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A review of the recent geochemical investigations carried out on products of the Campi Flegrei volcanic field is presented, with particular attention on radiogenic (Sr, Nd, Pb) and stable (B, O) isotope data. The studied volcanic rocks span the entire period of best known Campi Flegrei volcanic field activity, since ~58 ka to the last event, the AD 1538 Monte Nuovo eruption. The isotope data, combined with mineralogical, geochemical, geochronological and volcanological data have allowed reconstructing a complex behaviour of the Campi Flegrei volcanic field magmatic feeding system. They suggest that several, isotopically-distinct magmatic components fed the activity over various time periods. In particular, over the past 15 kyrs at least three isotopically-distinct magmatic components, located either in a deep and large reservoir or in shallower and smaller chambers, have variably interacted, eventually feeding the volcanic activity. These magmatic components originated through a complex interplay of magma supply from a variably-enriched mantle source, and crustal contamination processes occurring at depth. Mingling/mixing among these isotopically-distinct magmatic components, as well as closed-system differentiation of variable hybrid magmas and interaction with cumulate mushes, were the dominant processes acting in the Campi Flegrei caldera feeding system over the past 15 kyrs. Three examples including the Agnano-Monte Spina, Astroni and Averno 2 eruptions of this period are described to illustrate the interplay among the above-mentioned different processes.

Mt. Etna, in Sicily (Italy), produces effusive and explosive eruptions from summit craters and flanks. Petrology of erupted products has proved fundamental to explore the relationship between magma dynamics within the plumbing system and eruptive styles. Data of Sr Nd isotopes are quite scarce if compared with the great number of chemical analyses carried out in products of last decades. We measure Sr Nd isotopes, major and trace elements in products emitted from 2001 to 2012, and consider also published analyses of the 1995–2001 eruptions, because carried out in the same laboratories of 2001–2012 ones. Furthermore, we take into account other published analyses extending back to the 14th century, even if performed by different facilities. Based on this dataset, magma dynamics operating at different timescales inside the volcano's plumbing system have been explored. Our analyses evidence that, from 2001–2012, three magma types are present in the volcano's plumbing system: (i) a deep and poorly evolved basaltic and K-trachybasaltic magma, enriched in radiogenic Sr and LILE, erupted during the 2001 and 2002–03 flank activity; (ii) a shallower more evolved K-trachybasaltic magma, less enriched in radiogenic Sr, feeding both summit and flank eruptions and (iii) an uncommon, and scarcely radiogenic hawaiitic magma, LILE poor, emitted exclusively from a small sector of the 2002–03 eruptive fissures. By considering a broader time scale, from 14th to 21st century, we conclude that: (i) different magmatic components are present in the deep volcano's plumbing system, at about 10–12 km b.s.l; (ii) a decoupling of geochemical and isotopic features in magmas stored at different depths is observed after the 1974 flank eruption up to date; (iii) mixing between different magmas is an efficient magmatic process to produce magma differentiation at Mt. Etna, regardless of the investigated temporal scale.

Somma-Vesuvius is one of the most dangerous active Italian volcanoes, due to the explosive character of its activity and because it is surrounded by an intensely urbanized area. For mitigating the volcanic risks, it is important to define how the Somma-Vesuvius magmatic system worked during the past activity and what processes took place. A continuous coring borehole drilled at Camaldoli della Torre, along the southern slopes of Somma-Vesuvius, allowed reconstructing its volcanic and magmatic history in a previous study. In this work, the wide range of chemical (Mg# = 92–69) and isotopic (87Sr/86Sr = 0.70781–0.70681) compositions, collected on single clinopyroxene crystals separated from selected lava flow units of the Camaldoli della Torre sequence, have been integrated with the already available bulk geochemical and Sr-isotopic data. The detected chemical and isotopic signatures and their variation through time allow us to better constrain the behavior of the volcano magmatic feeding system, highlighting that mixing and/or assimilation processes occurred before a significant change in the eruptive dynamics at Somma-Vesuvius during a period of polycyclic caldera formation, starting with the Pomici di Base Plinian eruption (ca. 22 ka).

We illustrate a quantitative conductive/convective thermal model incorporating a wide range of geophysical, petrological, geological, geochemical and isotopical observations that constrain the thermal evolution and present state of the Campi Flegrei caldera (CFc) magmatic system. The proposed model has been computed on the basis of the current knowledge of: (1) the volcanic and magmatic history of the volcano over the last 44 ka, (2) its underlying crustal structure, and (3) the physical properties of the erupted magmas. 3D numerical simulations of heat conduction and convection within heterogeneous rock/magma materials with evolving heat sources and boundary conditions that simulate magma rise from a deep (≥ 8 km depth) to shallow (2–6 km) reservoirs, magma chamber formation, magma extrusion, caldera collapse, and intra-caldera hydrothermal convection, have been carried out. The evolution of the CFc magmatic system through time has been simulated through different steps related to its changes in terms of depth, location and size of magma reservoirs and their replenishment. The thermal modeling results show that both heat conduction and convection have played an important role in the CFc thermal evolution, although with different timing. The simulated present heat distribution is in agreement with the measured geothermal profiles (Agip, 1987), reproduces the thermal gradient peaks at the CFc margins in correspondence to the anomalies in surface gradients (Corrado et al., 1998), and suggests temperatures of 700 °C at depth of 4 km in the central portion of the caldera, in agreement with the estimated temperature for the brittle-ductile transition (Hill, 1992 ).

Plinian eruptions are characterized by high intensity and an overall steady character, and result in a stable convective column. The main processes controlling the dynamics of such steady and stable plume systems have been extensively investigated. Conversely, sub-Plinian eruptions are unsteady, as recorded by the large variability of the products and deposits. Our knowledge of the processes creating this unsteadiness on various timescales remains limited, and still requires more observations as well as theoretical and experimental investigation. Here, we focus on the sub-Plinian eruption of the Greenish Pumice (GP, 19,265 ± 105 BP), Mt. Somma-Vesuvius (Italy). On the basis of coupled geochemical and textural analyses of samples from the well-established stratigraphy of the GP deposits, we investigate volatiles (H2O, CO2, F, Cl) to better constrain the unsteady sub-Plinian eruptive style. This allows us to carry out a detailed study of the degassing processes in relation to the eruption dynamics. We find that degassing by open-system processes generally dominates throughout the entire eruption, but alternates with episodes of closed-system degassing. The fluctuating degassing regimes, responsible for the variable magma ascent rate within the conduit, are also responsible for the eruptive column instability. Volatile behavior is well correlated with textural heterogeneities of the eruptive products. Both reflect higher conduit heterogeneity than for Plinian eruptions, where we find a higher horizontal gradient in magma ascent velocity due to a smaller conduit diameter.

The increasing application of cryptotephra studies is leading the identification of new tephra marker layers the sources of which in many cases may not be known or may be ambiguous. In this contribution, we discuss the controls on tephra geochemistry in the context of establishing the provenance of an unknown tephra layer. We use the RESET database ( https://c14.arch.ox.ac.uk ), which contains major and trace element data for a number of European silicic tephra erupted in the period 100 ka to ca 10 ka, to define new and modify existing tectonic setting discrimination diagrams for use with volcanic glass analyses. Bivariate plots of the elements Rb, Nb, Ta, Y and Th and K 2 O, SiO 2 , FeO and MgO can be used to identify tephra from different tectonic settings. New, detailed glass chemistry shows that tephra from the productive Neapolitan volcanic centres, Somma-Vesuvius (22–4 ka activity), Campi Flegrei (60–15 ka) and Ischia (75–20 ka), can be separated using major elements, CaO–SiO 2 , Na 2 O/K 2 O–CaO and CaO–MgO. In each of these centres, the tephrostratigraphic record is characterized by the repeated occurrence of similar glass compositions, punctuated by significant changes in magma chemistry. The glass compositions of successive eruptions from Campi Flegrei are similar but there is a significant change in the composition following the Campanian Ignimbrite, and there are comparable compositional changes at Ischia following the Monte Epomeo Green Tuff eruption and at Somma-Vesuvius following the Verdoline event. Distinguishing different tephras from a single volcanic centre is more problematic, and in some instances even impossible, without good chronological and stratigraphic control and/or high-resolution trace element glass data. At Somma-Vesuvius certain major elements can be used to separate glasses from the major chronological phases (Group 1 – Pomici di Base and Verdoline; Group 2 – Mercato and Avellino), but separating tephras within a single group on the basis of glass composition can be problematic.

Tephra layers from six deep-sea cores, recovered between the Ionian and the Aegean Seas, and covering a time span between ~ 102 and ~ 8.2 ka BP, were investigated with the aim of identifying their volcanic source. The stratigraphic position of each tephra layer defined by means of nannofossil biostratigraphy and occurrence of sapropel layers was integrated with a thorough geochemical characterization of glass shards based on major oxides and trace elements content, and Sr-Nd isotope ratios. Major oxides composition permitted their subdivision into three groups (K-trachyte, peralkaline rhyolite, andesite), confirmed by Principal Component Analysis on trace elements data. Primordial mantle-normalized trace elements distribution patterns allowed for precise identification of the geochemical affinity and geodynamical setting of each group. Although the Sr isotopic composition of some investigated tephras was deeply affected by seawater alteration as expected, the 143 Nd/ 144 Nd values discriminate well the three groups of tephras in combination with major oxides and trace elements data. Therefore, La/Yb and Th/Y vs. 143 Nd/ 144 Nd discrimination diagrams are proposed for identification of potential volcanic sources active in the 102–8.2 ka BP time span in the Eastern Mediterranean area for unknown tephras. The obtained results have permitted the attribution of six K-trachytic tephras to the Y-5 stratigraphic marker (Campanian Ignimbrite eruption of Campi Flegrei, Southern Italy, ~ 39 ka BP), and two pantelleritic (= peralkaline rhyolite) tephras to the Y-6 stratigraphic marker (Green Tuff eruption of Pantelleria Island, Sicily Channel, ~ 46 ka BP). The andesitic tephra, stratigraphically constrained between ~ 39 and ~ 83–102 ka BP, might correspond to the X-1 stratigraphic marker, found in several deep-sea cores of the Eastern Mediterranean Sea, although its attribution is still debated in the literature. On the basis of trace elements content, supported by Sr-Nd isotopic features, it is here hypothesized that this tephra could be related to a volcanic source located in the Aegean Sea area, probably the island of Santorini. More generally, this study demonstrates that the combination of Sr-Nd isotopic with major oxide and trace element geochemical fingerprinting on selected and purified glass shards is a very effective tool for identifying nature and source of doubtful tephra layers.

[1] We present an improved density model and a new structural map of the Neapolitan Yellow Tuff caldera, the active portion of the nested Campi Flegrei caldera. The model was built using a new 3-D inversion of the available high-precision gravity data, and a new digital terrain and marine model. The inversion procedure, based on a variable-depth lumped assembling of the subsurface gravity distribution via cell aggregation, gives better defined insights into the internal caldera architecture, that well agree with the available geological, geophysical, and geochemical data. The adopted 3-D gravity method is highly efficient for characterizing the shallow caldera structure (down to 3 km depth) and defining features related to regional or volcano tectonic lineaments and dynamics. In particular, the resulting density distribution highlights a pronounced density low in correspondence of the central portion of the caldera with a detail not available till now. The joint interpretation of the available data suggests a subsurface structural setting that supports a piecemeal collapse of the caldera, and allows the identification of its headwall. Positive gravity anomalies localize dense intrusions (presently covered by late volcanic deposits) along the caldera marginal faults, and the main structural lineaments both bordering the resurgent block and cutting the caldera floor. These results allow us to both refine the current geological-structural framework and propose a new structural map that highlights the caldera boundary and its internal setting. This map is useful to interpret the phenomena occurring during unrest, and to improve both short-term and long-term volcanic hazards assessment.

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.

Mt. Etna volcano is located in a complex tectonic setting, with large sectors of its eastern flank sliding seaward at different rates. According to recent petrologic studies, the Etna's plumbing system has a multifaceted geometry, variable in space and time and consisting of storage zones at different depths, where magma ascending to the surface undergoes various processes, mainly fractional crystallization and mixing. In this framework we investigated a possible cause–effect relationship between the flank displacement and pre-eruptive magmatic processes in the shallow plumbing system ( Furthermore, a comparison between petrologic data and deformative patterns evidences that, from 1995 to July 2001, the aforementioned pre-eruptive magmatic processes did not significantly influence the volcano eastern flank dislocation, which stayed slow and fairly regular. By contrast, the onset of the 2001 flank eruption leads to an acceleration of the movement as a consequence of the ascent, of a primitive, volatile-rich, sub-aphyric basaltic magma from a deeper (about 10 km b.s.l.) reservoir, during the 2001 and 2002–03 activity. At least for the decade 1995–2005, pre-eruptive magmatic processes in the shallow portion (

Barium diffusion chronometry applied to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (∼4.7 ka) constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera. Backscattered electron imaging and quantitative electron microprobe measurements on 50 sanidine phenocrysts from representative pumice samples document core-to-rim compositional zoning. We focus on compositional breaks near the crystal rims that record magma mixing processes just prior to eruption. Diffusion times were modeled at a magmatic temperature of 930 °C using profiles based on quantitative BaO point analyses, X-ray scans, and grayscale swath profiles, yielding times ≤60 years between mixing and eruption. Such short timescales are consistent with volcanological and geochronological data that indicate that at least six eruptions occurred in the Agnano-San Vito area during few centuries before the Agnano-Monte Spina eruption. Thus, the short diffusion timescales are similar to time intervals between eruptions. Therefore, the rejuvenation time of magma residing in a shallow reservoir after influx of a new magma batch that triggered the eruption, and thus pre-eruption warning times, may be as short as years to a few decades at Campi Flegrei caldera.

Geochemical and isotopic ( 87 Sr/ 86 Sr and 18 O/ 16 O) data have been acquired on whole rock and separated mineral samples from volcanic products of the 1302 AD Arso eruption, Ischia volcanic island (Gulf of Naples, Southern Italy), to investigate magmatic processes. Our results highlight petrographic and isotopic disequilibria between phenocrysts and their host rocks. Similar disequilibria are observed also for more mafic volcanic rocks from Ischia and in the Phlegraean Volcanic District in general. Moreover, 87 Sr/ 86 Sr and 18 O/ 16 O values suggest mixing between chemically and isotopically distinct batches of magma, and crystals cargo from an earlier magmatic phase. The radiogenic Sr isotope composition suggests that the mantle source was enriched by subduction-derived sediments. Furthermore, magmas extruded during the Arso eruption were affected by crustal contamination as suggested by high oxygen isotope ratios. Assimilation and fractional crystallization modelling of the Sr-O isotope compositions indicates that not more than ~ 7% of granodioritic rocks from the continental crust have been assimilated by a mantle-derived mafic magma. Hence the recent volcanic activity of Ischia has been fed by distinct batches of magma, variably contaminated by continental crust, that mixed during their ascent towards the surface and remobilized phenocrysts left from earlier magmatic phases.

To develop a model of both the structure and evolution of the Campi Flegrei caldera (CFc) magmatic feeding system, geochronological, geochemical and Sr, Nd, Pb and B isotopic data of representative volcanic products of the past 15 ka have been combined with geophysical and melt inclusion literature data, structural setting and dynamics of the resurgent caldera. According to previous petrological data, the CFc magmatic feeding system consists of a deep reservoir, in which mantle-derived K-basaltic parental magmas differentiate to shoshonite, latite and trachyte, through combined crustal contamination and fractional crystallization processes, and shallow reservoirs where the evolved magmas further differentiate and mingle/mix before eruptions. The Sr, Nd, Pb, and B isotope data allow recognition of three distinct magmatic components. One component is believed to be residual magma from the Neapolitan Yellow Tuff (NYT) caldera forming eruption. The NYT component (87Sr/86Sr of 0.70750–53, 143Nd/144Nd ratio of ca. 0.51246, 206Pb/204Pb of ca. 19.04 and δ11B of ca. –7.9‰), has been the most prevalent component over the past 15 ka being mixed, in most cases, with the other two components. One of these other components is best recognized in the Minopoli 2 magma, first erupted 10 ka ago. Minopoli 2 magma is shoshonitic in composition and is the most enriched in radiogenic Sr (87Sr/86Sr of ca. 0.70860) and unradiogenic Nd and Pb (143Nd/144Nd ratio of ca. 0.51236, 206Pb/204Pb of ca. 18.90), and is characterised by δ11B value of ca. –7.32‰. The third component is trachytic in composition and has higher 206Pb/204Pb (ca. 19.08), lower 87Sr/86Sr (ca. 0.70726) and δ11B (−9.8‰) and higher 143Nd/144Nd (ca. 0.51250), with respect to the NYT component. This third component is best recognized in the Astroni 6 magma and did not appear until ca. 4 ka. The identified isotopically distinct magmatic components were erupted in different sectors of the CFc. During both I (

On 27 February 2007, at 12.49 GMT, a new eruption of Stromboli took place with the effusion of a lava flow from a fracture cutting the flank of the NE cone, which rapidly reached the sea. The eruption had been heralded by an increase in the amplitude of tremor and flank movement since at least the 14th of February. Short-term precursors were an increase in the rate of occurrence of small landslides within the “Sciara del Fuoco” scar on the North-western flank of the volcano. A new effusive vent opened at 18.30 GMT on the Sciara del Fuoco at an height of 400 m asl. The new lava emission caused the sudden termination of the summit flow and initiated a period of non-stationary lava outpouring which ended on 2 April, 2007. The eruption has been characterized by a rapid decrease in the eruption rate after the first days and subsequently by episodic pulse increases. On the 15th of March, the increase in lava outpouring, monitored by a thermal camera, heralded by 9 min the occurrence of a violent paroxysmal explosion with the formation of an impulsive eruption column and the emission of small pumices mingled with black scoriae. The pumice had a bulk composition similar to that of the lava and of the black scoriae, but with a distinct lower content of phenocrysts. A similar feature has been repeatedly observed during the major explosive paroxysms of Stromboli. Short term precursors of the paroxysm were recorded by strainmeter and tiltmeter stations. The volcano monitoring activity has been made by a joint team of researchers from the INGV sections of Catania, Napoli, Palermo and Rome, along with researchers from the Universities of Florence, Pisa, Roma Tre, and Palermo. The scientific activity was coordinated by a Synthesis Group made up by scientists responsible for the different monitoring techniques of INGV and Universities and by the volcanic experts of Commissione Nazionale Grandi Rischi of the Prime Minister Office (Civil Protection Department). The group made a daily evaluation of the state of the volcano and transmitted its recommendations to the Civil Protection Department (DPC). Several prevention measures were adopted by DPC, the main of which were the evacuation of the coast zone when strong acceleration of the Sciara del Fuoco slope motion (occurred twice) could led to a dangerous tsunami by flank collapse (as last occurred on 30 December 2002) and four days before the 15 March paroxysm when access was prohibited to the part of the volcano above 290 m asl.

Following the 2001 and 2002–2003 flank eruptions, activity resumed at Mt. Etna on 7 September 2004 and lasted for about 6 months. This paper presents new petrographic, major and trace element, and Sr–Nd isotope data from sequential samples collected during the entire 2004–2005 eruption. The progressive change of lava composition allowed defining three phases that correspond to different processes controlling magma dynamics inside the central volcano conduits. The compositional variability of products erupted up to 24 September is well reproduced by a fractional crystallization model that involves magma already stored at shallow depth since the 2002–2003 eruption. The progressive mixing of this magma with a distinct new one rising within the central conduits is clearly revealed by the composition of the products erupted from 24 September to 15 October. After 15 October, the contribution from the new magma gradually becomes predominant, and the efficiency of the mixing process ensures the emission of homogeneous products up to the end of the eruption. Our results give insights into the complex conditions of magma storage and evolution in the shallow plumbing system of Mt. Etna during a flank eruption. Furthermore, they confirm that the 2004–2005 activity at Etna was triggered by regional movements of the eastern flank of the volcano. They caused the opening of a complex fracture zone extending ESE which drained a magma stored at shallow depth since the 2002–2003 eruption. This process favored the ascent of a different magma in the central conduits, which began to be erupted on 24 September without any significant change in eruptive style, deformation, and seismicity until the end of eruption.

We present new electron microprobe and Sr-isotope analytical results from mixing experiments using natural volcanic samples. In order to constrain the dynamics of such mixing events, we applied a Taylor–Couette flow, simulating forced convection under very low Reynolds numbers, in a time series ranging from 1 h up to 1 week. The end-member melts derive from samples of the Campanian Ignimbrite (CI), in Italy. The CI is thought to represent a layered reservoir formed in 3 stages: 1) a resident phono-trachytic magma reservoir (end-member A); replenished by 2) a less evolved trachybasaltic–trachytic magma (end-member B of trachytic composition); 3) short-term pre-eruptive mixing in the shallow chamber between a new trachytic and the phono-trachytic resident magmas. Our experiments are motivated by this hypothesis. The two end-members are stirred together, under constant low flow velocity (0.5 rotations per minute). This initially generates single convection cells, which cause progressive homogenization of some major components. This is the case after 1, 4 and 9 h. After 16 h the 87Sr/86Sr-isotopic system is homogenized and the starting compositions are fully mixed. Then separate convection cells and compositional layering for major and minor elements emerged. Based on microprobe measurements of quenched melts (glass) from the 16-hour, 25-hour and 1-week long experiments, we confirm the separation of layers having different densities. This phenomenon is locally complicated by the production of micro-volumes of unmixed melts. Our results support the effectiveness of the interplay between convection and diffusion, enhanced by a double-diffusive–convection-driven differentiation for moderately high-silica magmas under high (near-liquidus) temperatures, attesting that differentiation initiates in the liquidus before the onset of fractional crystallization.

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.

A continuous-coring borehole recently drilled at Camaldoli dellaTorre on the southern slopes of Somma^Vesuvius provides constraints on the volcanic and magmatic history of the Vesuvian volcanic area since c. 126 ka BP. The cored sequence includes volcanic units, defined on stratigraphical, sedimentological, petrological and geochemical grounds, emitted from both local and distal vents. Some of these units are of known age, such as one Phlegraean pre-Campanian Ignimbrite, Campanian Ignimbrite (3 9 ka), Neapolitan Yellow Tuff (14 ?9 ka) and Vesuvian Plinian deposits, which helps to constrain the relative age of the other units. The main rock types encountered are shoshonite, phonotephrite, latite, trachyte and phonolite. The seque nce includes, from the base upwards: a thick succession of pyroclastic units emplaced between 126 and 3 9 ka, most of them attributed to eruptions that occurred in the Phlegraean area; the Campanian Ignimbrite; the products of a local tuff cone formed between 3 9 ka and the deposition of the products of the earliest activity of the Mt. Somma volcano; the products of the Somma^Vesuvius volcano, which include from the base upwards a thick sequence of lavas, pyroclastic rocks and the products of a local spatter cone dated between 3 ?7 ka and AD 79.The data obtained from the study of the borehole show that, before the Campanian Ignimbrite eruption, low-energy explosive volcanism took place in the Vesuvian area, whereas mostly high-energy explosive eruptions characterized the Campi Flegrei activity. In the Vesuvian area, Campanian Ignimbrite deposition was followed by the eruption of a local tuff cone and a long repose time, which predated the formation of the Mt. Somma edifice. Since 18 ?3 ka (Pomici di Base eruption) the activity of Somma^Vesuvius became mostly explosive with rare lava effusions. The shallowest cored deposits belong to the Camaldoli dellaTorre cone, formed between the Pomici di Avellino and Pomici di Pompei eruptions (3 ?7 ka^AD 79). New geochemical and Sr^Nd^Pb^ B-isotopic data on samples from the drilled core, together with those available from the literature, allow us to further distinguish the volcanic rocks as a function of both their provenance (i.e. Phlegraean or Vesuvian areas) and age, and to identify different magmatic processes acting through time in the Vesuvian mantle source(s) and during magma ascent towards the surface. Isotopically distinct magmas, rising from a mantle source variably contaminated by slab- derived components, stagnated at mid-crustal depths (8^10 km below sea level) where magmas differentiated and were probably contaminated. Contamination occurred either with Hercynian continental crust, mostly during the oldest stages of Vesuvian activity (from 3 9 to 16 ka), or with Mesozoic limestone, mostly during recent Vesuvian activity. Energy constrained assimilation and fractional crystallization (EC-AFC) modelling results show that contamina- tion with Hercynian crust probably occurred during differentiation from shoshonite to latite. Contamination with limestone, which is not well constrained with the available data, might have occurred only during the transition from shoshonite to tephrite. From the 'deep' reservoir, magmas rose towards a series of shallow reservoirs, in which they differentiated further, mixed, and fed volcanic activity.

Boron concentration and isotopic compositions were determined in representative products from the Phlegrean Volcanic District (PVD), which includes Campi Flegrei (CF), and the islands of Procida and Ischia. The most primitive products (from Procida and Ischia islands) are moderately enriched in B (4.6-12 ppm), whereas more evolved products of CF and Ischia Island are more enriched (21-118 ppm). The content of B is positively correlated with Nb, Zr, Th, La and, generally, with all incompatible elements. delta11B values are generally lower and more uniform in samples from CF (-6.8 to - 10.6‰) compared with those from Procida (-3.6 to -8.5‰) and Ischia (-2.8 to -8.4‰) islands. Overall, B-enrichments relative to fluid-immobile elements of PVD are only slightly higher than those observed in mid-ocean ridge basalts and there is no significant correlation between delta11B and B/immobile element ratios. For CF samples including the Campanian Ignimbrite (CI) and most post-CI products, delta11B is negatively correlated with 87Sr/86Sr, with extreme compositions represented by evolved products of the CI (higher delta11B, lower 87Sr/86Sr) and less evolved shoshonite (lower delta11B, higher 87Sr/86Sr). In contrast, samples from Procida, Ischia, and pre-CI products and one young shoshonite from CF define a distinct correlation with primitive trachybasalt as the high delta11B, low 87Sr/86Sr end-member, and young shoshonites as the low delta11B, high 87Sr/86Sr end-member. The overall interpretation of the geochemical and isotopic data suggests three conclusions: (1) Geochemical and isotopic variations of post-CI products from CF can be explained by mixing/mingling between at least two distinct magmas, i.e. the CI and the young shoshonite (Minopoli 1). (2) The isotopic trend described by Procida trachybasalts, Ischia samples, pre-CI samples from CF and Pigna St. Nicola shoshonite is a mantle trend suggesting the involvement in their genesis of a distinct component depleted in B, with low delta11B and high 87Sr/86Sr. A similar component has been invoked to explain the differences between Stromboli potassic lavas and more typical calc-alkaline rocks of the Aeolian Islands. This component is consistent with ‘sediments or melts thereof' introduced into the mantle by subduction, but depleted in B due to metamorphic reactions accompanying subduction. (3) The displacement from the mantle trend of CI and Minopoli 1 shoshonite magmas is probably due to crustal contamination processes.

Sr-isotopic microanalysis has been performed on selected minerals from the Campi Flegrei caldera, together with Sr and Nd isotopic ratio determinations on bulk mineral and glass fractions. The aim was a better characterization of the chemically homogeneous, but isotopically distinct magmatic components which fed volcanic eruptions of the caldera over the past 5 ka, in order to enhance our knowledge about one of the most dangerous volcanoes on Earth. Information on the involved magmatic endmembers, unobtainable by analyzing the isotopic composition of whole rock samples and bulk mineral fractions, has been acquired through high-precision determination of 87 Sr/ 86 Sr on single crystals and microdrilled mineral powders. We focused our investigations on the products emplaced during the Astroni 6 eruption (4.23 cal ka BP), assumed representative of the expected event in case of renewed volcanic activity in the Campi Flegrei caldera. Data on single crystals and microdrilled mineral powders have been compared with Sr and Nd isotopic compositions of bulk mineral fractions from products emplaced during the whole Astroni activity, which included seven distinct eruptions. The 87 Sr/ 86 Sr ratios of single crystals and microdrilled mineral powders are in the 0.7060 to 0.7076 range, much wider than that of bulk mineral fractions, which range from 0.7066 to 0.7076. Moreover, the Sr isotopic ratios are inversely correlated to 143 Nd/ 144 Nd. The new data allow us to better define the magmatic endmembers involved in mingling/mixing processes that occurred prior to/during the Astroni activity. One magmatic endmember, characterized by average 87 Sr/ 86 Sr ratio of ~ 0.70750, was quite common in the past 15 ka activity of the Campi Flegrei caldera; the other, as evidenced by the isotopic composition of single feldspar and clinopyroxene crystals, is less enriched in radiogenic Sr ( 87 Sr/ 86 Sr ~ 0.70724). The latter is interpreted to represent a new magmatic component that entered the Campi Flegrei caldera feeding system in the past 5 ka, the previously recognized Astroni 6 component. However, diopside crystals in Astroni 6 are characterized by even lower 87 Sr/ 86 Sr, in the range of 0.7060–0.7068 and by the highest 143 Nd/ 144 Nd ratios measured in the products of Astroni activity. These diopsides may represent another common magmatic component, as they have been found in most of the Phlegrean Volcanic District products emplaced over the past 75 ka. These diopsides, crystallized in a mantle-derived mafic magma, were entrapped by the Astroni 6 magma during ascent, before it mingled/mixed with the more differentiated and enriched in radiogenic Sr resident magma, thus attaining an intermediate Sr-Nd isotopic fingerprint. These results have an important outcome on the understanding of the volcano behavior, as renewed activity can be triggered by the arrival of fresh magma in the feeding system that would mingle/mix with the resident magma. Such an event may be able to start an unrest phase at the volcano that could last for years or decades, perhaps culminating in a new eruption.

New geochemical and isotopic data on volcanic rocks spanning the period ~75–50 ka BP on Ischia volcano, Italy, shed light on the evolution of the magmatic system before and after the catastrophic, caldera-forming Monte Epomeo Green Tuff (MEGT) eruption. Volcanic activity during this period was influenced by a large, composite and differentiating magmatic system, replenished several times with isotopically distinct magmas of deep provenance. Chemical and isotopic variations highlight that the pre-MEGT eruptions were fed by trachytic/phonolitic magmas from an isotopically zoned reservoir that were poorly enriched in radiogenic Sr and became progressively less radiogenic with time. Just prior to the MEGT eruption, the magmatic system was recharged by an isotopically distinct magma, relatively more enriched in radiogenic Sr with respect to the previously erupted magmas. This second magma initially fed several SubPlinian explosive eruptions and later supplied the climactic, phonolitic-to-trachytic MEGT eruption(s). Isotopic data, together with erupted volume estimations obtained for MEGT eruption(s), indicate that >5–10 km3 of this relatively enriched magma had accumulated in the Ischia plumbing system. Geochemical modelling indicates that it accumulated at shallow depths (4–6 km), over a period of ca. 20 ka. After the MEGT eruption, volcanic activity was fed by a new batch of less differentiated (trachyte-latite) magma that was slightly less enriched in radiogenic Sr. The geochemical and Sr–Nd-isotopic variations through time reflect the upward flux of isotopically distinct magma batches, variably contaminated by Hercynian crust at 8–12 km depth. The deep-sourced latitic to trachytic magmas stalled at shallow depths (4–6 km depth), differentiated to phonolite through crystal fractionation and assimilation of a feldspar-rich mush, or ascended directly to the surface and erupted.

International audience; The 2007 caldera-forming eruption of Piton de la Fournaise (PdF) erupted the largest volume of magma (210 Mm3) recorded at this volcano in at least three centuries. Major and trace element and Sr–Nd isotope data for bulk-rocks, groundmasses and olivine phenocrysts have been combined with melt inclusion data (major, trace and volatile elements) to track magma evolution over the whole eruptive sequence. We show that each eruptive phase had a distinctive geochemical and petrological signature and that caldera collapse on 5 April was preceded by a marked shift in bulk magma composition and crystal content and size. Aphyric basalt erupted at the beginning of the sequence (February 2007) had relatively high Sr isotope ratio (87Sr/86Sr = 0·70420–0·704180) and low Nd isotopic ratio (143Nd/144Nd = 0·51285–0·51286). Olivine-basalts extruded on 2–5 April just before caldera collapse are less enriched in radiogenic Sr (87Sr/86Sr = 0·70412–0·70416), but characterized by the same Nd isotopic composition. This magma is interpreted as a new deep input, which pressurized the shallow PdF plumbing system and triggered the 2007 activity. Post-collapse oceanite lavas represent the main volume of magma extruded in 2007. Their bulk-rocks and groundmasses have 87Sr/86Sr (∼0·70418) intermediate between those of February and 5 April, and similar to those of the March 2007 and 2001–2006 lavas. We show that the Steady State Basalts (SSB) commonly erupted at PdF are hybrid melts, which result from multistep mixing between ‘alkaline’ and ‘transitional’ end-members. Our results lead us to propose a new model of the PdF plumbing system to reconcile the petrological, geochemical and geophysical observations: (1) the shallow portion (above sea level) of the PdF plumbing system hosts several small sills, in which magma experiences variable degrees of degassing, cooling and crystallization; (2) oceanite lavas result from the withdrawal of shallow harrisitic mushes stored at low pressures (

Major, trace element and Sr-Nd-isotopic data on mafic volcanic rocks with shoshonitic affinity from the islands of Procida and Ventotene (Campanian Region, South Italy) are reported. Within-suite chemical and isotopic variations are interpreted in terms of open system differentiation processes held responsible for enrichment in a number of trace elements and for radiogenic Sr observed in both Procida and Ventotene volcanic sequences. Conversely, trace element contents and Sr-Nd-isotopic compositions of the least-evolved among the investigated samples are thought to reflect source region characteristics with only negligible crustal contamination of the primary magmas. The data support an origin from distinct source regions for the primary magmas. In the case of Ventotene, the source would have been asthenospheric and/or lithospheric mantle with features similar to transitional mid-ocean ridge basalts (T-MORB), modified by enriching agents made up mainly of subducted slab-released components coming from marly sediments (about 7%) similar to cherts from Tuscan Apennines plus a limestone contribution. In the case of Procida, the source would have been asthenospheric and/or lithospheric mantle with a slightly more enriched T-MORB-like feature with respect to Ventotene, modified by slab-derived enriching agents, likely represented by a small amount of sediments (about 2.5%) of oceanic nature (mostly terrigenous/pelagic). These differences are constrained by lower Zr/Nb, Y/Nb, Sc/Nb, V/Nb, LILE/HFSE, LREE/HFSE and87Sr/86Sr, higher Ba/La and143Nd/144Nd ratios, as well as by the lack of a detectable negative Eu anomaly, in the least-evolved volcanic rocks of Procida, with respect to those of Ventotene, which show conversely a significant negative Eu anomaly. Thus, a sharp heterogeneity exists in the mantle beneath the Campanian Region. It is thought to be the consequence of two different slabs which are in contact along the Volturno River Plain tectonic line: a continental slab, seismically inactive, descending beneath the Latium Region, and an oceanic slab, seismically active, descending beneath the Calabria, up to the Campanian Region.

The Agnano–Monte Spina tephra (AMST), dated at 4100 years BP by 40 Ar / 39 Ar and 14 C AMS techniques, is the product of the highest-magnitude eruption in the Campi Flegrei caldera (CFc) during its last epoch of activity (4800–3800 years BP). The sequence alternates magmatic and phreatomagmatic pyroclastic-fallout, -flow and -surge beds and bedsets. Two main pumice-fallout deposits with variable easterly-to-northeasterly dispersal axes are about 10 cm thick at 42 km from the vent area. High particle concentration pyroclastic currents were confined to the caldera depression; lower concentration flows overtopped the morphological boundary of the caldera and traveled at least 15 km over the surrounding plain. The unit is subdivided into six members, named A through F in stratigraphic sequence, based upon their sedimentological characteristics. Isopachs and isopleths maps suggest a vent location in the Agnano plain. A volcano-tectonic collapse begun during the course of the eruption, took place along the faults of the northeastern sector of the resurgent block within the CFc, and generated the Agnano plain. The early erupted trachytic magma had a homogeneous alkali–trachytic composition, whereas later-erupted magma shows small-scale hetereogeneities. Trace elements and Sr-isotope compositions, indicate that two isotopically distinct magmas, one alkali–trachytic and the other trachytic, were tapped and partially mixed during the eruption. The small volume (1.2 km3 DRE) of erupted magma and the structural position of the vent suggest that the eruption was fed by a dyke intruded along a normal fault in the sector of the resurgent block under a tensional stress regime.

New geochronological, geochemical, and Sr-isotopic data on volcanics erupted before the Campanian Ignimbrite (CI, 37 ka) and the Neapolitan Yellow Tuff (NYT, 12 ka) caldera-forming eruptions at Campi Flegrei (CF) have allowed us to investigate the behavior and temporal evolution of the Phlegraean magmatic system. The most prominent feature of the CF magmatic system was the existence of a large, trachytic magma chamber, episodically recharged, which fed eruptions for tens of thousands years before the CI and NYT eruptions. During the pre-CI caldera activity, magmas were episodically erupted from vents located outside the present caldera structure. These magmas ranged in composition from trachyte to alkali-trachyte, with Sr-isotope ratios increasing through time, and becoming identical to that of the CI magma, at about 44 ka ago. This suggests that the Phlegraean magmatic system before the CI eruption was acting as an open system. It was being progressively replenished by new batches of magma that mixed with the resident less radiogenic, fractionating trachytic magmas and was periodically tapped. The magma chamber evolution culminated in the catastrophic eruption of the voluminous (150 km3 DRE), chemically and isotopically zoned CI trachytic magmas, and in the resultant CI caldera formation. Subsequent to the CI eruption, during a period of moderate subaereal volcanic activity of about 20 ka duration, magmas predominantly trachytic to alkali-trachytic in composition and isotopically similar to the last emitted CI magma were erupted from vents located inside the CI caldera. The temporal trend shown by Sr-isotope ratios provides evidence for a new input of alkali-trachytic magma, at ca. 15 ka, with 87 Sr / 86 Sr ratio identical to that of the alkali-trachytic magma feeding the first phase of the NYT eruption. These data testify to the arrival in a short time span of a new trachytic to alkali-trachytic magma in the system, isotopically distinct from the CI magma, that gave rise about 3 ka later to eruption of the NYT (40 km3 DRE).

A series of 2-D conductive/convective numerical models show a rather limited range of possible magma chamber configurations that predict the present thermal regime at Campi Flegrei. These models are calculated by HEAT, which allows continuous adjustment of heterogeneous rock properties, magma injection/replenishment, and convective regimes. The basic test of each model is how well it reproduces the measured thermal gradients in boreholes at Licola, San Vito, and Mofete reported by AGIP in 1987. The initial and boundary conditions for each model consists of a general crustal structure determined by geology and geophysics and major magmatic events: (1) the 37 ka Campanian Ignimbrite; (2) smaller volume 37–16 ka eruptions; (3) the 12 ka Neapolitan Yellow Tuff; (4) recent magmatism (e.g., Minopoli at ∼10 ka and Monte Nuovo in 1538 AD). While magma chamber depth is well constrained, magma chamber diameter, shape, volume, and peripheral convective regimes are poorly known. Magma chamber volumes between 200 and 2000 km3 have been investigated with cylindrical, conical (funnel-shaped), and spheroidal shapes. For all reasonable models, a convective zone, developed above the magma chambers after caldera collapse, is necessary to achieve the high gradients seen today. These models should help us understand recent bradyseismic events and future unrest.

New geochemical and Sr-isotope data have been acquired on samples representative of volcanic units erupted inside the resurgent Campi Flegrei caldera (CFc) over the past 12 ka. These data, integrated with previous published petrological, and with newly acquired geochronological, volcanological and geothermal data, shed light on the nature and timing of the processes that controlled the evolution of the Phlegraean magmatic system. In the past 12 ka, three isotopically and geochemically distinct magmatic components were erupted at the CFc as either homogeneous or mixed magma batches. One component, Campanian Ignimbrite component (CIc) ( 87 Sr / 86 Sr =0.70735–0.70740), is similar to the trachytic magma extruded during the first phase of the Campanian Ignimbrite (CI) eruption (37 ka). A second component, Neapolitan Yellow Tuff component (NYTc) ( 87 Sr / 86 Sr =0.70750–0.70757), is similar to the latitic–alkali–trachytic magma batches extruded during the course of the Neapolitan Yellow Tuff (NYT) eruption (12 ka). A third component, Minopoli component (MIc) ( 87 Sr / 86 Sr ≈0.7086), is similar to the trachybasaltic magma of the Minopoli 2 (MI) eruption (9.7 ka). These components were erupted as either single batches of magma, or mixed CI–NYT or MI–NYT batches of magma, through vents located either along the structural boundary of the NYT caldera or inside the NYT caldera, mainly on portions of the resurgent block under extensional stress. The CI and NYT components represent residual portions of older, large-volume magma reservoirs which have fed eruptions since about 60 and 15 ka, respectively. The least-evolved MI component was erupted only during the 12–9.5 ka and 8.6–8.2 ka epochs of activity, through vents located on a NE–SW regional fault system. This component could represent a deeper reservoir tapped by the NE–SW regional fault system reactivated after the NYT caldera collapse. Deeper MI and shallower CI and NYT magmatic systems interacted by mixing among batches of magma during their rise to surface. Overall, the data suggest that the CFc magmatic system today is characterized by the presence of two larger, independent reservoirs, filled by residual portions of the CI and NYT magmas. These generated many smaller, shallower pockets of evolved magma, that fed most of the eruptions that occurred in the CFc over the past 12 ka. Moreover, a deeper reservoir (MI), tapped by the NE–SW regional fault system, provided batches of less-evolved magma that mixed with magma present in the shallower pockets.

The major, trace (including rare earth) element abundances, and Sr-Nd-Pb isotopic compositions, have been analysed for andesitic basalt and andesitic sills and lavas of the Jurassic Ferrar Magmatic Province, Prince Albert Mountains, Antarctica. The typical “crustal signature” of the Ferrar magmatism, characterized by relatively high SiO2, LREE and LILE contents in these samples, is associated with high 87Sr/86Sr and low 143Nd/144Nd. Systematic correlations of major and trace elements indicate that fractional crystallization was important. However, increases in incompatible elements are positively correlated with initial 87Sr/86Sr, suggestive of crustal assimilation processes. The observed correlations between initial 87Sr/86Sr and LREE enrichments have been modelled by an AFC process, starting from the least evolved sample and assuming the compositions of the orthogranulites of Victoria Land as contaminants. The REE patterns of the least evolved Ferrar rocks approach those of E-type MORB, differing only by higher LREE/IREE. The enrichment in LREE, accompanying high initial 87Sr/86Sr, 207Pb/204Pb and low 143Nd/144Nd compared with E-type MORB, can be explained by interaction of “primary Ferrar basalt” with crystalline basement. We propose a petrological model whereby Ferrar magmas were generated through high degrees of melting of an E-type MORB mantle source, and subsequently these “primary” melts underwent AFC processes inheriting a crustal signature. The Sr-Nd-Pb isotopic compositions required by the AFC model for the primary Ferrar basalt are similar to those of the Dupal signature of the oceanic basalts of the Southern Hemisphere (Hart 1984). Transantarctic Mountains would have been located inside the Dupal anomaly in pre-Gondwana dispersion times.

This paper presents the results of an investigation carried out on young volcanic rocks from the Gedemsa and Fanta 'Ale complexes, located in the Main Ethiopian Rift, the site of an intense magmatism since Eocene-Oligocene. The earlier NW-SE direction of extension of the Rift, which generated NE-SW trending faults, rotated around E-W in Quaternary times, and produced the still active N to N-NE Wonji Fault System, The Gedemsa volcano is located in the central part of the Ethiopian Rift, about 100 km SE of Addis Ababa. It is characterized by a wide central caldera, about 8 km in diameter. The general stratigraphic sequence in the area includes, from base upwards, rift-floor ignimbrites, pantelleritic and subordinate trachytic pyroclastic deposits and lava flows and domes, and widespread basaltic deposits. The Fanta 'Ale volcanic complex is located in the northern part of the Main Ethiopian Rift, where the Afar depression begins. It is characterized by a summit caldera of which the diameter is about 4 km. This volcano erupted trachytic and rhyolitic lavas, whereas the most diffuse unit is an ignimbrite related to the caldera collapse. Explosive activity has occurred inside and outside the caldera, forming tuff cones and thick pumice-fallout deposits. The only mafic unit is represented by a basaltic eruption that occurred in 1870 AD. Historical eruptions and intense fumarolic activity are evidence for the persistence activity of the Fanta 'Ale in this part of the Main Ethiopian Rift New geochemical and Sr-Nd-Pb isotope data on representative samples from Gedemsa and Fanta 'Ale volcanoes are presented and discussed in order to shed light on the genesis of mafic and felsic magmas, the genetic link between them, and their possible interaction with the local crust. Volcanic rocks show a typical mafic-felsic bi-modal distribution with few intermediate terms (Daly Gap), as observed at regional scale along the Main Ethiopian Rift as well as on the plateau. Geochemical data and modeling suggest that magmas evolved mainly through fractional crystallization processes, accounting for the entire mafic-felsic compositional variation. However, Sr-Nd-Pb isotope data reveal also open-system evolution processes. The most differentiated, Sr-poor rhyolites suffered important low temperature contamination by shallow fluids of hydrothermal and/or meteoric origin. This affected mostly the Sr isotopic composition of whole-rocks, and much less that of separated feldspars that provide more reliable Sr-87/Sr-86 values. Mafic rocks, as well as the least contaminated felsic rocks, provide evidence for two components involved in the genesis and evolution of mafic magmas: a mantle component, carrying the isotopic composition of the Afar plume, and a crustal component, likely Pan-African sialic lower crust, that might have been added in small amounts, about 2%, to mafic magmas. The origin of the primary magmas is inferred to have occurred by 7% partial melting of a mixed source region including both depleted and enriched mantle components. (C) 2013 Elsevier B.V. All rights reserved.

Petrological and geochemical data are reported for volcanic rocks from Vulcano island. The subaerial volcanism (120 ka to present) built up a NW-SE elongated composite structure, affected by two intersecting multistage calderas. Volcanics older than 20 ka consist mostly of high-K calc-alkaline (HKCA) to shoshonitic (SHO) mafic rocks. These magmas interacted significantly with the continental crust, which generated variable Sr isotopic ratios (0.70412–0.70520). However, a major role was also played by input of parental liquids into the magma chamber, which prevented further evolution of the magmas. HKCA, SHO, and potassic (KS) rocks formed from 20 to 8 ka, display a much larger range of SiO2 (from shoshonites to rhyolites) and higher concentrations of incompatible elements with respect to the previous stage. Sr isotopic ratios show small variations (0.70448–0.70486). Mixing of silicic and mafic liquids and fractional crystallization processes (FC) were the main evolutionary processes during this stage. Volcanics younger than 8 ka consist of SHO and leucite-bearing KS mafic rocks, with abundant intermediate and silicic products. Mafic and intermediate rocks display similar incompatible element abundances and Sr isotopic ratios as the previous stage volcanics, whereas higher 87Sr/86Sr (0.70494–0.70583) are observed in some rhyolites. These products originated from a complex interplay of FC, crustal assimilation, and magma mixing processes. The most mafic rocks show increasing incompatible element abundances, Rb/Sr, Rb/Ba, Mg/Al, Mg/Ca, and a decrease in large ion lithophile to high field strength element ratios, passing from older HKCA-SHO to the younger SHO-KS volcanics. These variations suggest a shifting of magma sources from a slightly metasomatized asthenosphere (fertile peridotite) to a more strongly metasomatized lithospheric mantle (residual peridotite). Time-related petrological and geochemical variations have been used to develop a model for the evolution of the Vulcano plumbing system.

Ischia, one active volcano of the Phlegraean Volcanic District, prone to very high risk, is dominated by a caldera formed 55 ka BP, followed by resurgence of the collapsed area. Over the past 3 ka, the activity extruded evolved potassic magmas; only a few low-energy explosive events were fed by less evolved magmas. A geochemical and Sr–Nd–O isotope investigation has been performed on minerals and glass from products of three of such eruptions, Molara, Vateliero, and Cava Nocelle (

The Neapolitan Yellow Tuff, the product of the largest known trachytic phreatoplinian eruption, gives a good opportunity to investigate the filling mechanisms and internal dynamics of a trachytic magma chamber. A detailed study of the geochemical, mineralogical and isotopical features of the deposit was carried out to investigate the behaviour of the magma chamber before the eruption. The collected data show three distinct compositional groups separated by gaps. Single depositional units contain glass shards formed contemporaneously. Although each of these shards is homogeneous they display the same compositional variations and gaps detected in pumice clasts. This feature is taken as an evidence for interpreting the detected compositional gaps as real gaps in the chamber. Therefore the chamber was filled by three distinct magma bodies separated by compositional gaps. The uppermost magma was alkali-trachyte and highly homogeneous, likely a consequence of vigorous convection. The intermediate magma was trachyte with a slight and continuous compositional variation, likely resulting from less intense convection. The lowermost magma was compositionally zoned from alkali-trachyte to latite downward. This compositional zonation was most likely acquired during uprise from a deeper reservoir. The three magmas entered the chamber sequentially from the uppermost to the lowermost. The latter entered the chamber short before the beginning of the eruption. Its input was interpreted as a possible triggering factor for the eruption. The results of this study strongly support a step-filling mechanism for the Neapolitan Yellow Tuff magma chamber and allow definition of the temporal succession of input of magma batches. Furthermore they also suggest that the magma bodies did not mix although, at least the uppermost two, coexisted inside the chamber for a time long enough to allow internal homogeneization by convection.

The eruptive history of Mt. Somma–Vesuvius is characterised by large explosive events: Pomici di Base eruption (22,030 ± 175 yr cal BP), Mercato (8890 ± 90 yr cal BP), Avellino (3945 ± 10 yr cal BP) and Pompeii (79 AD). Pre-eruptive conditions and sin-eruptive degassing processes of the Avellino eruption, the highest-magnitude Plinian event, have been investigated, using volatile contents (F, Cl, H 2 O) in melt inclusions and residual glass, and textural characteristics of pumice clasts of the 9 fallout layers sampled in detail in a representative sequence. The sequence displays an up-section sharp colour change from white to grey, corresponding to variations in both magma composition and textural characteristics. The pre-eruptive conditions have been constrained by systematic measurements of Cl content in both melt inclusions and matrix glass of pumice clasts. The pumice glass composition varies from Na-rich phonolite (white pumice) to K-rich phonolite (grey pumice). The measured Cl values constantly cluster at 5200 ± 400 ppm (buffer value), whatever the composition of the melt, suggesting that the entire magma body was saturated with sub-critical fluids. This Cl saturation constrains the pre-eruptive pressures and maximum H 2 O contents at 200 ± 10 MPa and 6.3 ± 0.2 wt.% H 2 O for the white pumice melt and 195 ± 15 MPa and 5.2 ± 0.2 wt.% H 2 O for the grey pumice melt. The fluid phase, mainly composed of a H 2 O-rich vapour phase and brine, probably accumulated at the top of the reservoir and generated an overpressure able to trigger the onset of the eruption. Magma degassing was rather homogeneous for the white and grey eruptive units, mostly occurring through closed-system processes, leading to a typical Plinian eruptive style. A steady-state withdrawal of an H 2 O-saturated magma may explain the establishment of a sustained Plinian column. Variation from white to grey pumice is accompanied by decrease of mean vesicularity and increase of mean microcrystallinity and permeability related to significant vesicle coalescence. Despite this, the ascending magma column still evolves under closed-system degassing, without significant gas loss through conduit walls. The Avellino eruption shows numerous similarities with the 79 AD Pompeii eruption in pre-eruptive conditions, degassing processes and eruptive style which are discussed here.

Volcanic activity at Phlegraean Fields, Italy, produced several major marker tephras over a 50 ka period. The caldera forming eruptions of the Campanian Ignimbrite (CI) and Neapolitan Yellow Tuff (NYT) are of particular importance for tephrostratigraphy in Europe. Other key eruptions from this source include the Pomici Principali (PP) and the Tufi Biancastri eruptions. We combine analyses of fresh glasses from proximal locations (i.e., juvenile clasts in proximal flow and fall deposits) with data for key tephra layers from Lago Grande di Monticchio, 120 km to the east. The micron-beam major (EMPA) and trace (LA-ICP-MS) element glass dataset allows us to: (a) distinguish between tephra units produced from the Phlegraean Fields before and during the CI eruption (CI-series), and before and during the NYT and PP eruptions (NYT-series/PP); (b) discriminate between the CI and the geochemically similar Pre-CI pyroclastic deposits; (c) separate the NYT from Pre-NYT tephra units, although both major and trace elements do show significant overlap. The complex compositional overlap between Pre-NYT tephras may present a problem for tephra correlations in the 14–39 ka time window and may have resulted in incorrect proximal–distal and distal–distal correlations. The diagnostic chemical criteria detailed herein permits more accurate matching of distal tephras with their proximal equivalents and hence will improve chronostratigraphy of distal settings and give insight into tephra dispersal. We show that the dispersal of PP tephra was more limited than previously thought. The surge/fall (Lower Member) and subsequent pyroclastic density current (Upper Member) phases of the NYT eruption can be recognised in distal settings. Both the NYT Lower and Upper Members are found in distal localities to the east of the Phlegraean Fields, however the Lower Member is found in the absence of the Upper Member in locations to the far north of Phlegraean Fields. Chemical compositions of the Plinian and ignimbrite phases of the CI eruption overlap extensively, but can be distinguished on a plot of Zr–Th.

Ischia, a volcanic island located 18 miles SW of Naples (Southern Italy), is a densely populated active caldera that last erupted in AD 1302. Melt inclusions in phenocrysts of the Vateliero and Cava Nocelle shoshonite-latite eruptive products (6th to 4th centuries BC) constrain the structure and nature of the Ischia deep magmatic feeding system. Their geochemical characteristics make Ischia a natural borehole for probing the physico-chemical conditions of magma generation in mantle contaminated by slab-derived fluids or melts, largely dominated by CO2. Volatile concentrations in olivine-hosted melt inclusions require gas-melt equilibria at between 3 and 18 km depth. In agreement with what has already been demonstrated at the other neighboring Neapolitan volcanoes (Procida, Campi Flegrei caldera and Somma-Vesuvius volcanic complex), a major crystallization depth at 8-10 km has been identified.The analyzed melt inclusions provide clear evidence for CO2-dominated gas fluxing and consequent dehydration of magma batches stagnating at crustal discontinuities. Gas fluxing is further supported by selective enrichment in K owing to fluid-transfer during magma differentiation.This takes place under oxidized conditions (Fe3+/EFe>=0·3) that can be fixed by an equimolar proportion of divalent and trivalent iron in the melt if post-entrapment crystallization of the host olivine is discarded. The melt inclusion data, together with data from the literature for other Neapolitan volcanoes, show that magmatism and volcanism in the Neapolitan area, despite differences in composition and eruption dynamics, are closely linked to supercritical CO2-rich fluids.These fluids are produced by devolatilization of subducting terrigenous-pelagic metasediments and infiltrate the overlying mantle wedge, generate magmas and control their ascent up to eruption. Geochemical characteristics of Ischia and the other Neapolitan volcanoes reveal that the extent of fluid or melt contamination of the pre-subduction asthenospheric mantle wedge was similar among these volcanoes. However, differences in the isotopic compositions of the erupted magmas (more enriched in radiogenic Sr at Ischia, Campi Flegrei and Somma-Vesuvius with respect to Procida) and the amount of H2O in the plumbing system of these volcanoes (almost double at Ischia, Campi Flegrei and Somma-Vesuvius than at Procida) reflect the different flow-rates of deep slab-derived fluids or melts through the mantle wedge, which, in turn, control the amount of generated magma.The high bulk permeability of the lithosphere below Ischia, Campi Flegrei and Somma-Vesuvius, determined by the occurrence of intersecting NW-SE and NE-SW regional fault systems, favours fluid ascent and accumulation at crustal levels, with consequent larger magma production and storage than at Procida, located along the NE-SW system.

The Averno 2 eruption (3,700 ± 50 a B.P.) was an explosive low-magnitude event characterized by magmatic and phreatomagmatic explosions, generating mainly fall and surge beds, respectively. It occurred in the Western sector of the Campi Flegrei caldera (Campanian Region, South Italy) at the intersection of two active fault systems, oriented NE and NW. The morphologically complex crater area, largely filled by the Averno lake, resulted from vent activation and migration along the NE-trending fault system. The eruption generated a complex sequence of pyroclastic deposits, including pumice fall deposits in the lower portion, and prevailing surge beds in the intermediate-upper portion. The pyroclastic sequence has been studied through stratigraphical, morphostructural and petrological investigations, and subdivided into three members named A through C. Member A was emplaced during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of 10 km. During this phase the eruption reached its climax with a mass discharge rate of 3.2 106 kg/s. Intense fracturing and fault activation favored entry of a significant amount of water into the system, which produced explosions driven by variably efficient water-magma interaction. These explosions generated wet to dry surge deposits that emplaced Member B and C, respectively. Isopachs and isopleths maps, as well as areal distribution of ballistic fragments and facies variation of surge deposits allow definition of four vents that opened along a NE oriented, 2 km long fissure. The total volume of magma extruded during the eruption has been estimated at about 0.07 km3 (DRE). The erupted products range in composition from initial, weakly peralkaline alkali-trachyte, to last-emplaced alkali-trachyte. Isotopic data and modeling suggest that mixing occurred during the Averno 2 eruption between a more evolved, less radiogenic stored magma, and a less evolved, more radiogenic magma that entered the shallow reservoir to trigger the eruption. The early phases of the eruption, during which the vent migrated from SW to the center of the present lake, were fed by the more evolved, uppermost magma, while the following phases extruded the less evolved, lowermost magma. Integration of the geological and petrological results suggests that the Averno 2 complex eruption was fed from a dyke-shaped shallow reservoir intruded into the NE-SW fault system bordering to the west the La Starza resurgent block, within the caldera floor.

The Campi Flegrei caldera collapsed 39 ka in the Neapolitan area (southern Italy) after the Campanian Ignimbrite eruption. This eruption, recognized as the largest and the most cataclysmic volcanic event in the Mediterranean area over the past 200 ka, extruded not less than 300 km3 of trachytic magma. Controversy exists over the timescales required to assemble such large volume of silicic melt and thus whether large magmatic reservoirs can actually persist below active volcanic systems over prolonged periods of time. Uranium-series analyses have been performed on Campanian Ignimbrite whole-rocks, glass matrixes and separated minerals, and the obtained results have been interpreted in combination with data on Sr, Nd, and Pb isotopes from literature. The compositionally most evolved sample which is most radiogenic with respect to Sr isotopes records a reference age of 71 ka. By contrast, U–Th internal isochrones of the three compositionally least evolved samples give identical initial Th isotope ratios and yield consistent ages predating the eruption by up to 6.4 ka. The highest Pb and Nd isotopic ratios and 230Th/232Th activity ratios together with the oldest reference age of the most evolved samples suggest the existence of a resident magma body possibly related to a magmatic system that is known to have fed earlier magmatic activity in the Campi Flegrei area. Conversely, the younger age of the least evolved and least radiogenic magma dates the crystallization/differentiation event of a chemically and isotopically new magma batch entering the reservoir of the resident magma some few thousand years before the cataclysmic eruption. Therefore, the time preceding this large caldera-forming eruption during which the large volume of Campanian Ignimbrite magma assembled and mixed is 6.4 ± 2.1 ka.

The Angolan Mesozoic volcanic suites are concentrated along the continental margin and are characterized by voluminous sheet-like acid rock-types overlying stratoid tholeiitic basalts. The acid volcanics closely correspond in terms of stratigraphy, petrology and Sr-Nd isotope compositions to those of Lower Cretaceous age (135±3 Ma) in the northern Parana basin (SE-Brazil). The Mesozoic tholeiitic volcanic suites of Angola (and Namibia), which crop out close to the continental margin represent the easterly extension of the vast volcanic activity of the Parana basin which occurred before the opening of the S. Atlantic ocean

After the 6 month-long effusive event of 2002-2003, a new lava effusion occurred at Stromboli between 27 February and 2 April 2007. Despite the different durations, approximately the same volume of magma was emitted in both eruptions, in the order of 107 m3. A paroxysmal eruption occurred at the summit craters in both the 2002–2003 and 2007 episodes, during which a significant amount of low porphyritic (LP), volatile-rich magma was erupted. In both cases, the paroxysm did not interrupt the lava emission. Here, we present compositional data, including texture, mineralogy, chemistry and Sr and Nd isotope ratios of bulk-rock, groundmass and separated minerals of lavas erupted in 2007, together with chemistry and Sr and Nd isotope composition of the pumices emitted during the 15 March paroxysm. As a whole, the lavas have the same texture and chemistry that characterize the highly porphyritic (HP) products usually erupted at Stromboli during normal Strombolian activity and effusive events. Compared to the previous HP products, the 2007 lavas show minor but systematic mineralogical and isotopic variations which are consistent with a modest increase of the magma supply rate of the volcano. Compositional variations during the entire duration of the event are very modest. Glass chemistry changes in lavas erupted in the second half of March can be explained by the minor mixing between the volatile-rich LP magma rising through the shallow magmatic system during the 15 March paroxysm and the degassed residing HP magma. A first conclusion of this study is that there is no compositional evidence supporting major changes in the magma dynamics of the volcano accompanying the effusive activity, as also suggested for the 2002–2003 event. The activity of Stromboli is controlled by a steady state feeding system in which refilling, mixing, degassing and crystallization at shallow level continuously operate, with modest oscillations in the magma supply rate. Switching between normal Strombolian and effusive activity is related to periods of relatively more vigorous refilling of the shallow system, leading to progressive pressure increase in the upper conduits associated with only minor compositional variations in the erupted products.

New Sr and Nd isotope data for whole rocks, glasses and minerals are combined to reconstruct the nature and origin of mixing end-members of the 200 km3 trachytic to phonolitic Campanian Ignimbrite (Campi Flegrei, Italy) magmatic system. The least-evolved magmatic end-member shows equilibrium between host glass and the majority of the phenocrysts and is less radiogenic in Sr and Nd than the most-evolved magma. On the contrary, only the Fe-rich pyroxene from the most-evolved erupted magma is in equilibrium with the matrix glass, while all other minerals are in isotopic disequilibrium. These magmas mixed prior to and during the Campanian Ignimbrite eruption and minerals were freely exchanged between the magma batches. Combining the results of the geochemical investigations on magma end-members with geophysical and geological data, we develop the following scenario. In stage 1, a parental, less differentiated magma rose into the middle crust, and evolved through combined crustal assimilation and crystal fractionation. In stage 2, the differentiated magma rose to shallower depth, fed the pre-Campanian Ignimbrite activity and evolved by further open-system processes into the most-evolved and most-radiogenic Campanian Ignimbrite end-member magma. In stage 3, new trachytic magma, isotopically distinct from the pre-Campanian Ignimbrite magmas, rose from ca. 6 km to shallower depth, recharged the most-evolved pre-Campanian Ignimbrite magma chamber, and formed the large and stratified Campanian Ignimbrite magmatic system. During the course of the Campanian Ignimbrite eruption, the two layers were tapped separately and/or simultaneously, and gave rise to the range of chemical and isotopic values displayed by the Campanian Ignimbrite pumices, glasses and minerals.

The northern part of Yemen during the last 30 Ma has been the site of an intense magmatic activity which can be divided into three main episodes. The first episode lasted from 30 to 18 Ma and was characterized by two climaxes. Huge flood basalt eruptions between 30 to 26 Ma were succeeded by massive ignimbrite sheet deposits and intrusion of silicic subvolcanic masses 22 to 20 Ma ago. Contemporaneously, along the present-day western margin of the Yemen Plateau a basaltic dike swarm was emplaced. Additionally, alkaline and peralkaline granites were intruded at the end of the first climax and throughout the second. After a long quiescence, magmatic activity occurred again in Late Miocene time (about 10 Ma) with extrusion of lava flows in scattered areas (e.g. Al Harf, Wadi As Sirr, Maswar Al Hada, Jabal An Nar). The third magmatic episode has been concentrated in three well defined areas. It began about 6.5 Ma ago in the Dhamar Rada area and later in the San'a Amram and Sirwah Marib areas. New chemical and isotopic data on the magmatic products of North Yemen indicate that extensive crustal contamination, together with simple crystal fractionation processes, have been operating during the magmatic evolution. The most primitive products of each of the three episodes share isotopic and petrological features suggesting a similar mantle source. Isotope geochemistry indicates an important asthenospheric component in the mantle source for the magmas of all three episodes. Finally, a comparison between the coeval igneous rocks of the Yemen and Ethiopia plateaus is attempted.

[1] Melt inclusions in phenocrysts of the Minopoli2 shoshonite and Fondo Riccio latite eruptive products (Campi Flegrei caldera; 10.2 to 9.5 ka BP) constrain the nature of deep Phlegraean magmatic fluids, their role in volcanism and give new insights into the magmatic plumbing system. The analyzed melt inclusions show that CO2 is an abundant gaseous species, confirming the results of geochemical studies on the magmatic gas fraction involved in present-day fumarolic emissions. Volatile concentrations within the melt inclusions require gas-melt equilibria between 8 and 9 km depth, and closed-system degassing in presence of ascending CO2-rich fluids of deep provenance. Magmas later re-equilibrate at depths up to 3–2 km, i.e. above the top of the carbonate basement. These observations correlate well with independent geophysical and geochemical evidence and are useful constraints for volcanic hazards assessment at Campi Flegrei.