0000000000186006
AUTHOR
A Paonita
Geochemical modeling of mixing between magmatic and hydrothermal gases: the case of Vulcano Island, Italy
Abstract In this study we present a geochemical approach to model the mixing of magmatic and hydrothermal gases. Our model is based on a rigorous formulation of a perfectly dimensioned system of mass and energy balance equations. Inputs of the equation set are the H2O and CO2 content and gas emission temperature at the surface, together with some constraints gained from the chemical–physical features of the hydrothermal system. The output data give the composition of magmatic gas, mixing fractions and temperatures of gas mixtures in the mixing zone. The comparison of the emission temperature of fumarolic gases with their calculated mixing temperatures provides valuable indications on the ex…
Investigation of the noble gas solubility in H2O–CO2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model
A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H2O–CO2 gas phase with noble gas as a minor component, in a large range of pressures (at least up to 300 MPa). The model is based on the relationship between the concentration of dissolved noble gas and ionic porosity of the melt, found by Carroll and Stolper [Geochim. Cosmochim. Acta 57 (1993) 5039–5051] for H2O–CO2 free melts. It evaluates the effect of dissolved H2O and CO2 on the melt ionic porosity and, consequently on Henry’s constants of noble gases. The fugacities of the noble gases in the H2O–CO2–noble gas mixtures are also considered in our equilibrium calculations of diss…
Elemental and isotope covariation of noble gases in olivines and pyroxenes from Etnean volcanics erupted during 2001-2005, and genetic relation with peripheral gas discharges. Implication for volcanic surveillance.
Investigation of the He solubility in H2O-CO2 bearing silicate liquids at moderate pressure: a new experimental method
We have designed the first available experimental method capable to investigate the solubility of inert gases in H2O–CO2 bearing silicate melts in a large range of pressures. The method overcomes the difficulties imposed by the physical state of volatiles at room conditions. Experiments were done by using an internally heated pressure vessel, where sealed capsules containing the sample are introduced. The peculiarity of the method consists in the capability of loading, in accurately known proportions (even lower than ppm), volatiles in a gaseous state at room conditions. Gas is loaded as a weighed amount of a gas-bearing glass, which was previously prepared by using the same gas as a pressu…
A two-component mantle below Mt Etna volcano: evidences from noble gas and trace element geochemistry of primitive products
A 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 co…
A two-component mantle extending from Hyblean Plateau to Mt Etna (Eastern Sicily) as inferred by an integrated approach with noble gases, trace elements and isotope geochemistry.
We carried out a geochemical investigation of the mantle beneath Hyblean and Etnean area through ultramafic xenoliths (peridotites and pyroxenites) retained in Miocenic age Hyblean volcanics and primitive Etnean lavas and tephra, respectively. Major and trace elements and Sr-Nd isotopes (whole rock and /or minerals) were analysed together with noble gases entrapped in fluid inclusions hosted in olivines and pyroxenes phenocrysts. The geochemical results from Hyblean xenoliths study highlighted the presence of two distinct compositional groups: the peridotites, featured by a more enriched geochemical fingerprint (3He/4He ∼7 Ra, 143Nd/144Nd ∼0.5129 and Zr/Nb ∼ 4) whereas the pyroxenites, char…