1,721,044 research outputs found
Petrology of lavas from the 2004–2005 flank eruptionof Mt. Etna, Italy: inferences on the dynamics of magmain the shallow plumbing system
No full textFollowing 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
The isotope geochemistry and volcanology. The Neapolitan volcanoes.
No full textIn recent years isotope geochemistry has contributed more and more to the understanding of the processes of magma genesis and differentiation and to the definition of magmatic systems structure. The application of this discipline to the study of the Neapolitan volcanoes (Vesuvius, Campi Flegrei, Ischia and Procida), since the pioneering work of Hurley et al. (1966), has improved the knowledge of the magmatic systems history and structure, both of which are of great importance for the definition of volcanic hazards and for risk mitigation in the Neapolitan area, where 4 million people live on the slopes of active volcanoes and inside a caldera, that has showed signs of significant unrest in the last 40 years
Evolution and present state of magmatic feeding systems: their significance for volcanic hazard evaluation. Examples from Somma-Vesuvius and Campi Flegrei caldera
No full text
Mineral-Melt Equilibria and Geothermobarometry of Campi Flegrei Magmas: Inferences for Magma Storage Conditions
Full text linkThe eruptions of Campi Flegrei (Southern Italy), one of the most studied and dangerous active volcanic areas of the world, are fed by mildly potassic alkaline magmas, from shoshonite to trachyte and phonotrachyte. Petrological investigations carried out in past decades on Campi Flegrei rocks provide crucial information for understanding differentiation processes in its magmatic system. However, the compositional features of rocks are a palimpsest of many processes acting over timescales of 100–104 years, including crystal entrapment from multiple reservoirs with different magmatic histories. In this work, olivine, clinopyroxene and feldspar crystals from volcanic rocks related to the entire period of Campi Flegrei’s volcanic activity are checked for equilibrium with combined and possibly more rigorous tests than those commonly used in previous works (e.g., Fe–Mg exchange between either olivine or clinopyroxene and melt), with the aim of obtaining more robust geothermobarometric estimations for the magmas these products represent. We applied several combinations of equilibrium tests and geothermometric and geobarometric methods to a suite of rocks and related minerals spanning the period from ~59 ka to 1538 A.D. and compared the obtained results with the inferred magma storage conditions estimated in previous works through different methods. This mineral-chemistry investigation suggests that two prevalent sets of T–P (temperature–pressure) conditions, here referred to as “magmatic environments”, characterized the magma storage over the entire period of Campi Flegrei activity investigated here. These magmatic environments are ascribable to either mafic or differentiated magmas, stationing in deep and shallow reservoirs, respectively, which interacted frequently, mostly during the last 12 ka of activity. In fact, open-system magmatic processes (mixing/mingling, crustal contamination, CO2 flushing) hypothesized to have occurred before several Campi Flegrei eruptions could have removed earlier-grown crystals from their equilibrium melts. Moreover, our new results indicate that, in the case of complex systems such as Campi Flegrei’s, in which different pre-eruptive processes can modify the equilibrium composition of the crystals, one single geothermobarometric method offers little chance to constrain the magma storage conditions. Conversely, combined methods yield more robust results in agreement with estimates obtained in previous independent studies based on both petrological and geophysical methods
The thermal regime of the Campi Flegrei magmatic system reconstructed through 3D numerical simulations
No full textWe 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)
Components and processes in the magma genesis of the Phlegraean Volcanic District and Somma-Vesuvius volcano
No full textGEOITALIA 2007, 6° Forum Italiano di Scienze della Terra, F.I.S.T., Rimini, 12-14 September 200
A two-component mantle below Mt Etna volcano: evidences from noble gas and trace element geochemistry of primitive products
No full textA general geochemical study comprehensive of major elements, trace elements and Sr-Nd isotopes in the bulk rock, coupled to noble gases analyses from fluid inclusions retained in minerals, was performed. The studied samples ( basalts, trachybasalts and basanites) represent some among the most primitive products of Etnean history. The variable composition measured in trace elements (i.e. Zr/Nb=2.81–4.98, Ce/Yb=35.02–66.90, La/Yb=15.36–35.52, Th/Y=0.17–0.43) was modeled as due to varying degrees of melting of a common mantle source. We numerically simulated the process by MELTS code to calculate a melting percentage for each product, and we accordingly estimated the pristine trace-elements content of their mantle source. This latter resulted to be common to all of the investigated samples and evidenced a close affinity between Etnean and Hyblean mantle. The observed coupling between trace elements and noble gases allow us to better define the Etnean mantle, which is compatible with a peridotitic matrix veined by 10% of clinopyroxenites. The geochemistry of the Sr-Nd-He isotopes (87Sr/86Sr= 0.703321–0.703910, 143Nd/144Nd= 0.512836 – 0.512913 and 3He/4He= 6.7–7.6 Ra), evidence also that crustal-derived fluids contaminated at various degrees the inferred source (?) The 87Sr/86Sr enrichment appears correlated to estimated degree of melting for each product, therefore the metasomatic fluids probably refertilized some portions of the mantle prior to partial melting. In contrast, the observed decoupling between 3He/4He and 87Sr/86Sr ratios could be related to shallower processes, due to magma aging or to a contribution of shallow fluids, responsible of the more radiogenic values of 3He/4He
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