1,721,141 research outputs found
Arienzo I., MORETTI R., Civetta L., Orsi G., Papale P. (2008) The feeding system of Agnano-Monte Spina eruption (Campi Flegrei, Italy): dragging the past into present activity and future scenarios
No full textThe Agnano Monte Spina (Campi Flegrei, Italy ( 4100 years BP) eruption is a reference scenario for a next large scale eruption at Campi Flegrei caldera, and is here selected to investigate the physico-chemical conditions of the pre-eruptive magmatic system as well as to gain insights into the source processes responsible of the huge hydrothermal-magmatic activity observed at surface nowadays. Isotope data on whole rocks and glasses and melt inclusions studies suggest that two chemically and isotopically distinct magmas, with different volatile signature mixed before the eruption. Our new data reveal that one of the magmas involved in the mixing process is similar to the less differentiated shoshonitic magma erupted at around 10 ka BP, whereas the second represents a residual of the magma discharged during the Neapolitan Yellow Tuff caldera forming eruption. Hence, the mixing process is driven by an abundant gas phase which sustains the ascent of magma blobs of deep provenance. The H2O and CO2 contents in melt inclusions give entrapment pressures between 60 and 150 MPa, corresponding to depths between 2.5 and 6 km. Degassing trends show the presence of two extreme patterns, one likely to represent the volatile signature of magma ascending from depth > 7 km; the other one related to a gas-dominated magma residing at shallow depth and developed upon flushing by deep CO2-rich gas. We suggest that volatile- rich blobs of deep shoshonitic magma periodically ascended and mixed with trachy-phonolitic magma at shallower depths. Our model is consistent with the bulk of geophysical and petrological observations at Campi Flegrei, and allows us to outline the role of magma mixing as a primary feature at Campi Flegrei caldera, as supported by the results of previous investigation of other eruptions in the area A major outcome of this study is the conceptual frame it deserves for recent unrest crises at Campi Flegrei, including the 1982-84 bradyseism. Uplift phases associated to bradyseismic crises are related to major episodes of closed-system ascent of magma blobs from depth > 7 km, followed by single-step volatile release upon their emplacement at shallow levels (3-4 km). This leads both the shallow magmatic and geothermal systems to store and progressively release important amounts of gas, hence energy. In this view, eruptive episodes are strongly conditioned by the critical achievement of an upper limit of gas storage, and by the crustal stress state and the fracturing state of the overlying cap of rocks
Sr-He-O isotopes in mafic phenocrysts from products of the Neapolitan volcanoes (southern Italy): constraints on the geochemical features of the mantle sources
No full textAn investigation through Sr-He-O isotopes and major oxides was carried out on Mg-rich olivine and clinopyroxene
phenocrysts from a selection of volcanic rocks of the Neapolitan Volcanoes (southern Italy), which include Somma-
Vesuvius, Phlegraean Fields, and the islands of Ischia and Procida. The data produced in the present work extend the
Sr-He-O dataset available for the Neapolitan volcanic districts (e.g., Graham et al., 1993; Martelli et al., 2004; Di Renzo
et al., 2011; D’Antonio et al., 2013; Iovine et al., 2017), improving the knowledge especially on helium isotopic
compositions of the Mt. Somma rocks, never analysed before. 3He/4He ratios (2.60-5.12 R/RA) of the investigated Mgrich
phenocrysts are markedly lower than those measured at most volcanic arcs worldwide, and are among the lowest
measured in subduction zones. This range of 3He/4He is coupled with quite large ranges of 87Sr/86Sr (0.704882 –
0.708480) and δ18O (4.85 – 6.70‰) measured in the same mafic minerals. The 3He/4He values, and the lowest measured
Sr- and O-isotope ratios, do not suggest significant crustal or fluid contamination occurred during magmatic evolution,
and they should reflect the composition of the metasomatized mantle beneath the Neapolitan region. Moreover, these
values display a clear geographic trend, with radiogenic 4He-87Sr, and 18O generally increasing in on-lands districts. The
results of these investigations are expected to allow us to better understand the original characteristics of the mantle
source(s), and to define those of other components, likely originated in the continental crust, that were involved in the
genesis of the primitive magmas feeding the Neapolitan volcanoes. D’Antonio, M., Tonarini, S., Arienzo, I., Civetta, L., Dallai, L., Moretti, R., Trecalli, A. (2013): Mantle and crustal processes in the
magmatism of the Campania region: inferences from mineralogy, geochemistry, and Sr–Nd–O isotopes of young hybrid
volcanics of the Ischia island (South Italy). Contrib. Mineral. Petrol., 165, 1173-1194.
Di Renzo, V., Arienzo, I., Civetta, L., D'Antonio, M., Tonarini, S., Di Vito, M.A., Orsi, G. (2011): The magmatic feeding system of
the Campi Flegrei caldera: architecture and temporal evolution. Chem. Geol., 281, 227-241.
Graham, D.W., Allard, P., Kilburn, C.R.J., Spera, F.J., Lupton, J.E. (1993): Helium isotopes in some historical lavas from Mount
Vesuvius. J. Volcanol. Geotherm. Res., 58, 359-366.
Iovine, R.S., Mazzeo, F.C., Arienzo, I., D’Antonio, M., Wörner, G., Civetta, L., Orsi, G. (2017): Source and magmatic evolution
inferred from geochemical and Sr-O-isotope data on hybrid lavas of Arso, the last eruption at Ischia island (Italy; 1302AD). J.
Volcanol. Geotherm. Res., 331, 1-15.
Martelli, M., Nuccio, P.M., Stuart, F.M., Burgess, R., Ellam, R.M., Italiano, F. (2004): Helium-strontium isotope constraints on
mantle evolution beneath the Roman Comagmatic Province, Italy. Earth Planet. Sci. Letters, 224, 295-308
Lithium isotope composition as tracer of crust/mantle interaction at subduction zones: a pilot study to understand the magma genesis of the Plio-Quaternary volcanic areas of Central Italy
No full textIn the framework of the FISR 2015-2016 “Centro di studio e monitoraggio dei rischi naturali dell’Italia
Centrale” project, we carried out a pilot study on the application of the lithium-isotope systematics to selected
igneous rocks, in order to shed new light on the nature of subduction components involved in the genesis of
magmas feeding the Roman Magmatic Province (Central Italy).
On the Earth, the two lithium isotopes, 6Li and 7Li, are susceptible to separation due to their relatively
large difference in mass (i.e., fractionation) as natural processes occur. These include mineral formation
(chemical precipitation), ion exchange (Li substitutes for Mg and Fe in octahedral sites in clay minerals,
with 6Li preferentially substituted over 7Li), and rock alteration. Among the available techniques, Thermal
Ionization Mass Spectrometry (TIMS) is inherently the most precise method for determination of the Li isotope
composition. In the last two decades, considerable progress has been made to minimize mass fractionation
during TIMS analysis. To date, no Li investigations have been performed on groundwater and volcanic
products from the Italian volcanoes to study water-rock interaction and/or magmatic processes, except for
Stromboli volcanics. This study acts as a driving factor towards the utilization of the Li-isotope systematics for
future studies, and can be considered as a first step towards the realization of a geochemical database including
Li isotopes, integrated with the available Sr, Nd, Pb, Hf, B and O isotopes on Italian Plio-Quaternary volcanic
rocks.
The final aim of this pilot study is to test the application of the Li-isotope systematics to shed new light
on the geochemical features of the subduction components involved in the genesis of magmas that fed the
activity of Colli Albani Volcanic District (Central Italy; e.g., Gaeta et al., 2016 and references therein). This
goal will be achieved by analyzing the Li isotope ratios of well-characterized (chemically and isotopically)
samples representative of eruptive products of the district, emplaced in the time window from 600ka to 40ka.
The activities carried out include: 1. Set up of the procedures to be adopted in clean chemistry laboratory
for extracting Li from natural samples; 2. chromatographic separation of Li in the NIST L-SVEC and USGS
BHVO-2 (batch #0759) standard samples, after acid dissolution; 3. Set up of the procedures for measuring Li
isotope ratios by TIMS.
Acknowledgements: This work benefited from financial support from FISR 2015-2016 “Centro di studio e
monitoraggio dei rischi naturali dell’Italia Centrale” project.
Gaeta, M., Freda, C., Marra, F., Arienzo, I., Gozzi, F., Jicha, B. & Di Rocco, T. (2016): Paleozoic metasomatism at
the origin of Mediterranean ultrapotassic magmas: Constraints from time-dependent geochemistry of Colli Albani
volcanic products (Central Italy). Lithos 244, 151-164
Raw materials for ancient ceramic productions from Campania region: provenance studies by means of Sr-Nd isotopes
No full textWhen archaeometric studies on archaeological ceramics are performed, one of the most important questions
asked by archaeologists is the provenance of pottery. This is usually performed by comparing mineropetrographic
and chemical composition of ceramics with that of local raw materials (clays, temper), production
indicators and appropriate reference groups. Nevertheless, the commonly-used analytical techniques (e.g. OM,
SEM-EDS, XRF, ICP-MS) may not always be helpful for the determination of provenance. Indeed, processing
of raw materials, such as tempering or levigation, can significantly modify their original chemical composition,
sometimes leading to an ineffective identification of raw material resources. For this reason, a pioneering
analytical approach has been recently applied by measuring the Sr and Nd isotopic signature.
Isotope analysis has largely used in archaeological sciences to date objects and identify their provenance,
making it also a useful tool for the determination of provenance of ceramic vessels (De Bonis et al., 2018 and
references therein). For this study, 87Sr/86Sr and 143Nd/144Nd isotope ratios were measured on archaeological
pottery from Campania and raw materials (clays and volcanic temper) exploited in antiquity for producing
ceramics. The analyses were focused on samples from both the Bay of Naples and Southern Campania. The
isotope signatures allowed us to better discriminate among different productions and find a strong relationship
between the archaeological pottery and the geological sources of raw materials.
In order to validate the method, Sr-Nd isotope ratios were also measured for the first time on experimental
ceramic materials that replicate archaeological pottery (De Bonis et al., 2018). It was interesting to note that
synthetic mixtures used for the ceramic replicas plot exactly on the theoretical mixing curve between the
clay and volcanic temper end-members. This suggests that the artificial manipulation of raw materials (firing,
levigation, tempering) induces no significant variations to the Sr-Nd isotope fingerprint, which strictly depends
on the geochemical affinity of the raw materials. Thus, isotopic analysis can be considered as an effective
and robust method that could complement the common multi-analytical approach in order to more precisely
constrain potential geological sources for ceramic materials and pottery provenance.
De Bonis, A., Arienzo I., D’Antonio, M., Franciosi, L., Germinario, C., Grifa, C., Guarino, V., Langella, A. & Morra, V.
(2018): Sr-Nd isotopic fingerprint as a tool for ceramic provenance: application on raw materials, ceramic replicas and
ancient pottery. J. Archaeol. Sci., 94, 51-59
Magmatic processes inferred from geochemical and Sr-Nd-isotopic data on the < 5 ka Zaro lava complex, Ischia Island (southern Italy)
No full textThe Zaro lava complex, located on the western sector of the Ischia volcanic island (Gulf of Naples, southern Italy),
is the product of one of the few effusive eruptions occurred in the last period of activity (< 5 ka). The complex is made
up of a white trachytic main lava flow (Zaro lava s.s.), hosting rounded-shaped enclaves of both mafic (shoshonite) and
felsic (trachyte) composition. Major and trace elements and isotopic (87Sr/86Sr and 143Nd/144Nd) data have been acquired
on whole rocks and separated minerals. Mafic enclaves (Mg# = 60-62, CaO = 7.71-8.31 wt%, Cr =117-143 ppm, Ni =
52-61 ppm, Zr =150-164 ppm, Sr = 503-526 ppm, LREE enriched compared to HREE) have low 87Sr/86Sr (0.70495-
0.70501) and high 143Nd/144Nd (0.51268-0.51269). Trachytic lavas and felsic enclaves (SiO2 = 60.61-61.71 wt%, K2O =
6.51-7.43 wt%, Na2O = 5.00-6.83 wt%, Rb = 243-428 ppm, Sr = 90-158 ppm, Zr = 385-773 ppm) exhibit higher
87Sr/86Sr (0.70608-0.70615) and lower 143Nd/144Nd (0.51255-0.51256). The strong isotopic difference between mafic
enclaves and trachytes rules out a simple crystallization process for the variable facies of the Zaro lava complex.
Moreover, in mafic enclaves petrochemical and possibly isotopic disequilibria between phenocrysts and their host rocks
suggest occurrence of mingling processes or crystals entrapment from a distinct magmatic phase: indeed, many
clinopyroxene and feldspar crystals are in chemical equilibrium with more evolved compositions (trachytic to
trachyphonolitic). Trachytic lavas and felsic enclaves are chemically similar and do not display isotopic disequilibria
between phenocrysts and host rocks.
The last 5 ka of volcanic activity at Ischia were characterized by emplacement of products resulting from interaction
between chemically and isotopically distinct batches of magma (Cava Nocelle, Vateliero and Molara; D’Antonio et al.,
2013). Although these products show features comparable to those of the Zaro mafic enclaves, the last have
significantly lower Sr and higher Nd isotopic ratios. Therefore, enrichment processes, such as assimilation of
continental crust or mantle contamination in different conditions, should be invoked to justify the difference in isotopic
features. Additionally, although the two evolved facies of the Zaro lavas have comparable chemical compositions and
“uniform” isotopic signature, field analysis shows evidence of mingling between similar magmas with different
viscosities. This process could have played a significant role in triggering the eruption.
D’Antonio, M., Tonarini, S., Arienzo, I., Civetta, L., Dallai, L., Moretti, R., Orsi, G., Andria, M., Trecalli, A. (2013): Mantle and
crustal processes in the magmatism of the Campania region: inferences from mineralogy, geochemistry, and Sr–Nd–O isotopes
of young hybrid volcanics of the Ischia island (South Italy). Contrib. Mineral. Petrol., 165,1173-1194
The magmatic system of Ischia island: another piece in the puzzle of the fluid-saturated, CO2-sustained, Neapolitan volcanism (Southern Italy)
No full textMelt inclusions in phenocrysts from some shoshonite to latite eruptive products of Ischia Island (Southern Italy)
provide a window on the deep magmatic feeding system. Together with similar products from the other Neapolitan
volcanoes (Procida, Campi Flegrei and Somma-Vesuvius), they probe the deep physico-chemical conditions of
magmas generated in a mantle contaminated by slab derived fluids/melts largely dominated by CO2.
The analyzed melt inclusions bear clear evidence for CO2 dominated gas fluxing and consequent dehydration of
magma portions stagnating at major crustal discontinuities. In general, magma differentiation at Ischia takes place
under very oxidized conditions determined by an unusual, nearly equimolar, proportion of divalent and trivalent
iron in the melt.
Budgets of magma degassing show that at Ischia there is much less magma than that needed to directly supply the
amount of magmatic fluids released at surface, thus constraining the role of CO2 rich deep fluids in originating the
volcanism and generating caldera resurgence.
The acquired data, together with those from the other Neapolitan volcanoes, show that, despite the compositional
and eruptive style differences within the poorly extended Neapolitan Volcanic area, the different kinds of volcanism
are linked by supercritical CO2 fluids produced by devolatilization of subducted terrigenous-carbonatic metasediment,
that infiltrate the mantle wedge, generate magmas and control their ascent up to eruption. In particular,
fluid upraise and accumulation at crustal levels beneath Neapolitan volcanoes occurs with different flow-rates that
depend on the major geological structures, particularly NW-SE normal and NE-SW transfer regional fault system
The deep plumbing system of the Ischia island: a physico-chemical window on the fluid-saturated and CO2-sustained volcanism of Campania volcanoes (Southern Italy)
No full textCampanian Ignimbrite cataclysmic eruption reveals the interplay between discharge of a foamy cap, caldera collapse, magma depressurization, and generation of extremely diluted pyroclastic currents
No full textThe late Pleistocene trachytic Campanian Ignimbrite (CI; 300 km3 DRE) covers the
Campanian Plain near Naples, and is found behind ridges more than 1,000 m high at 80
km from source, the Campi Flegrei caldera. Distal ignimbrite deposits reveal downhill
and/or downvalley flow directions prior to deposition, whereas in the absence of
significant topography, deposition came from a flow moving in a roughly radial direction.
These features point to very dilute currents, that together with the huge amount of
discharged magmatic material, suggest a magma reservoir highly enriched in volatiles,
rather than fluid entrainment from hydrothermal bodies or seawater.
Petrologic and geochemical modelling of erupted products and their chemical and textural
zoning, together with MI-based studies of gas-melt saturation, corroborate this view and
show that the CI huge volume differentiated and mixed at shallow depth (6-3 km). The
progress of crystallization yielded high-water contents (up to 6-7 wt%), thus producing an
overpressurized CO2-dominated gas cap (about 150 km3), uniformly distributed at the top
of the magma chamber. The onset of the eruption tapped this cap, with consequent
depressurization and fast volume decrease that facilitated or even drove the caldera
collapse, and allowed the water-rich magma to be discharged during the pyroclastic
current phase. The gas saturation-based estimates of the tapped foamy magma are
compatible with the extent of magma chamber roof collapse, strong expansion revealed
by textural data and transport and deposition mechanisms, reflecting depressurization
and magma inflation within the collapsed and laterally confined caldera
Three isotopically distinct components in the magmagenesis of the Phlegrean Volcanic District
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