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Barbato, D.
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Barbato, D.
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- PublicationRestrictedHeterogeneous large total CO2 abundance in the shallow magmatic system of Kilauea volcano, Hawaii(2009-12-09)
; ; ; ; ; ; ; ;Barsanti, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Barbato, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Moretti, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia ;Hauri, E.; Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, D. C., USA ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; ; ; ; Due to its very low solubility in silicate melts, CO2 concentrations in melt inclusions (MIs) within crystals are commonly orders of magnitude less than the total concentration in the multiphase magma, strongly limiting the possibility to constrain CO2 abundance based on the dissolved quantities. Here we develop a statistical method to process MI data, which allows analytical uncertainties to be taken into account together with the peculiar features of the local saturation surface. The method developed leads to retrieve total H2O and CO2 concentrations in magma as well as the gas phase abundance at the time of magma crystallization. Application to a set of 29 high-resolution secondary ion mass spectrometry (SIMS) MI data from a single specimen of the 1842–1844 eruption of Kilauea, Hawaii, reveals the existence of heterogeneous total CO2 abundance, and of at least 2–6 wt % total CO2 in some magma batches, two orders of magnitude higher than the dissolved amounts and 30–50 times more abundant than the corresponding total H2O content. Heterogeneous total volatile concentrations are interpreted as due to a combination of degassing and gas flushing in magma subject to convective motion at shallow depth where P < 100 MPa. In such a view, the magma rising to shallow depth in the volcanic system carries initially a total volatile content ≤1 wt %, corresponding to the determined low total CO2 population, and consistent with previous global estimates. The high CO2 populations correspond to progressive CO2 enrichment due to degassing at low P and flushing from a deep CO2-rich gas. A total CO2 content >1 wt % is likely to characterize the >30 km deep magma, not represented in the analyzed inclusions, from which a CO2-rich gas phase exsolves and decouples from the liquid.238 18 - PublicationRestrictedNumerical simulation of the dynamics of fluid oscillations in a gravitationally unstable, compositionally stratified fissure(2008)
; ; ; ; ; ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Barbato, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Barsanti, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; ; We have simulated the dynamics of convection, mixing and ascent of two basaltic magmas differing in their volatile and crystal content, giving rise to a gravitationally unstable configuration along a dyke or fissure. Numerical simulations are performed by a recently developed code which describes the transient 2D dynamics of multicomponent fluids from the incompressible to the compressible regime, and the initial and boundary conditions are inspired to the paroxysmal eruption which occurred at Stromboli in 2003 (D'Auria et al. 2006). Multicomponent (H2O+CO2) saturation is accounted for by modelling the non-ideal equilibrium between the gas phase and the melt. The numerical results show the formation of a rising bulge of light magma, and the sink of discrete batches of dense magma towards deep fissure regions. Such dynamics are associated with a complex evolution of the pressure field, which shows variations occurring over a wide spectrum of frequencies. A first order analysis of the propagation of such pressure disturbances through the country rocks shows that the pre-eruptive fissure dynamics are able to produce mm-size, mainly radial deformation of the volcano, and a detectable seismic signal with spectral peaks at periods of about 50 s.228 24