Estimation of pre-eruptive magmatic water fugacity in the Phlegrean Fields, Naples, Italy

Fabbrizio, Alessandro; Scaillet, Bruno; Carroll, M.

doi:10.1127/0935-1221/2009/0021-1873

Cited by 11 publications

(8 citation statements)

References 28 publications

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“…Also, our pressure estimates for the reservoirs feeding the post-Pompeii eruptions are in good agreement with the results of both experimental petrology and MI studies 45 46 47 48 . The pressure value of the magmatic reservoir of the Pomici di Base eruption deduced from the Cl-buffering effect (100 ± 10 MPa) strongly contrasts with that obtained on feldspar geobarometers (300–400 MPa) 49 while it is coherent with the estimates resulting from water fugacity-based studies (below 165 MPa) 50 . Modelling Cl concentrations in the silicate melt at 300–400 MPa gives unrealistic values.…”

Section: Discussionsupporting

confidence: 62%

Chlorine as a geobarometer for alkaline magmas: Evidence from a systematic study of the eruptions of Mount Somma-Vesuvius

Balcone-Boissard

Boudon

Cioni

et al. 2016

Sci Rep

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Defining the magma storage conditions of a volcanic system is a major goal in modern volcanology due to its direct implications for the style of a possible eruption, and thus on the associated risk of any crisis and the necessary management and mitigation strategies. Below 200 MPa and at equivalent depths, the strongly non-ideal behaviour of the H-C-O-S-Cl-F system in the silicate melt causes unmixing of the fluid phase to form an H2O-rich vapour and a hydrosaline phase in equilibrium with the silicate melt, both responsible for buffering the chlorine (Cl) concentration. Following this equilibrium, the Cl concentration in melts may be used as a geobarometer for alkaline magmas. Systematic application of this method to the main explosive eruptions of Mount Somma-Vesuvius highlights two main magma ponding zones, at ~180–200 and ~100 MPa. At these pressures, the maximum pre-eruptive H2O contents for the different magma compositions can be estimated; the results obtained, largely in agreement with the current literature, therefore confirm the validity of the method. The Cl geobarometer may help scientists to define the variation of the magmatic reservoir location through time and thus provide strong constraints on pre-eruptive conditions, which are of utmost importance for volcanic crisis management.

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Section: Discussionsupporting

confidence: 62%

Chlorine as a geobarometer for alkaline magmas: Evidence from a systematic study of the eruptions of Mount Somma-Vesuvius

Balcone-Boissard

Boudon

Cioni

et al. 2016

Sci Rep

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“…Parameters used in simulations are independent of isotopic inversion of fumarolic data and are based on melt inclusion (MI) studies and experimental petrology (Roach, 2005;Fabbrizio et al, 2009). Adopted total H 2 O and CO 2 contents (Table 1) are from MI studies of the shallow magmatic system feeding recent trachytic eruptions at CFc (Arienzo et al, 2010).…”

Section: Magmatic Degassingmentioning

confidence: 99%

Multiple magma degassing sources at an explosive volcano

Moretti

Arienzo

Civetta

et al. 2013

Earth and Planetary Science Letters

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Persistent degassing of closed-conduit explosive volcanoes may be used to inspect and monitor magmatic processes. After interaction with shallow hydrothermal fluids, volcanic gases collected at surface can differ substantially from those exsolved from magma. We report here on an innovative approach to identify and separate the contribution of variable magmatic components from fumarolic gases, by processing the 30-year-long geochemical dataset from the Campi Flegrei caldera, Southern Italy. The geochemical record shows periodic variations, which are well correlated with geophysical signals. Such variations are interpreted as due to the time-varying interplay of two magma degassing sources, each differing in size, depth, composition, and cooling/crystallization histories. Similar multiple degassing sources are common at explosive volcanoes, with frequent ascent and intrusion of small magma batches. Our innovative method permits the identification of those magma batches, which contributes to the interpretation of unrest signals, forecasting and assessment of volcanic hazards.

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“…Only one experimental study has been performed starting from a phono-trachytic liquid, in order to determine the storage conditions of the Breccia Museo eruption in the Phlegrean Fields in Italy (Fabbrizio & Carroll, 2008;Fabbrizio et al, 2009). Yet, this study concerns alkaline magmas in a subduction context (not rifting as for CDP).…”

Section: Comparison With the Trachytic System Of The Phlegrean Fieldsmentioning

confidence: 99%

“…Yet, only a few of such studies have been dedicated to the determination of storage conditions of trachytic magmas (i.e. Phlegrean Fields; Fabbrizio & Carroll, 2008;Fabbrizio et al, 2009), leading to the conclusion that this class of magmas may hold a significant amount of dissolved water. Significant amounts of gases, combined to their silicarich nature, make trachytes prone to explosive behaviour, through processes that need to be fully understood in order to minimize the associated risks.…”

Section: Introductionmentioning

confidence: 99%

Trachyte Phase Relations and Implication for Magma Storage Conditions in the Chaine des Puys (French Massif Central)

Martel

Champallier

Prouteau

et al. 2013

Journal of Petrology

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Petrological data have been acquired on the natural trachytes from the Chaîne des Puys, French Massif Central, and on experimental products from phase equilibria in order to (i) constrain the storage conditions of the trachytic magmas that lead to explosive eruptions (dome destructions as block-and-ash flows or pumice-and-ash flows) and (ii) provide phase relationships and chemical compositions for differentiated alkaline liquids in intraplate continental context. Phase assemblages, proportions, and compositions have been determined on six trachytes with SiO 2 contents varying from 62 to 69 wt % and alkali contents of 10.5-12.0 wt %. The samples contain up to 30 % of phenocrysts, mainly consisting of feldspar (15-17 %; plagioclase and/or alkali-feldspar), biotite (2-6 %; except in the SiO 2 -poorest sample), Fe-Ti oxides (1-3 %) ± amphibole (< 5 %), ± clinopyroxene (~1 %). All samples have apatite and zircon as minor phases and titanite has been found in one sample. Pristine glasses (melt inclusions or residual glasses) in pumice from explosive events are trachytic to rhyolitic (65-73 wt % SiO 2 and 10.5-13.0 wt % alkali). H 2 O dissolved in melt inclusions and the biotite+alkali feldspar+magnetite hygrobarometer both suggest pre-eruptive H 2 O contents up to 8 wt %. These are so far the highest H 2 O contents ever reported for alkaline liquids in an intraplate continental context. Melt inclusions also contain ~3400 ppm chlorine, ~700 ppm fluorine, and ~300 ppm sulphur. Crystallisation experiments of the six trachytes have been performed between 200 and 400 MPa, 700 and 900°C, H 2 O saturation, and oxygen fugacity of NNO +1. The comparison between the natural and experimental phase assemblage, proportion, and composition suggests magma storage conditions at a pressure of 300-350 MPa (~10-12 km deep), melt H 2 O content ~8 wt % (close to saturation), an oxygen fugacity close to NNO~0.5, and temperatures increasing from 700 to 825°C with decreasing bulk SiO 2 of the trachyte. The high H 2 O contents of the trachytes show that wet conditions may prevail during the differentiation of continental alkaline series. Regardless of the size of the magma reservoir assumed to have fed the trachyte eruptions, calculation of the thermal relaxation timescales indicates that the tapped reservoir(s) are likely to be still partially molten nowadays. The four northernmost edifices may correspond to a single large reservoir with a lateral extension of up to 10 km, which could be possibly reactivated in weeks to months if intercepted by new rising basalt batches.3 Keywords: trachyte -alkaline seriesphase relationshipspre-eruptive conditions -Chaîne des PuysIn this study, we have acquired new petrological data on the CDP trachytes and we compared them to experimental phase equilibria performed on the same rocks, in order to determine (i) the pre-eruptive conditions of the trachytic reservoirs beneath the CDP volcanoes and (ii) phase relationships in differentiated alkaline series between 200 and 400MPa.

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Estimation of pre-eruptive magmatic water fugacity in the Phlegrean Fields, Naples, Italy

Cited by 11 publications

References 28 publications

Chlorine as a geobarometer for alkaline magmas: Evidence from a systematic study of the eruptions of Mount Somma-Vesuvius

Chlorine as a geobarometer for alkaline magmas: Evidence from a systematic study of the eruptions of Mount Somma-Vesuvius

Multiple magma degassing sources at an explosive volcano

Trachyte Phase Relations and Implication for Magma Storage Conditions in the Chaine des Puys (French Massif Central)

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