Search results for "Inclusions"
showing 10 items of 82 documents
Variation of H2O/CO2and CO2/SO2ratios of volcanic gases discharged by continuous degassing of Mount Etna volcano, Italy
2008
[1] We applied the Multi-GAS technique to measure compositions of the volcanic plumes continuously discharged from summit craters of Voragine, Northeast and Bocca Nuova at Mount Etna, in an attempt to estimate compositions of the source volcanic gases. The estimated CO2/SO2 and H2O/CO2 ratios of the volcanic gases show a large variation ranging from 0.6 to 30 and from 1 to 18, respectively. This variability overlaps with the compositional range of dissolved volatiles in melt inclusions and their coexisting bubbles in a magma chamber and can be caused by the low-pressure degassing of a magma with variable bubble content ranging from 0.3 to 15 wt.%. The variable bubble content in the magma is…
Geochemical heterogeneities in magma beneath Mount Etna recorded by 2001-2006 melt inclusions
2015
We present a geochemical study on olivine and clinopyroxene-hosted melt inclusions (MIs) from 2001 to 2006 Etna basaltic lavas and pyroclastites. Three MI suites are distinguished on the basis of trace element fingerprinting. Type-1 MIs (from 2001 Upper South and 2002 Northeast vents) share their trace element signature with low-K lavas erupted before 1971. Critical trace element ratios (e.g., K/La, Ba/Nb), along with Pb isotope data of Type-1 MIs provide evidence for a heterogeneous mantle source resulting from mixing of three end-members with geochemical and isotopic characteristics of EM2, DMM, and HIMU components. Type-1 MIs composition does not support involvement of subduction-related…
Experimental calibration and implications of olivine-melt vanadium oxybarometry for hydrous basaltic arc magmas
2018
The strong dependence of vanadium partitioning between olivine and silicate melt (DVOl-M) on redox conditions (fO2) can be used as sensitive oxybarometer in magmatic systems. Here we extend the experimental database on DVOl-M, obtained so far at high temperatures (mainly above 1250 °C), to lower temperatures that are typical for island-arc basalts. Crystallization experiments were performed using a composition from Mutnovsky volcano (Kamchatka), and the investigated temperature, pressure, and oxygen fugacity ranges were 1025–1150 °C, 0.1 and 0.3 GPa, and ΔQFM of –0.5 to +3.2, respectively. The water content in melts ranged from 0.6 to ∼6.5 wt% H2O. The data demonstrate a strong negative cor…
Crater Gas Emissions and the Magma Feeding System of Stromboli Volcano
2013
Quiescent and explosive magma degassing at Stromboli volcano sustains high-temperature crater gas venting and a permanent volcanic plume which constitute key sources of information on the magma supply and dynamics, the physical processes controlling the explosive activity and, more broadly, the volcano feeding system. The chemical composition and the mass output of these crater emissions (gases, trace metals, radioactive isotopes) were measured using different methodologies: within-plume airborne measurements, ground-based plume filtering, and/or in situ analysis, remote UV and open-path Fourier transform infrared absorption spectroscopy. The results obtained, summarized in this paper, demo…
METAMORPHIC EVOLUTION OF SPESSARTINE QUARTZITES (COTICULES) IN THE HIGH-PRESSURE, LOW-TEMPERATURE COMPLEX AT BAHIA MANSA, COASTAL CORDILLERA OF SOUTH…
2001
Lenses of spessartine quartzites (coticules) are associated with greenschist intercalations in coastal exposures at Bahia Mansa within the mainly metapsammopelitic Western Series, which forms most of the basement in the Coastal Cordillera of central to southern Chile. The chemical compositions of the coticules can be explained by protoliths formed from ferriferous and manganiferous hydrothermal precipitates mixed with aluminous alteration-derived material on top of oceanic crust. The peak conditions of metamorphism were calculated with multivariant reactions: 270–370 °C, 6–8 kbar. A retrograde P–T evolution was marked by decompression to 2 kbar during cooling below 300°C, influx of an exter…
Shrinkage Bubbles: The C–O–H–S Magmatic Fluid System at San Cristóbal Volcano
2018
New analytical results for the composition of shrinkage bubbles (09-70 vol. %) in olivine-hosted (Fo <80%) primary melt inclusions (MIs) have been incorporated into a novel geochemical model for San Cristó bal volcano, Nicaragua. The vapour, liquid, and mineral components found inside shrinkage bubbles may represent relics of early C-O-H-S fluids exsolved from a magmatichydrothermal system. This conclusion is supported by high-resolution Raman microspectroscopy revealing: (1) gaseous CO2 (d=0·17-0·31 g/cm3 in 31 samples) coexisting with liquid H2O (in seven samples) at ambient temperature (<22°C) inside the shrinkage bubbles of naturally quenched inclusions; (2) several mineral phases (i.e.…
HYDROTHERMAL CARBONATES OF THE SCHWARZWALD ORE DISTRICT, SOUTHWESTERN GERMANY: CARBON SOURCE AND CONDITIONS OF FORMATION USING 18O, 13C, 87Sr/86Sr,…
2012
Diagenetic carbonates, metamorphic carbonates, primary hydrothermal carbonates, and secondary remobilized carbonates (including sinters) from the Schwarzwald ore district in SW Germany formed in various tectonic settings and hydrothermal environments over a period of almost 300 Ma. They were investigated in order to define sources of carbon, dispersion of carbon during fluid-rock interaction processes and, where possible, to specify geochemical fingerprints for carbonates formed during different processes and in different geochemical and tectonic environments. For this purpose, 335 samples of calcite, ankerite, dolomite, siderite, and strontianite from 92 localities in 46 mining areas in th…
The role of trapped fluids during the development and deformation of a carbonate/shale intra-wedge tectonic mélange (Mt. Massico, Southern Apennines,…
2020
Abstract Numerous studies exist on exhumed tectonic melanges along subduction channels whereas, in accretionary wedge interiors, deformation mechanisms and related fluid circulation in tectonic melanges are still underexplored. We combine structural and microstructural observations with geochemical (stable and clumped isotopes and isotope composition of noble gases in fluid inclusions of calcite veins) and U-Pb geochronological data to define deformation mechanisms and syn-tectonic fluid circulation within the Mt. Massico intra-wedge tectonic melange, located in the inner part of the central-southern Apennines accretionary wedge, Italy. This melange developed by shear deformation at the bas…
New approach for quantifying water depth applied to the enigma of drowning of carbonate platforms
2002
This research illustrates application of a fluid-inclusion technique for quantifying water depth of ancient carbonate platforms. Jurassic limestones of Monte Kumeta, Italy, were cemented with submarine calcite during a transition to carbonate platform termination. The calcite cements contain fluid inclusions consisting of Jurassic seawater and immiscible gas bubbles trapped during the growth and penecontemporaneous recrystallization of the cements. Crushing analysis indicates that gas bubbles are under pressures indicative of entrapment in water depths of 23–112 m. Assuming simple deepening and acknowledging chronostratigraphic errors, rates of relative rise in sea level were initially less…
Escape of Supercritical-CO2 Fluids Trapped in Calcite Nano-metric Pores
2019
Flow of supercritical CO2-bearing fluids through a rock is a fundamental phenomenon which acts upon a great many geological processes ranging from seismic activity to formation of ore deposits. Atomic Force Microscopy scanning experiments allowed us to infer movement of supercritical CO2-bearing fluids through calcite crystals and relate it to natural decrepitation of nanoscale fluid inclusions. Calculated velocities exceed the rate of diffusion predicated via current vacancy models by several orders of magnitude implying that CO2-rich fluid movement through micro and nano-pore space may presently be greatly underestimated.