islands of Alicudi
and Stromboli to the central islands, where a large scattering
is observed for Vulcano.
(2) LILE/LILE ratios also show considerable variation along the
arc. For instance, Ce/Pb decreases eastwards and exhibits a
large scattering at Lipari. Sr/Nd and Sr/Th (not shown)
ratios are lower at the arc margins, especially at Stromboli,
than in the central islands (Fig. 15.9c). Ba/La increases
from Alicudi to Filicudi and other central islands, reaching
a maximum at Stromboli which also shows a large range of
values (Fig. 15.9d).
(3) HFSE/HFSE ratios Nb/Zr (Fig. 15.9e), Zr/Ti and, to a lesser
extent, Nb/Ta (not shown) decrease from marginal to central
islands. Nb and Zr abundances, but also LREE abundances
and La/Yb ratios, show the same type of distribution (not
(4) Th/LREE ratios (Fig. 15.9f) remain fairly constant in the CA
rocks of the western-central arc and increase in the Vulcano
shoshonitic rocks and at Stromboli.
(5) The Marsili volcano, sited in a back-arc position NW of the
Aeolian archipelago, shows a wide range of compositions but
is close to the western island of Alicudi for many ITE ratios.
Most trace element ratios of Figure 15.9 are not affected by frac-
tional crystallization since they are equally incompatible in the
main igneous rock minerals. Also, they do not show significant
correlation with Sr isotopes in the contaminated Alicudi and
Primordial Vulcano mafic suites. It is therefore reasonable to con-
clude that the observed along-arc variations reflect a compositional
zoning of the mantle source. Understanding the processes that gen-
erated these variations is crucial for clarifying key aspects of the
Aeolian subduction factory.
Mantle metasomatism
At least three different end-members are considered to have con-
tributed to the source composition of the Aeolian magmas.
These include the pre-metasomatic mantle, the Ionian subducted
crust and the Ionian Sea sediments. The composition of each end-
member is internally variable and poorly known. The upper mantle
beneath the southern Tyrrhenian Sea has a mid-ocean-ridge basalt
(MORB-) to OIB-type composition, based on geochemistry of
magmas erupted in and around the Tyrrhenian Sea basin (Trua
et al. 2004, 2011). Subducted Ionian crust has been hypothesized
to have an oceanic to thinned continental character, and a lateral
variation in composition has been suggested (Doglioni et al.
2001). Sediments are abundant on the Ionian seafloor, but inade-
quately characterized compositionally. For this reason, a geochem-
ical study of Ionian sediments has been undertaken and
preliminary data are reported as a spider-diagram in Figure 15.5d.
The concomitant increase of Sr- and decrease of Nd-isotope
ratios from the western to eastern Aeolian arc have been inter-
preted as evidence for eastwards increasing contamination of the
mantle source by subducted upper crustal material, likely
Etna basalts Ionian sediments Tyrrhenian MORB
West East West East
Lipari Vulcano
Fig. 15.9. Regional variation of trace
element ratios for the newly analysed
Aeolian samples (Table 15.1). Average
compositions of Tyrrhenian MORB
(Dietrich et al. 1977), Etna (Viccaro &
Cristofolini 2008) and Ionian sediments (De
Astis, unpublished data) are also reported.
sediments (e.g. Ellam et al. 1988, 1989; Francalanci et al. 1993,
2004, 2007; De Astis et al. 2000; Peccerillo 2005). The new ana-
lyses of Ionian sediments show Sr concentrations of c. 200 ppm
Sr of c. 0.711. Assuming a bulk mixing between a
primordial-type mantle and such sediments, an addition of less
than 2% contaminant is sufficient to explain the entire range of iso-
topic variation along the western-central Aeolian arc (Fig. 15.7).
Much higher amounts of c. 4 10% are necessary to explain the
composition of the Stromboli mantle sources. These are
maximum values because shallow-level magma contamination
likely contributed to increase Sr isotope ratios of Aeolian
magmas, including the mafic magmas. Moreover, bulk mixing is
not a viable mechanism of mantle contamination, and hydrous
fluid or melts from sediments have been suggested as the likely
carriers of incompatible elements into the mantle wedge
(Hermann & Rubatto 2009). These are much richer in Sr than
the source rocks because of low solid/fluid partition coefficients
for Sr at high pressures (Hermann & Rubatto 2009). This consider-
ably decreases the amount of contaminant that would be necessary
to explain the Sr-isotope ratios observed along the arc. For
instance, if a melt formed by 30 50% sediment melting is
assumed as metasomatic agent, Sr concentration in the melt
would be 2 3 times higher than the source rock. This reduces
the amount of mantle contaminant by a factor of 2 3, and less
than 1% melted sediment is sufficient to explain Sr-isotope ratios
of the western-central arc and only 2 5% would be needed at
In conclusion, two types of metasomatic agents, likely fluids, are
suggested by Sr-isotope modelling in the Aeolian arc. One type of
fluid, operating in the western-central arc, had low Sr isotope ratios
and was likely released from an oceanic slab with little or no sedi-
ment involvement. Another fluid was enriched in radiogenic Sr and
requires an important contribution from sediments in the eastern
sector of the arc. Following Hermann & Rubatto (2009), the
term ‘fluid’ is used here in its broadest sense, that is, to indicate
aqueous fluids (water-rich fluid containing low amount of
solute), H
O-rich silicate melts and supercritical H
fluids (intermediate between the two).
The hypothesis of two compositionally distinct metasomatic
fluids is supported by incompatible trace element ratios such as
Ba/La, Th/Sr, Th/Pb, Th/U, Ba/La, Ti/Zr and Sr/Nd, which
all show diverging trends for Stromboli and for the central-western
islands (e.g. De Astis et al. 2000). Variations for some of these
ratios are reported in Figure 15.10
The nature of metasomatic fluids and the efficiency of element
transfer from slab to the mantle wedge is controversial. This is
true not only for the Aeolian arc, but for subduction magmatism
at a global scale (Brenan et al. 1995; Elliot et al. 1997; Becker
et al. 2000; Kessel et al. 2005; Hermann & Rubatto 2009).
Investigation of MORB-type rocks (Kessel et al. 2005) demon-
strated that the capacity of elemental transport increases with
increasing temperature and pressure from aqueous fluids to
supercritical fluids and melts. LILE/LILE ratios such as Rb/Sr,
Ba/La and Ba/Rb are more easily fractionated by aqueous fluids
than by high-temperature supercritical fluids and melts.
However, hydrous melts and supercritical fluids more efficiently
fractionate other element ratios such as Sr/REE and La/Yb.
LILE/HFSE are fractionated by all types of fluids, but low-
temperature aqueous fluids are less able to transfer large
amounts of trace elements than high-temperature supercritical
fluids and melts. High LILE/HFSE ratios coupled with low ITE
abundances (e.g. Th) have therefore been suggested as useful cri-
teria to recognize aqueous fluid metasomatic modifications (Kessel
et al. 2005).
Hermann & Rubatto (2009) suggested that subducted sediments
are the most important sources of incompatible elements for meta-
somatic fluids in subduction zones. The involvement of sediments
in the subduction processes considerably complicates the process
of slab to mantle element transfer however, due to the possible
occurrence of a large variety of major and accessory residual
phases such as phengite, rutile, allanite/monazite and zircon.
Their stability or breakdown at various pressure/temperature (P/
T) conditions influences the composition of fluids emitted from
the slab and hence the flux of incompatible trace elements into
the overlying mantle wedge. For instance, two- to five-fold Ba/
La variations can be generated in melted sediments and transferred
to the mantle wedge from these, depending on the occurrence or
absence of phengite and monazite in the residue. Note that high
Ba/La is traditionally considered a typical signature of low-
temperature metasomatic aqueous fluids (Brenan et al. 1995;
Elliott et al. 1997).
The intrinsic complexities of element transfer from slab to
mantle wedge, along with the poorly known compositions of end-
members involved in the Aeolian subduction processes, make it
difficult to understand mechanisms of element mobilization and
the contribution of various components to mantle wedge compo-
sition. This has fed much speculation and debate; for example,
Tonarini et al. (2004) suggested an increase of both aqueous
fluid flow and sediment input from west to the east, on the basis
of an eastwards increase of B/Nb and d
B of lavas. This is sup-
ported by an eastwards decrease of Ce/Pb, typical of aqueous
fluids, and an increase in Th/La, which is high in the sediments
(Fig. 15.9f). However, LILE/HFSE show a decrease from
central arc to Stromboli, that is, the opposite to that expected for
aqueous fluid metasomatism.
Francalanci et al. (1993, 2007) argued that an increase of LILE/
HFSE from external to central islands was related to a stronger role
of metasomatism by aqueous fluids in the central arc. However,
this idea only holds if a homogeneous composition of pre-
metasomatic mantle wedge is assumed for LILE/HFSE. More-
over, high mobile/immobile element ratios (e.g. Rb/Th) should
be coupled with low immobile element (e.g. Th) enrichments
(Kessel et al. 2005). This is not observed in the central Aeolian
arc, except perhaps at Salina. Finally, variations of HFSE/HFSE
Etna basalts Ionian sediments Tyrrhenian MORB
10 20 30 40
10 30
(a)(b)Fig. 15.10. Ba/La, Sr/Nd and
variation diagrams for the newly analysed
rocks. Sr isotope data are from the literature
(source of data as in Fig. 15.2) and have been
determined either on the same rocks
analysed in this study or on different rock
samples from the same outcrops.
Composition of the Tyrrhenian MORB,
Etna and Ionian sediments are also reported.
Arrows indicate effects of metasomatic
fluids derived from oceanic crust (grey
arrow) and from sediments (white arrow).
Symbols as in Figure 15.4.
ratios (Fig. 15.9e) are also difficult to explain, in that this group of
elements is immobile during aqueous fluid transfer. Therefore,
aqueous fluid transfer may have been present in the central
Aeolian arc, but it cannot be the only process responsible for the
observed trace element variations.
Many of the issues mentioned above are overcome if a hetero-
geneous OIB- to MORB-type starting mantle composition is
assumed for the Aeolian arc (Ellam et al. 1988). An OIB-type com-
ponent under the external islands could explain enrichment in Nb
and LREE, as well as the relatively high Nb/Zr and low Rb/Nb
and Sr/Nd ratios. By contrast, a MORB-type composition for
the central arc better explains the low Nb/Zr and Zr/Ti.
However, several issues still remain unresolved. For instance,
variations of Ba/La (Fig. 15.10) cannot result from any shallow-
level magmatic evolution process. By contrast, Sr/Nd ratios
can change during crystal fractionation if plagioclase is involved;
however, the positive correlation with Ba/La in the western-
central islands excludes this possibility (Fig. 15.10a). The covari-
ation of Ba/La and Sr/Nd in the central-western arc is therefore
a reproduction of source heterogeneity, and can be attributed to
metasomatic fluids from an oceanic slab (grey arrows in
Fig. 15.10). The slight positive trend between Sr/Nd and
Sr could indicate modest sediment involvement, but
might also reflect a variably altered oceanic crust as source of
fluids. Positive correlation between Ba/La and
Sr at Strom-
boli fits well with the hypothesis of metasomatism by low-
temperature (about 700 800 8C) hydrous melts from sediments
(white arrows in Fig. 15.10), which have high Ba/La because of
residual LREE-rich accessory phases (Hermann & Rubatto
2009). However, experimental data clearly show that these melts
also have high Sr/Nd, and a positive correlation between the
two ratios should be observed. Instead, the almost flat trend for
Stromboli rocks (Fig. 15.10a) requires a selective Ba enrichment
that increases Ba/La but not Sr/Nd and other ITE ratios. Tomma-
sini et al. (2007) suggested a two-stage enrichment process for the
Stromboli mantle an hypothesis supported by Schiavi et al. (2012)
on the basis of trace element and Pb-B-Li isotope data on melt
inclusions. Early high-P/T supercritical fluids from basalts and
sediments produced a general enrichment in all lithophile
elements, with little element fractionation. An aqueous fluid at
lower P/T selectively enriched the mantle wedge in Ba (see Fran-
calanci et al. 2013). However, other element ratios that are strongly
affected by fluid transport (e.g. U/Nb, Rb/Th, U/Ta, U/Th, etc.)
should be correlated with Ba/La, a feature that is not observed in
the Stromboli rocks.
Conditions of mantle melting and the origin of calc-alkaline and
shoshonitic magmas
The distribution of calc-alkaline and shoshonitic magmas in space
and time has received considerably less attention in the literature
than trace elements and isotope geochemistry. Calc-alkaline rocks
have comparable composition as shoshonites for several major
and trace elements (Fig. 15.3), but shoshonites have higher con-
centrations of K, P and all incompatible trace elements. Some
shoshonites are undersaturated in silica, with up to 10% of nor-
mative nepheline, whereas calc-alkaline rocks are saturated to
oversaturated in silica. These differences can depend either on a
heterogeneous source and/or on variable degrees and physico-
chemical conditions of partial melting.
REE geochemistry can help to clarify this issue. Light REE frac-
tionation (i.e. La/Sm) of primary magmas depends on the degree
of melting and/or on the La enrichment of the source. Heavy
REE (HREE) fractionation (i.e. Tb/Yb) depends essentially on
the presence or absence of residual garnet during mantle
melting. Garnet is a high-pressure mantle mineral that retains
HREE with respect to the light and mid REE. Its occurrence as
residual phase during partial melting therefore results in high
Tb/Yb (and La/Yb) in the magmas. La/Sm increases slightly
with magma evolution; only mafic rocks should therefore be con-
sidered for constraining source processes.
The La/Sm v. K
O diagram for the most mafic among the ana-
lysed rocks (MgO .4 wt%) shows that Filicudi, Salina and
Lipari have similar La/Sm ratios, but higher values are observed
at Alicudi and in some CA samples from Stromboli (Fig. 15.11a).
Since all these rocks have the same petrological characteristics, it
is reasonable to assume an origin by comparable degrees of
mantle melting. Higher La/Sm ratios in the CA rocks of the
two external islands therefore point to a stronger enrichment of
LREE in their mantle sources. At Vulcano, there is an increase
of La/Sm from CA to SHO rocks at fairly constant Sr-isotope
ratio (De Astis et al. 1997). By contrast, La/Sm ratios do not
change significantly from CA to SHO rocks at Stromboli,
Sr ratios increase strongly (Francalanci et al.
1988). These data suggest that HKCA and SHO magmas at
Vulcano could be related to variable degrees of partial melting
of a homogeneous source, whereas CA and SHO magmas at
Stromboli are generated by similar degrees of partial melting of
a isotopically heterogeneous source that was variably contami-
nated by subducted sediments. The obvious conclusion is that
SHO magmas are generated by different processes in the
Aeolian arc as already suggested by Ellam et al. (1988) and De
Astis et al. (2000). Finally, Tb/Yb ratios are generally high in
all shoshonites. This points to the occurrence of residual garnet
in the source during melting and, hence, to a deeper origin for
SHO than the associated CA magmas.
The physical conditions that generated variable degrees of
melting for CA and SHO magmas in the central Aeolian arc are
of interest for petrology and geodynamics. It is well known that
water is crucial to promote partial melting in the subduction
environments (e.g. Ulmer 2001; Grove et al. 2012). Variable
degrees of melting in the Aeolian arc could therefore be related
to different fluxes of water from the slab. These were higher
MgO > 4%
0 1 2 3 4 5
0 1 2 3 4 5
K2O wt% K2O wt%
Fig. 15.11. La/Sm and Tb/Yb v. K
diagrams for the most mafic among the
analysed samples (MgO .4 wt%). Plots
are restricted to mafic compositions to
minimize effects of La/Sm variation related
to fractional crystallization. For further
explanation see text. Symbols as in
Figure 15.4.
during calc-alkaline magma activity, and were less abundant in
the zones and times of shoshonitic magma formation. Variable
water fluxes could be tentatively attributed to different stages of
subduction process. Noting that shoshonitic magmas appear
during mature to late stages of volcanism, it is reasonable to pos-
tulate a decrease of water flux with time.
Pre-metasomatic mantle composition
Gaining insight into the original composition of the upper mantle
beneath the Aeolian Islands is difficult, due to extensive modifi-
cation produced by metasomatic processes. This is however an
important step to a better understanding of mantle source evolution
and geodynamic setting in the southern Tyrrhenian Sea. Ellam
et al. (1988) hypothesized an OIB- to MORB-type composition
for pre-metasomatic mantle, and suggested that HFSE enrichment
in some islands was evidence for the occurrence of the OIB com-
ponent in the sub-arc mantle. Such a hypothesis also explains the
linear Pb-isotope arrays between the Calabro Peloritano base-
ment and the OIB-type Etna volcano (Fig. 15.6b), which suggest
contamination of an OIB-type source by subducted crustal
material. By contrast, Francalanci et al. (2007) and Tommasini
et al. (2007) envisage a homogeneous MORB-type pre-
metasomatic mantle along the entire arc, and explain the regional
geochemical and isotopic variations as entirely related to variable
roles of aqueous and supercritical fluids or melts from an altered
oceanic crust and associated sediments. Accordingly, radiogenic
Pb-isotope signatures observed in some islands were explained
as the result of metasomatism by fluids released from sediments
and aged Ionian oceanic crust.
The data and discussion presented in this paper support the
hypothesis of a zoned OIB- to MORB-type pre-metasomatic
mantle for the Aeolian arc. In particular, an OIB-type component
in the marginal islands would explain both high HFSE contents and
LREE abundances and fractionation. Variable HFSE ratios are also
better explained by pre-metasomatic mantle heterogeneities, since
these elements behave as immobile during metasomatism.
Francalanci et al. (2007) argued that the OIB-type nature of the
external islands conflicts with the low Pb-isotope ratios of Alicudi
and Stromboli, as compared to those of the central island of Salina.
However, relatively unradiogenic Pb compositions at Stromboli
are an effect of contamination of the mantle source by sediments,
which completely altered its original Pb-isotope signature. A
decrease of
Pb ratios from Salina to Alicudi is only
observed if the Alicudi basalts are considered as the most primitive
compositions in the island. However, it has long been demon-
strated that the Alicudi basalts are more contaminated than the
associated andesites (Peccerillo & Wu 1992; Lucchi et al.
2013a). Therefore, if more evolved but uncontaminated andesites
are considered, Pb-isotopic values at Alicudi are similar to those at
Geodynamic implications
There are important relationships between magma and mantle
compositions and the geodynamic setting of the Aeolian arc. The
diversity of the mantle contamination processes in the western-
central and eastern sectors suggests a different nature for the
subducted material. A basaltic slab, with little or no sediment invol-
vement, is indicated by geochemical data as a source of metaso-
matic fluids in the western-central islands, whereas an important
contribution by subducted sediments or other upper crustal
materials is required for metasomatism at Stromboli. The
Tindari Letojanni Fault therefore represents the boundary that
divides two distinct compositions of the subducted material. Such
a conclusion is also suggested by Doglioni et al. (2001), although
these authors propose a continental-type crust in the west and an
oceanic-type crust in the east, a conclusion that strongly contrasts
with radiogenic isotope signatures of the Aeolian magmas.
Metasomatic fluids activated extensive modification of the
upper mantle beneath the Aeolian volcanic arc. However, some
geochemical signatures of the pre-metasomatic mantle were pre-
served, and indicate a depleted MORB-type source in the central
sector and a more fertile OIB-type component for the external
Peccerillo (2001) argued that the OIB-type component at Strom-
boli could have originated by inflow of asthenospheric mantle from
the Africa foreland around the margins of the retreating slab. Trua
et al. (2004, 2011) envisaged the same type of process to explain
the occurrence of MORB and OIB components at Marsili. Franca-
lanci et al. (2007) and Tommasini et al. (2007) consider the
hypothesis of mantle flow as unrealistic, a statement that does
not take into account the particular geodynamic setting of the
Aeolian arc. Here, a narrow Ionian slab is subducting beneath
the southern Tyrrhenian Sea (Fig. 15.12) and is retreating toward
the SE (Gvirtzman & Nur 1999), generating deep seismic activity
beneath the eastern Aeolian arc. In contrast, deep seismicity is
lacking beneath the western Aeolian arc, a feature that could be
related to collision and slab break-off in this sector where a frag-
ment of oceanic slab is suggested to passively sink into the
upper mantle (see Peccerillo 2005; Panza et al. 2007 for further
It is well known that the Benioff zone rollback requires mantle
flow to replace the space left by the retreating slab. Such a replace-
ment can occur by mantle flow from the back-arc area. However,
for a narrow slab such as that in the southern Tyrrhenian Sea
most of the asthenospheric inflow likely occurs from the foreland,
moving around the margins of the retreating slab (Fig. 15.12). The
mantle sources at the margins of the slab are therefore the most
heavily affected by inflow and consequently show the clearest evi-
dence of OIB-type components. It should be recalled that all vol-
canoes situated on the margin of the African plate (e.g. Etna,
Iblei, Linosa, etc.) have an OIB-type composition.
Fig. 15.12. Schematic geodynamic setting of the Aeolian arc. A narrow Ionian
plate is subducting beneath Calabria and the southern Tyrrhenian Sea. This is
associated with deep seismicity and active volcanism, and is bounded to the
west by the Tintari Letojanni Fault (TLF) system. A detached and passively
sinking oceanic slab is envisaged for the western Aeolian arc. Curved black
arrows indicate asthenospheric mantle inflow from the foreland around the
margins of the subducted slabs. Collision zones are indicated with a dashed line.
For further explanation, see text.
The overall petrological and geochemical features of the Aeolian
arc and the relationships with petrogenesis and geodynamics can
be summarized as follows.
(1) CA and HKCA rocks make up all the western islands and the
largest part of Lipari and Panarea, whereas HKCA and SHO
rocks are dominant at Vulcano and Stromboli. Shoshonitic
rocks from these islands have similar compositions for
many major and many trace elements, but exhibit strong
differences for radiogenic isotopes (Sr Nd Pb) and some
trace element abundances and ratios. This suggests that
shoshonitic magmatism in the Aeolian arc is polygenetic. In
particular, decreasing degrees of partial melting of a homo-
geneous source at various depths generated the transition
from high-K calc-alkaline to shoshonitic magmatism at
Vulcano. At Stromboli, calc-alkaline and shoshonitic mag-
mas are related to polybaric melting of heterogeneous man-
tle sources that were variably contaminated by subducted
(2) There are distinct Sr-, Nd- and Pb-isotope signatures in
different sectors of the arc. Some incompatible trace
element ratios also show diverging variation trends. Differ-
ent types of mantle metasomatic processes have been respon-
sible for these features. Metasomatic fluids affecting the
western-central arc originated from a subducted basaltic
crust, whereas upper crustal material (likely oceanic-type
crust plus sediments) was a main source of metasomatic
fluids under Stromboli.
(3) Modification by metasomatic fluids was superimposed on a
heterogeneous OIB- to MORB-type pre-metasomatic
mantle wedge. An OIB-type component in the source is
recognized for the external islands of Alicudi and Stromboli
and for the Marsili seamount, but not in the central Aeolian
arc where a depleted MORB-type mantle composition is
suggested by rock chemistry. The OIB-type component
was provided by asthenospheric inflow from the Africa fore-
land, around the edges of the slab during rollback.
(4) Aeolian arc magmas were affected by complex evolution
processes which drove parental basalts towards intermediate
and acidic compositions. The degree of magma evolution
was much more extensive in the central islands of Lipari
and Vulcano, where abundant rhyolites were erupted
during the latest activity stages. This is related to the trans-
tensional tectonics along the Tindari Letojanni transfer
fault, which favoured the formation of large intra-crustal
magma chambers where magmas ponded and fractionated
for a long time to give abundant rhyolitic melts.
(5) Geobarometric investigations revealed polybaric magma
evolution processes for the Aeolian volcanoes. Early basaltic
activity, which characterized the lowest exposed sequences
on most islands, was fed by deep magma chambers in
which magmatic evolution was dominated by fractional crys-
tallization and assimilation plus continuous mixing with
fresh mafic melts from the source. Younger andesitic and
rhyolitic activity was fed by shallower magma chambers,
where magmatic evolution was dominated by fractional crys-
tallization. An overall upwards migration for magma
chambers of the Aeolian volcanoes is therefore suggested
by geobarometric investigations.
Research on Aeolian orogenic magmatism has been financed by MIUR,
PRIN2008. The authors thank J. Hermann, ANU, R. Harmon and an anonymous
referee for constructive reviews.
Barberi, F., Gandino,A.,Gioncada,A.,La Torre, P., Sbrana,A.&
Zenucchini, C. 1994. The deep structure of the Aeolian arc in the
light of gravity, magnetic and volcanological data. Journal of Volca-
nology and Geothermal Research,61, 189 206.
Barker, D. S. 1987. Rhyolites contaminated with metapelite and gabbro,
Lipari, Aeolian Islands, Italy: products of lower crustal fusion or of
assimilation plus fractional crystallization? Contribution to Mineral-
ogy and Petrology,97, 460472.
Becker,H.,Jochum,K.P.&Carlson, R. W. 2000. Trace element frac-
tionation during dehydration of eclogites from high-pressure terranes
and the implications for element fluxes in subduction zones. Chemical
Geology,163, 6599.
Brenan,J.M.,Shaw,H.F.,Ryerson,F.J.&Phinney, D. L. 1995.
Mineral– aqueous fluid partitioning of trace elements at 900 8Cand
2 GPa: constraints on the trace element chemistry of mantle and deep
crustal fluids. Geochimica et Cosmochimica Acta,59, 3331 –3350.
et al
. 2002. Petrology and geochemistry
of the Island of Panarea: implicationsfor mantle evolution beneath the
Aeolian island arc (Southern Tyrrhenian Sea, Italy). Journal of Volca-
nology and Geothermal Research,115, 367 395.
Crisci,G.M.,De Rosa, R., Esperanc¸a, S., Mazzuoli,R.&Sonnino,
M. 1991. Temporal evolution of a three component system: the island
of Lipari (Aeolian Arc, southern Italy). Bulletin of Volcanology,53,
207 221.
`,M.,Behrens,H.,Vetere,F.&De Rosa, R. 2008. The viscosity of
latitic melts from Lipari (Aeolian Islands, Italy): inference on mixing–
mingling processes in magmas. Chemical Geology,259,89–97.
De Astis,G.,La Volpe, L., Peccerillo,A.&Civetta, L. 1997. Volca-
nological and petrological evolution of Vulcano Island (Aeolian Arc,
southern Tyrrhenian Sea). Journal of Geophysical Research,102,
8021 8050.
De Astis, G., Peccerillo,A.,Kempton, P. D., La Volpe,L.&Wu ,
T. W. 2000. Transition from calc-alkaline to potassium-rich mag-
matism in subduction environments: geochemical and Sr, Nd, Pb
isotopic constraints from the Island of Vulcano (Aeolian arc). Contri-
butions of Mineralogy and Petrology,139, 684 703.
De Astis,G.,Lucchi, F., Dellino, P., La Volpe, L., Tranne,C.A.,
Frezzotti,M.L.&Peccerillo, A. 2013. Geology, volcanic
history and petrology of Vulcano (central Aeolian archipelago). In:
Lucchi, F., Peccerillo,A.,Keller, J., Tranne,C.A.&Rossi,
P. L. (eds) The Aeolian Islands Volcanoes. Geological Society,
London, Memoirs, 37, 281348.
De Rosa,R.&Sheridan, M. F. 1983. Evidence for magma mixing in the
surge deposits of the Monte Guardia sequence, Lipari. Journal of Vol-
canology and Geothermal Research,17, 313 328.
Di Martino, C., Frezzotti, M. L., Lucchi, F., Peccerillo,A.,Tranne,
C. A. & Diamond, L. W. 2010. Magma storage and ascent at Lipari
Island (Aeolian archipelago, southern Italy) during the old stages
(223– 81 ka): role of crustal processes and tectonic influence. Bulletin
of Volcanology,72, 1061 1076.
Di Martino, C., Forni,F.
et al
. 2011. Formation of cordierite-bearing
lavas during anatexis in the lower crust beneath Lipari Island
(Aeolian arc, Italy). Contribution to Mineralogy and Petrology,
162, 10111030.
Dietrich, V., Emmermann, R., Keller,J.&Puchelt, H. 1977. Tholeii-
tic basalts from the Tyrrhenian Sea floor. Earth and Planetary
Science Letters,36, 285 296.
Doglioni, C., Innocenti,F.&Mariotti, G. 2001. Why Mt. Etna? Terra
Nova,13, 25 31.
Ellam,R.M.&Harmon, R. S. 1990. Oxygen isotope constraints on the
crustal contribution to the subduction-related magmatism of the
Aeolian Islands, southern Italy. Journal of Volcanology and Geother-
mal Research,44, 105122.
Ellam,R.M.,Menzies,M.A.,Hawkesworth, C. J., Leeman, W. P.,
Rosi,M.&Serri, G. 1988. The transition from calc-alkaline to potas-
sic orogenic magmatism in the Aeolian Islands, Southern Italy. Bul-
letin of Volcanology,50, 386398.
Ellam,R.M.,Hawkesworth, C. J., Menzies,M.A.&Rogers,N.W.
1989. The volcanism of Southern Italy: role of subducion and the
relationships between potassic and sodic alkaline magmatism.
Journal of Geophysical Research,94, 45894601.
Elliott, T., Plank, T., Zindler,A.,White,W.&Bourdon, B. 1997.
Element transport from slab to volcanic front at the Mariana arc.
Journal of Geophysical Research,102, 1499115019.
Esperanc¸a, S., Crisci,G.M.,De Rosa,R.&Mazzuoli, R. 1992. The
role of the crust in the magmatic evolution of the Island of Lipari
(Aeolian Islands, Italy). Contributions to Mineralogy and Petrology,
112, 450462.
Forni, F., Lucchi, F., Peccerillo, A., Tranne,C.A.,Rossi,P.L.&
Frezzotti, M. L. 2013. Stratigraphy and geological evolution of
the Lipari volcanic complex (central Aeolian archipelago). In:
Lucchi, F., Peccerillo,A.,Keller, J., Tranne,C.A.&Rossi,
P. L. (eds) The Aeolian Islands Volcanoes. Geological Society,
London, Memoirs, 37, 213280.
Francalanci, L., Barbieri,M.,Manetti, P., Peccerillo,A.&
Tolomeo, L. 1988. Sr isotopic systematics in volcanic rocks from
the Island of Stromboli, Aeolian arc (Italy). Chemical Geology
(Isotope Geoscience Section),73, 109 124.
Francalanci, L., Manetti,P.&Peccerillo, A. 1989. Volcanological
and magmatological evolution of Stromboli volcano (Aeolian
Islands): the roles of fractional crystallization, magma mixing,
crustal contamination, and source heterogeneity. Bulletin of Volca-
nology,51, 355378.
Francalanci, L., Taylor, S. R., Mcculloch,M.T.&Woolhead,J.D.
1993. Geochemical and isotopic variations in the calc-alkaline
rocks of Aeolian arc, southern Tyrrhenian Sea, Italy: constraints on
magma genesis. Contributions to Mineralogy and Petrology,113,
300 313.
Francalanci, L., Avanzinelli, R., Petrone,C.M.&Santo, A. 2004.
Petrochemical and magmatological characteristics of the Aeolian Arc
volcanoes, southern Tyrrhenian Sea, Italy: inferences on shallow
level processes and magma source variations. Periodico di Mineralo-
gia,73, 75104.
Francalanci, L., Avanzinelli, R., Tommasini,S.&Heuman, A. 2007.
A west-east geochemical and isotopic traverse along the volcanism of
the Aeolian Island arc, southern Tyrrhenian Sea, Italy: interferences
on mantle source processes. Geological Society of America Special
Papers,418, 235 263.
Francalanci, L., Lucchi, F., Keller, J., De Astis,G.&Tranne,C.A.
2013. Eruptive, volcano-tectonic and magmatic history of the Strom-
boli volcano (north-eastern Aeolian archipelago). In:Lucchi, F.,
Peccerillo,A.,Keller, J., Tranne,C.A.&Rossi, P. L. (eds)
The Aeolian Islands Volcanoes. Geological Society of London,
Memoirs, 37, 395470.
Frezzotti,M.L.&Peccerillo, A. 2004. Fluid inclusion and petrologi-
cal studies elucidate reconstruction of magma conduits. Transactions
of the American Geophysical Union,85, 157.
Frezzotti, M. L., Peccerillo,A.&Bonelli, R. 2003. Magma ascent
rates and depths of magma reservoirs beneath the Aeolian volcanic
arc (Italy): inferences from fluid and melt inclusions in crustal xeno-
liths. In:Bodnar,B.&De Vivo, B. (eds) Melt Inclusions in Volcanic
Systems. Elsevier, Amsterdam, 185 206.
Frezzotti, M. L., Peccerillo,A.,Zanon,V.&Nikogosian, I. 2004.
Silica-rich melts in quartz xenoliths from Vulcano island and
their bearing on process of crustal anatexis and crust-magma inter-
action beneath the Aeolian arc, southern Italy. Journal of Petrology,
45, 3 26.
Gertisser,R.&Keller, J. 2000. From basalt to dacite: origin and evol-
ution of the calc-alkaline series of Salina, Aeolian Arc, Italy. Contri-
butions to Mineralogy and Petrology,139, 607 626.
Gillot, P. Y. 1987. Histoire volcanique des Iles Eoliennes: arc insulaire
ou complexe oroge
´nique anulaire? Documents et Travaux, Institut
´ologique Albert-de-Lapparent, Paris, 11, 3542.
Gioncada,A.,Mazzuoli, R., Bisson,M.&Pareschi, M. T. 2003. Pet-
rology of volcanic products younger than 42 ka on the Lipari-Vulcano
complex (Aeolian Islands, Italy): an example of volcanism controlled
by tectonics. Journal of Volcanology and Geothermal Research,122,
191 220.
Gioncada,A.,Mazzuoli,R.&Milton, A. J. 2005. Magma mixing at
Lipari (Aeolian Islands, Italy): insights from textural and compo-
sitional features of phenocrysts. Journal of Volcanology and Geother-
mal Research,145, 97118.
Grasso, M. 2001. The Apenninic-Maghrebian orogen in Southern Italy,
Sicily and adjacent areas. In:Va i ,G.B.&Martini, P. I. (eds)
Anatomy of an Orogen. The Apennines and adjacent Mediterranean
basins. Kluwer, Dordrecht, 255 286.
Grove, T. L., Till,C.B.&Krawczynsky, M. J. 2012. The role of H
in subduction-zone magmatism. Annual Review of Earth and Plane-
tary Science,40, 413439.
Gvirtzman,Z.&Nur, A. 1999. The formation of Mount Etna as the con-
sequence of slab rollback. Nature,401, 782 785.
Hart, S. R. 1984. A large-scale isotope anomaly in the Southern Hemi-
sphere mantle. Nature,309, 753 757.
Hart, S. R., Hauri, E. H., Oschmann,L.A.&Whitehead, J. A. 1992.
Mantle plumes and entrainment—Isotopic evidence. Science,256,
Hermann,J.&Rubatto, D. 2009. Accessory phase control on trace
element signature of sediment melt in subduction zones. Chemical
Geology,265, 512526.
Keller, J. 1982. The Mediterranean island arc. In:Thorpe, R. S. (ed.)
Andesites: Orogenic Andesites and Related Rocks. Wiley, Chichester,
Kessel, R., Schmidt,M.W.,Ulmer,P.&Pettke, T. 2005. Trace
element signatures of subduction-zone fluids, melts and supercritical
liquids at 120 180 km depth. Nature,437, 724 727.
Leocat, E. 2011. Histoire eruptive des volcans du secteur occidental des
Iles Eoliennes (Sud de la Mer Tyrrhenienne, Italie).PhD thesis, Uni-
versity of Paris Sud, Orsay.
Lucchi, F., Peccerillo,A.,Tranne,C.A.,Rossi, P. L., Frezzotti,
M. L. & Donati, C. 2013a. Volcanism, calderas and magmas of
the Alicudi composite volcano (western Aeolian archipelago). In:
Lucchi, F., Peccerillo, A., Keller, J., Tranne,C.A.&Rossi,
P. L. (eds) The Aeolian Islands Volcanoes. Geological Society,
London, Memoirs, 37, 83112.
Lucchi, F., Santo, A. P., Tranne,C.A.,Peccerillo,A.&Keller,J.
2013b. Volcanism, magmatism, volcano-tectonics and sea-level fluc-
tuations in the geological history of Filicudi (western Aeolian archi-
pelago). In:Lucchi, F., Peccerillo, A., Keller, J., Tranne,C.A.
&Rossi, P. L. (eds) The Aeolian Islands Volcanoes. Geological
Society, London, Memoirs, 37, 113 154.
Lucchi, F., Gertisser, R., Keller, J., Forni, F., De Astis,G.&
Tranne, C. A. 2013c. Eruptive history and magmatic evolution of
the Island of Salina (central Aeolian archipelago). In:Lucchi, F.,
Peccerillo,A.,Keller, J., Tranne,C.A.&Rossi, P. L. (eds)
The Aeolian Islands Volcanoes. Geological Society, London,
Memoirs, 37, 155212.
Lucchi, F., Tranne,C.A.,Peccerillo, A., Keller,J.&Rossi,P.L.
2013d. Geological history of the Panarea volcanic group (eastern
Aeolian archipelago). In:Lucchi, F., Peccerillo,A.,Keller, J.,
Tranne,C.A.&Rossi, P. L. (eds) The Aeolian Islands Volcanoes.
Geological Society, London, Memoirs, 37, 349 394.
Martelli,M.,Nuccio,P.M.,Stuart,F.M.,Di Liberto,V.&Ellam,
R. M. 2008. Constraints on mantle source and interactions from
He-Sr isotope variation in Italian Plio-Quaternary volcanism. Geo-
chemistry, Geophysics, Geosystems,9, Q02001, doi: 10.1029/
Nazzareni, S., Molin, G., Peccerillo,A.&Zanazzi, P. F. 1998.
Structural and chemical variations in clinopyroxenes from the
Island of Alicudi (Aeolian arc) and their implications for con-
ditions of crystallization. European Journal of Mineralogy,10,
Nazzareni, S., Molin,M.,Peccerillo,A.&Zanazzi, P. F. 2001. Vol-
canological implications of crystal chemical variations in clinopyrox-
enes from the Aeolian arc (Southern Tyrrhenian Sea, Italy). Bulletin
of Volcanology,63, 7382.
Nicolosi, I., Speranza,F.&Chiappini, M. 2006. Ultrafast oceanic
spreading of the Marsili basin, southern Tyrrhenian Sea: evidence
from magnetic anomaly analysis. Geology,34, 717 720.
O’hara, M. J. 1977. Geochemical evolution during fractional crys-
tallization of a periodically refilled magma chamber. Nature,266,
Panza, G. F., Pontevivo,A.,Chimera,G.,Raykova,R.&Aoudia,A.
2003. The lithosphere-asthenosphere: Italy and surroundings. Epi-
sodes,26, 169174.
Panza, G. F., Peccerillo,A.,Aoudia,A.&Farina, B. 2007. Geophy-
sical and petrological modelling of the upper mantle structure and
composition: the case of the Tyrrhenian Sea area. Earth Science
Reviews,80, 146.
Peccerillo, A. 2001. Geochemical similarities between the Vesuvius,
Phlegraean Fields and Stromboli volcanoes: petrogenetic, geody-
namic and volcanological implications. Mineralogy and Petrology,
73, 93105.
Peccerillo, A. 2005. Plio-Quaternary Volcanism in Italy. Petrology,
Geochemistry, Geodynamics. Springer, Heidelberg.
Peccerillo,A.&Taylor, S. R. 1976. Geochemistry of the Eocene
calc-alkaline volcanic rocks from the Kastamonu area, northern
Turkey. Contributions to Mineralogy and Petrology,58, 63 81.
Peccerillo,A.&Wu, T. W. 1992. Evolution of calc-alkaline magmas in
continental arc volcanoes: evidence from Alicudi, Aeolian Arc
(Southern Tyrrhenian Sea, Italy). Journal of Petrology,33,
1295 1315.
Peccerillo,A.,Kempton, P. D., Harmon, R. S., Wu,T.W.,Santo,A. P.,
Boyce,A.J.&Tripodo, A. 1993. Petrological and geochemical char-
acteristics of the Alicudi Volcano, Aeolian Island, Italy: implication
for magma genesis and evolution. Acta Vulcanologica,3, 235 249.
Peccerillo,A.,Dallai, L., Frezzotti,M.L.&Kempton, P. D. 2004.
Sr-Nd-Pb-O isotopic evidence for decreasing crustal contamination
with ongoing magma evolution at Alicudi volcano (Aeolian Arc,
Italy): implication for style of magma-crust interaction and mantle
source compositions. Lithos,78, 217233.
Peccerillo,A.,Frezzotti, M. L., De Astis,G.&Ventura, G. 2006.
Modeling the magma plumbing system of Vulcano (Aeolian
Islands, Italy) by integrated fluid-inclusion geobarometry, petrology
and geophysics. Geology,34, 1720.
Perugini,D.,Ventura,G.,Petrelli,M.&Poli, G. 2004. Kinematic
significance of morphological structures generated by mixing of
magmas: a case study from Salina Island (southern Italy). Earth
and Planetary Science Letters,222, 10511066.
Perugini,D.,Valentini,L.&Poli, G. 2007. Insights into Magma
Chamber Processes from the Analysis of Size Distribution of Enclaves
in Lava Flows: a Case Study from Vulcano Island (Southern Italy).
Journal of Volcanology and Geothermal Research,166, 193 203.
Petrelli,M.,Perugini,D.,Poli,G.&Peccerillo, A. 2007. Graphite
electrode lithium tetraborate fusion for trace element determination
in bulk geological samples by laser ablation ICP-MS. Microchimica
Acta,158, 275 282, doi: 10.1007/s00604-006-0731-6.
Petrelli,M.,Perugini, D., Alagna, K. E., Poli,G.&Peccerillo,A.
2008. Spatially resolved and bulk trace element analysis by laser abla-
tion – inductively coupled plasma – mass spectrometry (LA-ICP-
MS). Periodico di Mineralogia,77, 321.
Piochi,M.,De Astis, G., Petrelli,M.,Ventura, G., Sulpizio,R.&
Zanetti, A. 2009. Constraining the recent plumbing system of
Vulcano (Aeolian Arc, Italy) by textural, petrological, and fractal
analysis: the 1739 A.D. Pietre Cotte lava flow. Geochemistry, Geo-
physics, Geosystems,10, Q01009, doi: 10.1029/2008GC002176.
Rottura,A.,Del Moro,A.
et al
. 1991. Relationships between inter-
mediate and acidic rocks in orogenic granitoids suites: petrological,
geochemical and isotopic (Sr, Nd, Pb) data from Capo Vaticano
(southern Calabria, Italy). Chemical Geology,92, 153176.
Santo,A.P.&Peccerillo, A. 2008. Oxygen isotopic variations in the
clinopyroxenes from the Filicudi volcanic rocks (Aeolian Islands,
Italy): implications for open-system magma evolution. Open Miner-
alogy Journal,2, 112.
Santo, A. P., Jacobsen,S.B.&Baker, J. 2004. Evolution and genesis of
calc-alkaline magmas at Filicudi volcano, Aeolian Arc (Southern
Tyrrhenian Sea, Italy). Lithos,72, 73 96.
Schiavi, F., Kobayashi, K., Nakamura, E., Tiepolo,M.&Vannucci,
R. 2012. Trace element and Pb-B-Li isotope systematics of olivine-
hosted melt inclusions: insught into metasomatism beneath Stromboli
(southern Italy). Contributions to Mineralogy and Petrology,163,
1011 1031.
Sun, S.-S. & Mcdonough, W. F. 1989. Chemical and isotopic systema-
tics of oceanic basalts: implications for mantle composition and pro-
cesses. In:Saunders,A.D.&Norry, M. J. (eds) Magmatism in the
Ocean Basins. Geological Society, London, Special Publications, 42,
313 345.
Tommasini, S., Heumann,A.,Avanzinelli,R.&Francalanci,L.
2007. The fate of high-angle dipping slabs in the subduction
factory: an integrated trace element and radiogenic isotope (U, Th,
Sr, Nd, Pb) study of Stromboli Volcano, Aeolian Arc, Italy.
Journal of Petrology,48, 24072430.
Tonarini, S., Leeman, W. P., Civetta, L., D’antonio,M.,Ferrara,G.
&Necco, A. 2004. B/Nb and d
B systematics in the Phlegrean
Fields District, Italy. Journal of Volcanology and Geothermal
Research,133, 123 139.
Trua, T., Serri,G.,Marani, M. P., Rossi, P. L., Gamberi,F.&
Renzulli, A. 2004. Mantle domains beneath the southern Tyrrhe-
nian: constraints from recent seafloor sampling and dynamic impli-
cations. Periodico di Mineralogia,73, 53 73.
Trua, T., Marani,M.P.&Gamberi, F. 2011. Magmatic evidence for
African mantle propagation into the southern Tyrrhenian backarc
region. In:Beccaluva, L., Bianchini,G.&Wilson, M. (eds) Vol-
canism and Evolution of the African Lithosphere. Geological Society
of America, Boulder, Special Paper 478, 307331.
Ulmer, P. 2001. Partial melting in the mantle wedge – The role of H
the genesis of mantle-derived ‘arc-related’ magmas. Physics of Earth
and Planetary Interior,127, 215232.
Ventura, G. 2013. Kinematics of the Aeolian volcanism (Southern Tyr-
rhenian Sea) from geophysical and geological data. In:Lucchi, F.,
Peccerillo,A.,Keller, J., Tranne,C.A.&Rossi, P. L. (eds)
The Aeolian Islands Volcanoes. Geological Society, London,
Memoirs, 37, 312.
Viccaro,M.&Cristofolini, R. 2008. Nature of mantle heterogeneity
and its role in the short-term geochemical and volcanological evol-
ution of Mt. Etna (Italy). Lithos,105, 272 288.
Wilson,M.&Downes, H. 1991. Tertiary-Quaternary extension-related
alkaline magmatism in Western and Central Europe. Journal of Pet-
rology,32, 811 849.
Zanon,V.,Frezzotti,M.L.&Peccerillo, A. 2003. Magmatic feeding
system and crustal magma accumulation beneath Vulcano Island
(Italy): evidence from CO
fluid inclusions in quartz xenoliths.
Journal of Geophysical Research,108, 22982301.
Zindler,A.&Hart, S. 1986. Chemical geodynamcs. Annual Review of
Earth and Planetary Sciences,14, 493571.
... Several geochemical studies (e.g., Francalanci et al. 2007;Peccerillo et al. 2013;Zamboni et al. 2017) suggested that the along-arc geochemical variations of the mafic rocks reflect modification of an OIB to MORB mantle wedge by subducting components. For example, the increase of 87 Sr/ 86 Sr (0.7034-0.7075) and the negatively correlated decrease of 143 Nd/ 144 Nd (0.5129-0.5124) of mafic rocks from west to east along the Aeolian Arc in less than 100 km, are attributed to increasing mantle metasomatism by subduction components (fluids and melts). ...
... Faccenna et al. 2011), and at Vulcano and Lipari (central segment), fostered by a grabenlike structure along the Tindari-Letojanni fault system (Iacobucci et al. 1977; Barberi et al. 1994). Different structural, geochemical and volcanological features characterise the three sectors of the arc (e.g., Peccerillo et al. 2013). ...
... As regards the origin of parent magmas, current hypotheses on the genesis of the Aeolian primitive parents include: (i) MORB-plus OIB-type pre-metasomatic mantle wedge, where variable amounts and/or variable nature of fluids produced geochemical-isotope variability along the arc (Ellam et al. 1988;Peccerillo et al. 2013;Peccerillo 2017 and references therein) and (ii) homogeneous MORB-type pre-metasomatic mantle source subject to two metasomatizing events by fluids plus variable amounts of sediments (Francalanci et al. 1993Tommasini et al. 2007). ...
Full-text available
Vulcano is part of the Aeolian volcanic arc in the southern Tyrrhenian Sea. Its products were emplaced through multiple episodes of edifice building and collapse since about 120 ka B.P. to present. A major discontinuity in the activity occurred after about 28 ka, while the focus of volcanism moved from SE to NW. The older products are basalts to shoshonites, and have lower K2O than the younger ones, shoshonites to rhyolites. Between these two groups, Lentia latites-rhyolites, Spiaggia Lunga basalts, and Quadrara shoshonite-trachytes, erupted along the western side of Vulcano Island. The Spiaggia Lunga basalts (i) are the most primitive magmas erupted at Vulcano after 28 ka (ii) mark the change between older and younger phases, and (iii) overlap geochemically with a monzogabbroic intrusion of similar age. This work focuses on the Spiaggia Lunga products, discussed within a large dataset of geochemical and radiogenic isotope analyses on the entire Vulcano sequence. Older products have more primitive geochemical and isotope characteristics, and lower incompatible element contents, than younger ones. The Spiaggia Lunga basalts exhibit intermediate geochemical characteristics between the older and the younger groups, and can likely be regarded as a third magmatic phase, which represents a distinct mantle reservoir active during the magmatic history of Vulcano. Significant variations of Sr, Nd, and Pb isotope ratios, and isotopic disequilibrium between phenocrysts and groundmass, are present among the Vulcano products. This variability suggests crustal assimilation in shallow-level magma chambers, which also accounts for the formation of evolved products by combined assimilation and fractional crystallization, particularly in the younger series. Considering only the mafic products, incompatible element patterns with high LILE/HFSE and enriched signatures of Sr, Nd, and Pb isotope ratios, indicate enriched mantle sources. Besides, chemical and isotope variability among older, younger, and Spiaggia Lunga mafic rocks, suggests an origin from geochemically diverse primary melts, derived from distinct mantle reservoirs. Their parent magmas, based on geochemical and isotope patterns, were from both MORB- and OIB-type mantle sources, subject to variable degrees of metasomatism by subducted sediments.
... Indeed, δ 18 O of sediments vary from 8 to 30 (e.g., Bindeman, 2008) and strongly negative δ 37 Cl are usually attributed to the influence of sediments (e.g., Barnes and Sharp, 2017). Sediment influence beneath St. Vincent, Aoba, Vulcano, Iwate and Sukumoyama has also been proposed by other studies based on traces elements and/or stable isotopes (e.g., Bouvier et al., 2008;Manzini et al., 2017a;Métrich and Deloule, 2014;Nichols et al., 2012;Peccerillo et al., 2013;Rose-Koga et al., 2014). ...
Full-text available
Melt inclusions are often used to infer melting processes or to determine source magmas that are usually overprinted in bulk rocks due to late stage mixing or near surface contamination. Here we present the first investigation of oxygen (O) isotope equilibrium between melt inclusions and their host olivines from arc samples. Olivines in all but one sample record either magma mixing or fractional crystallization. All six melt inclusions from Vulcano, 83% of seven from Sukumoyama, 44% of 21 from St Vincent, 37% of four from Iwate, and 21% of 13 from Aoba are not in isotopic equilibrium with their olivine host, despite the other major elements being in apparent equilibrium. A detailed study of some of the olivines shows that only a small volume around the melt inclusions is in equilibrium with its host. This strongly suggests that in these olivines melt inclusions are trapped in partly recrystallized olivines, highlighting the importance of magma mixing and crystal recycling in the magmatic plumbing system of these volcanoes. Oxygen isotope fractionation between melt inclusions and their host olivines, as well as phosphorus-δ18O systematics, could be used to better understand the formation of melt inclusions and crystal history. It could also provide valuable information to help characterize the magmatic plumbing system that the inclusions and their olivine hosts formed in (e.g., crystal rich-mush versus crystal poor melt lenses).
... The quiescent Alicudi volcano is sited at the westernmost margin of the Aeolian archipelago ( Fig. 1) and, its subaerial portion is made up predominantly of lava flows and domes and minor pyroclastic rocks (Lucchi et al. 2013a). The Alicudi main volcanic products include calc-alkaline basalts and basaltic andesites (Villari 1980;Peccerillo et al. 2013), erupted during early phases of activity (c. 106 ka to 80 ka; Lucchi et al. 2013a), whereas andesites became dominant during latest stages of development of Alicudi (c. ...
Full-text available
The use of mineral interfaces, in sand-sized rock fragments, to infer the influence exerted by mechanical durability on the generation of siliciclastic sediments, has been determined for plutoniclastic sand. Conversely, for volcaniclastic sand, it has received much less attention, and, to our knowledge, this is the first attempt to make use of the volcaniclastic interfacial modal mineralogy of epiclastic sandy fragments, to infer mechanical durability control at a modern beach environment. Volcaniclastic sand was collected along five beaches developed on five islands, of the southern Tyrrhenian Sea (Alicudi, Filicudi, Salina, Panarea and Stromboli) from the Aeolian Archipelago, and one sample was collected near the Stromboli Island volcanic crater. Each sample was sieved and thin sectioned for petrographic analysis. The modal mineralogy of the very coarse, coarse and medium sand fractions was determined by point-counting of the interfacial boundaries discriminating 36 types of interfaces categories, both no-isomineralic and/or no iso-structural (e.g., phenocrystal/glassy groundmass or phenocrystal/microlitic groundmass boundaries) and iso-mineralic interfaces, inside volcanic lithic grains with lathwork and porphyric textures. A total of 47,386 interfacial boundaries have been counted and, the most representative series of interfaces, from the highest to the lowest preservation, can be grouped as: a) ultrastable interfaces, categorized as Pl (Plagioclase)/Glgr (Glassy groundmass) > > Px (Pyroxene)/Glgr > > Ol (Olivine)/Glgr > > Op (Opaque)/Glgr > > Hbl (Hornblende)/Glgr> > Bt (Biotite)/Glgr > > Idd (Iddingsite)/Glgr > > Rt (Rutile) / Glgr; b) stable interfaces, categorized as Pl/Migr (Microlitic groundmass) > > Op/Migr > > Px/Migr > > Ol/Migr; c) moderately stable interfaces, categorized as Op/Px > > Op/Hbl > > Px/P > > Ol/Pl> > Bt/Op; and d) unstable interfaces, categorized as Pl/Pl > > Px/Px > > Ol/Ol > > Op/Op > > Hbl/Hbl > > Bt/Bt. Grains, eroded from the volcanic bedrock, if affected solely by abrasion, developed a rounded and smoothed form, with prevailing no-isostructural interfaces such as Plagioclase/Glassy groundmass, Pyroxene/Glassy groundmass and Olivine/Glassy groundmass interfaces. Grains that during transport suffered fracturing and percussion have a sharp and angular form: these combined transport mechanisms produce mainly volcanic sandy grains with iso-structural interfaces, such as Pl/Pl, Px/Px, Hbl/Hbl, and, to a lesser extent, Bt/Op and Bt/Glgr interfaces.
... The Aeolian arc is related to the subduction of the Ionian-Adriatic lithosphere underneath the Calabrian arc. Mantle beneath the Aeolian arc volcanoes has been metasomatized by fluids from the Ionian oceanic crust and the sediments from the Ionian basin in the eastern part of the arc (Peccerillo et al., 2013). The selected OHMIs come from La Sommata scoria cone on Vulcano Island. ...
The effect that recycling crust and sediments have on the composition of the mantle wedge, in particular in terms of volatiles, is still debated. Chlorine, an important fluid mobile element that has stable isotopes with different concentrations in the terrestrial reservoirs, has the potential to be used to trace slab-derived fluids. Olivine-hosted melt inclusions (OHMIs) provide a first order constraint on the d37Cl of primary magmas, since they are unaffected by near surface processes. In this study, d37Cl were coupled with d11B and d18O analyses in samples from the Lesser Antilles, Vanuatu, Aeolian, NE Japan and Izu-Bonin arcs. This unique dataset is used to better understand the large d37Cl variation in melt inclusions from a single sample. OHMIs from the Vulcano (Aeolian arc) and Sukumoyama (Izu-Bonin arc) samples have similar d37Cl (−2.5 ± 0.5‰ and −2.6 ± 0.8‰, respectively). These are different from d37Cl in OHMIs from the other three localities (d37Cl of −0.7 ± 0.6‰ for Aoba (Vanuatu arc) and St. Vincent (Lesser Antilles arc), −1 ± 0.9‰ for Iwate (NE Japan)). Vulcano OHMIs also have statistically different d11B and d18O isotope compositions compared to those from the other locations: average d11B of −5.1 ± 2.9‰ for Vulcano OHMIs, compared to 2.5 ± 3.7‰, 5.2 ± 1.4‰, 7.0 ± 2.2‰, 3.8 ± 7.5‰ for Sukumoyama, Iwate, Aoba and St. Vincent OHMIs, respectively. All OHMIs have d18O between 4.0 and 7.4‰, except for those from Vulcano, which are significantly different, with d18O from 7.2 to 9.1‰. Combining these three stable isotope systems suggests that the large variation (>2‰) of d37Cl in OHMIs from a sample reflects inputs from different sources of Cl rather than heterogeneities in a single main source. Variability between arcs might reflect different major sources of Cl. Comparing OHMIs Cl isotope data from the Aeolian and Izu-Bonin arcs with existing bulk rock Cl isotope data suggest that OHMIs preserve the source signature of Cl input whereas this signal can be lost in whole rocks as a result of Cl isotope diffusive fractionation during Cl degassing. SIMS measurements of Cl isotopes in OHMIs could thus help refine models of Cl cycles in the mantle.
Full-text available
Subduction zones are places of voluminous material transport and element recycling between the Earth’s surface and its interior. Magmatism and hydrothermal activity at subduction zones are the surface expression of the complex physical and chemical interactions between the subducted crust and the mantle wedge. Large amounts of volatiles get dragged down within the hydrated oceanic crust and are released at increasing pressures and temperatures, starting their way back to the surface. The interaction of mantle rock with fluids and other slab-derived components causes partial melting of the mantle wedge, followed by magma ascent, evolution, and interaction with the overriding plate. The emplacement of magmas in the shallow crust is accompanied by the exsolution of volatiles that react with the surrounding rocks resulting in the formation of magmatic-hydrothermal ore deposits, which are significant metal resources for our society. Complex models of subduction dynamics have been established by geophysical and geochemical studies over the past decades, however, some questions remain open and a better understanding of the processes that control the formation and evolution of arc magmas and related mineralizations is still needed. The Aegean region, located in the eastern Mediterranean, was affected by subduction since the late Cretaceous and provides vast opportunities to study subduction zone processes. Northwards subduction and accretion of oceanic and continental fragments beneath Eurasia led to slab rollback, southward trench retreat, and extension of the overriding plate during the past ~35 million years. Subduction-related magmas and associated porphyry-epithermal ore deposits are spread over the entire region and thus, the Aegean is an ideal target to study the element transport via magmas and fluids from the mantle wedge to the shallow crust. This thesis shall investigate (i) the contribution of subducted sediments to arc magmatism in a migrating subduction system, (ii) the formation and evolution of subduction-related potassic magmas, (iii) the magmatic preconditions that promote porphyry-epithermal-style mineralization, and (iv) the hydrothermal processes that control the metal enrichment in the shallow crust. To approach these questions, we compiled a comprehensive geochemical data set of Aegean magmas to develop a new tectono-magmatic model for the Aegean (chapter 3). Furthermore, we analyzed whole rock, mineral, and ore samples from two focus areas, the shoshonitic Maronia pluton in northeast Greece (chapter 4), and the volcanic and hydrothermally active Milos Island (chapter 5), highlighting different depths and time windows of the Aegean subduction system. The compiled geochemical and geochronological data of Aegean magmas along two age-progressive profiles provides evidence for the migration of the magmatic arc due to the Aegean slab rollback. The strong variation of magma compositions can be linked to the subduction of heterogeneous sedimentary and continental material during the past 30 million years. The transfer of sediment components from the slab to the sub-arc magma source can be best explained by the mixing of mantle rock with bulk sediment and the ascent of this mélange material in buoyant diapirs causing focused arc magmatism. Temporal changes in the isotope and incompatible element composition of the magmas are correlated with the subduction of different sedimentary and continental material at variable subduction rates. To study the genesis of potassic magmas in detail, we use major element, trace element, and Sr-Nd-Pb isotope data of monzodioritic to granitic rocks from the shoshonitic Maronia pluton. Our findings imply that shoshonitic magmas can be produced in arc settings by low-degree partial melting of a mantle source, that has been enriched by slab-derived crustal material. In Maronia hydrous melting of the subduction-modified mantle was followed by magma ascent, fractional crystallization, and magma emplacement at a depth of 5 to 6 km. Microanalytical data of apatite implies the exsolution of Cl- and metal-rich, but S-poor fluids from late-stage granitic magma leading to porphyry Cu-Mo ± Re ± Au mineralization and associated formation of sulfide-bearing miaroles. The Pb-Zn-Ag vein mineralization on Milos Island records the conditions and processes that control the transport and precipitation of metals in the shallow crust of an arc volcano. We use S-Sr-Pb isotopes of sulfides and sulfate to identify the fluid and metal sources of the system. The mineralization formed by circulation and heating of seawater, leaching of metals from the volcanic and metamorphic host rocks, and subsequent precipitation of sulfides at decreasing temperatures during fluid ascent along major fault zones. Based on in-situ trace element and S isotope data of sulfides, we can show that boiling and fluid-seawater mixing in the subseafloor control the vertical distribution of metals and metalloids in shallow-marine hydrothermal systems. Altogether, this thesis provides important new insights into the processes that control the element transfer in subduction zones from the mantle wedge to the shallow crust. In contrast to previous studies, we can show that the subduction of variable sedimentary and continental material accounts for the large range of Cenozoic magma compositions including K-rich magmas in the Aegean. The shallow emplacement of oxidized, volatile-rich magmas and the interplay of mafic and felsic magmas facilitates the formation of magmatic-hydrothermal mineralizations in the thinned arc crust. Additionally, the physicochemical conditions during boiling and fluid mixing control the transport and precipitation of metal(loid)s in shallow-crustal hydrothermal systems.
Full-text available
Compiled data show the age progression of magmatic centers along two approximately linear profiles from NE Greece and NW Turkey to the South Aegean Volcanic Arc (SAVA). The age progression reveals the southwestward migration of arc magmatic activity from Oligocene to present, perpendicular to the Hellenic Trench. This is in accordance with the migration of the Aegean subduction zone due to the collision of oceanic and continental blocks, trench retreat, mantle flow, and coeval extension. We suggest that the subduction of large volumes of sediments and their contribution to the sub-arc magma source controlled the composition of calc-alkaline to high-K calc-alkaline and shoshonitic arc magmas during the past 30 Ma. The magma geochemistry and the approximately linear age-progressive migration of magmatic activity suggest focused ascent of mixed material from the subducted slab into the mantle wedge, most likely in the form of mélange diapirs. Geochemical data along the profile reveals increasing Sr and decreasing Nd isotopes during Upper Miocene in agreement with the ongoing subduction of continental blocks, low subduction rates, and development of an accretionary wedge. The different K-rich arc magmas reflect the variable subduction of sediments, whereas crustal assimilation often plays a minor role. Magmas with variable 87Sr/86Sr, P/Nd, and Ba/La indicate a variable contribution of clastic, phosphate-, and barite-bearing sediments. Low-degree partial melting in sediment-dominated mélange diapirs causes the formation of shoshonitic magmas with high Sr and P2O5 contents and high La/Yb in the northern Aegean.
The Ancient GreeksAncient Greeks settled many of the coastal areas in southern ItalyItaly and the Italian IslandsItalian Islands. Well known archaeological sites of Magna GraeciaMagna Graecia include PaestumPaestum, near NaplesNaples, which includes three well-preserved temples, and SyracuseSyracuse in SicilySicily. MythologyMythology was an important part of the Ancient World and the difficulties that OdysseusOdysseus experienced on his return voyage from TroyTroy (western TurkeyTurkey) to his home island of IthacaIthaca (northwest GreeceGreece), as recounted by the Greek poet HomerHomer, Greek poet, contain descriptions of the perils of navigating the Mediterranean SeaMediterranean Sea. The historical (and mythological) record includes geological catastrophes such as earthquakesEarthquakes, volcanic eruptionsVolcanic eruption, tsunamisTsunami, and tidal whirlpoolsWhirlpool. The Stromboli VolcanoStromboli Volcano has been described as the world’s oldest lighthouse as the glow of the vent can be seen from many kilometres at night. The Mediterranean is comprised of multiple interlocking basins, each of which contains a sea identified by the ancient geographers. The Adriatic SeaAdriatic Sea, the Aegean SeaAegean Sea, the Ionian SeaIonian Sea, and the Tyrrhenian SeaTyrrhenian Sea each have different physical and chemical characteristics. Large parts of the central and eastern Mediterranean remain tectonically active. The Alpine OrogenyAlpine Orogeny is a long drawn out process of continental collision associated with the northward-migrating African PlateAfrican Plate and the Eurasian PlateEurasian Plate. Tectonism peaked in the Oligocene-Miocene with formation of multiple chains of fold mountainsFold Mountains. The collision is ongoing and includes subductionSubduction of oceanic crustOceanic crust associated with the ancient Tethys OceanTethys Ocean. The complexity of the tectonic setting is illustrated by the recognition of microplates, as well as the curvilinear nature of the Hellenic TrenchHellenic Trench, the current location of the plate boundary. The compressional tectonism was displaced in the PliocenePliocene by localized regions of crustal extension. Crustal extension associated with development of fore-arc and back-arc basinsBack-arc basin has resulted in some regions being subjected to frequent and relatively shallow, earthquakesEarthquakes. Catastrophic events between 1169 and 1908 resulted in the destruction of the cities of CataniaCatania and MessinaMessina. The Italian IslandItalian Island volcanoes are related to the convergent plate boundaries. There are several potentially hazardous volcanoes in the Aeolian Islands, including StromboliStromboli Island and the Fossa coneFossa cone, associated with aVolcanic island arcvolcanic island arcIsland arc (Volcanic island arc). The StrombolianStrombolian, volcanism style of volcanismVolcanism is characterized by relatively small eruptions constrained to discrete cratersCrater. The Fossa coneFossa cone on the island of VulcanoVulcano, island (named after VulcanVulcan, Roman god of fire, the Roman god of fire) is characterized by short-lived, yet violent eruptions. The Etna VolcanoEtna Volcano in northeast SicilySicily is one of the largest stratovolcanoesStratovolcano on Earth and also one of the most active. Historical activity includes the 1669 eruption during which lava flowed into the city of CataniaCatania. EtnaEtna Volcano is a major tourist attraction and the volcanic coneVolcanic cone is protected in a national park. Recent eruptions of EtnaEtna Volcano are generally restricted to the upper parts of the cone, but can be sufficiently hazardous as to restrict tourist visits. The small island of PantelleriaPantelleria, island is part of an active volcanic system associated with a transform faultTransform fault on the plate boundary between SicilySicily and North Africa.
The Present-day (<1.2 kyr) activity of Stromboli (Aeolian Islands, Southern Italy) is fed by a vertically-extended mush column with an open-conduit configuration. The eruptive products are the result of periodic supply of mafic magma (low porphyritic or Lp-magma) from depth into a homogeneous shallow reservoir (highly porphyritic or Hp-magma). Clinopyroxene phenocrysts from the 2003–2017 activity exhibit marked diopside-augite heterogeneities caused by continuous Lp-Hp magma mixing and antecryst recycling. Diopsidic bands record Lp-recharge injected into the shallow Hp-reservoir, whereas resorbed diopsidic cores testify to the continuous disruption and cannibalism of relic antecrysts from the mush. The transition between diopside (∼1175 °C) and augite (∼1130 °C) takes place at comparable P (∼190 MPa) and H2O (0.5–2.4 wt%) conditions. Short timescales (∼1 year) for diopsidic bands from the 2003 paroxysm document restricted temporal intervals between mafic injection, magma mixing and homogenization in the Hp-reservoir. Longer timescales (∼4–182 years) for diopsidic cores indicate protracted antecryst remobilization times. By comparing clinopyroxenes from the Present-day and Post-Pizzo eruptions, we argue a distinct phase in the life of Stromboli volcano is evident from the 2003 paroxysm onwards. More efficient mechanisms of mush disruption and cannibalism involve diopsidic antecrysts remobilized and transported by Lp-magmas permeating the mush, in concert with gravitational instability of the solidification front and melt migration within the shallow Hp-reservoir. Magmatic injections feeding the persistent Present-day activity are more intensively mixed and homogenized prior to eruption, reflecting small recharge volumes and/or a more mafic system in which the mafic inputs are less pronounced.
Full-text available
We constrained the origin and genetic environment of modern iron ooids (sand-sized grains with a core and external cortex of concentric laminae) providing new tools for the interpretation of their fossil counterparts as well as the analogous particles discovered on Mars. Here, we report an exceptional, unique finding of a still active deposit of submillimetric iron ooids, under formation at the seabed at a depth of 80 m over an area characterized by intense hydrothermal activity off Panarea, a volcanic island north of Sicily (Italy). An integrated analysis, carried out by X-ray Powder Diffraction, Environmental scanning electron Microscopy, X-ray Fluorescence and Raman spectroscopy reveals that Panarea ooids are deposited at the seafloor as concentric laminae of primary goethite around existing nuclei. The process is rapid, and driven by hydrothermal fluids as iron source. A sub-spherical, laminated structure resulted from constant agitation and by degassing of CO2-dominated fluids through seafloor sediments. Our investigations point the hydrothermal processes as responsible for the generation of the Panarea ooids, which are neither diagenetic nor reworked. The presence of ooids at the seawater-sediments interface, in fact, highlights how their development and growth is still ongoing. the proposed results show a new process responsible for ooids formation and gain a new insight into the genesis of iron ooids deposits that are distributed at global scale in both modern and past sediments.
Full-text available
SUMMARY: Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (≤1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (≤2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by
Full-text available
Stromboli is famous for its persistent volcanic activity consisting of periodic discrete explosions alternating with lava effusion and more violent explosions. This paper presents a detailed reconstruction of the geological history of Stromboli and description of the characteristics and distribution of the volcanic units and structural features. Six main growth stages (Eruptive Epochs 1–6), in addition to the c. 200 ka activity of Strombolicchio, are recognized between c. 85 ka and the present day, displaying a magma composition ranging from calc-alkaline to potassic series which usually varies with changing Eruptive Epochs. The Epochs are subdivided into sequences of eruptions and characterized by dominant central-vent summit activity with episodic phases of flank activity along fissures and eccentric vents. The activity was repeatedly interrupted by erosional and destructive phases driven by recurrent vertical caldera-type (cc1–5) and sector (and flank) collapses (sc1–7) and generally associated with significant quiescences. The different serial character of the Stromboli rocks is associated with largely variable trace element contents and isotope ratios. These petrochemical characteristics together with our new stratigraphy indicate that magmas, generated in a heterogeneous mantle wedge, underwent complex differentiation processes during their ascent. Magmas are characterized by polybaric evolution residing in small magma reservoirs that are alternatively tapped by the different collapses. DVD The 10 000 scale geological map of Stromboli is included on the DVD in the printed book and can also be accessed online at . Also included is a full geochemical dataset for Stromboli.
In this contribution, the analytical capabilities of the Laser Ablation - Inductively Coupled Plasma - Mass Spectrometer (LA-ICP-MS) instrumentation installed at the Earth Sciences Department of Perugia University are evaluated. The instrumental set up and the analytical protocols for single-phase spatially-resolved and bulk trace-element analyses are presented. Spatially-resolved analysis allow 'in situ' trace element determinations with lateral resolutions ranging from less than 20 mu m to more than 80 mu m. Precision (expressed as relative standard deviation) is better than 10% with the only exception of Cs (14% with a 20 mu m laser beam diameter) whereas accuracy (expressed as relative deviation from the reference value) is better than 11%. Precision and accuracy increase as increasing the laser beam diameter. The extreme versatility of the instrument permits to analyze with excellent results compositions of crystals, melt inclusions, ceramics, archaeological, and environmental samples. Bulk configurations are utilized to perform whole-rock trace-element determination on samples prepared as fusion beads. Both flux-free and lithium tetraborate fusion sample preparation for whole rock trace element determination are investigated. Results show that the lithium tetraborate fusion produces beads with higher degrees of homogeneity compared to the flux-free method, resulting in more precise and accurate trace-element determinations. In detail, for the lithium tetraborate fusion precision is better than 10% for elements with concentrations above 2 mu g/g with the only exception of Ph (similar to 15%). For elements with concentrations below 2 mu g/g the precision decreases to about 15%. Accuracy values are always better than 10% with the only exception of Pb.
The crystal chemistry of clinopyroxenes from calc-alkaline volcanic rocks from the island of Alicudi (Aeolian Arc) was studied by single-crystal X-ray diffraction and microprobe techniques, in order to explore the relationships between clinopyroxene structural and chemical parameters and the physicochemical conditions of their crystallization. Crystal chemical data indicate considerable differences between clinopyroxenes from early eruptive stages and those from the latest volcanic activity. Early-stage clinopyroxenes are characterized by smaller cell volumes and a more closely packed structure than late clinopyroxenes, suggesting a higher pressure of crystallization for the early clinopyroxenes. The crystal chemical pattern of clinopyroxene follows an overall trend of rock composition, which is basaltic and andesitic-basaltic for the earliest products and becomes slightly more acidic at the end of volcanic activity. This geochemical and petrologic evolution is also found in other Aeolian islands and may be explained by assuming the increasing role of crystal fractionation with respect to mixing with primary mafic melts. The variations in crystal chemical parameters of clinopyroxenes at Alicudi, which indicate decreasing pressure of crystallization with time, lend support to the hypothesis of polybaric evolution of the Alicudi magmas.