Abstract
The sulfur compounds released by volcanic eruptions, generally believed to be in the form of SO2 and H2S, may cause global cooling of the atmosphere. However, several recent field and experimental studies suggested that under moderately oxidized conditions hexavalent sulfur species may coexist with SO2 in magmatic fluids and may later be directly emitted at volcanic vents, which contradicts some thermodynamic predictions. We have investigated sulfur speciation in magmatic-hydrothermal fluids by loading different amounts of dilute sulfuric acid into a hydrothermal diamond-anvil cell and performing in situ Raman spectroscopy at temperatures up to 700 °C. Upon heating SO2-4 disappeared beyond 100 °C, and SO2 formed at >250 °C probably due to reduction by the rhenium or iridium gasket. With high-fluid densities (such as >0.9 g/mL), the initial acid and air bubble homogenized into the liquid phase and most sulfur was present in the form of either HSO-4 or H2SO4 (the rest being SO2) within investigated T-P conditions (with pressures up to 10 kb). With low-fluid densities (such as <0.2 g/mL), the system homogenized into the vapor phase and molecular H2SO4 appeared to dominate (with pressures less than 1 kb). These observations strongly suggest that hexavalent sulfur is stabilized by hydration in magmatic fluids.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Actinides in Geology, Energy, and the Environment. Petrography and geochronology of the Pele Mountain quartz-pebble conglomerate uranium deposit, Elliot Lake District, Canada
- Celadonite in continental flood basalts of the Columbia River Basalt Group
- Thermodynamics of manganese oxides: Effects of particle size and hydration on oxidation-reduction equilibria among hausmannite, bixbyite, and pyrolusite
- Grossular: A crystal-chemical, calorimetric, and thermodynamic study
- Redetermination of high-temperature heat capacity of Mg2SiO4 ringwoodite: Measurement and lattice vibrational model calculation
- Thermal behavior of realgar As4S4, and of arsenolite As2O3 and non-stoichiometric As8S8+x crystals produced from As4S4 melt recrystallization
- Thermodynamics of the magnetite-ulvöspinel (Fe3O4-Fe2TiO4) solid solution
- Raman spectroscopy of (Ca,Mg)MgSi2O6 clinopyroxenes
- In-situ Raman spectroscopic study of sulfur speciation in oxidized magmatic-hydrothermal fluids
- Structural anisotropy and annealing-induced nanoscale atomic rearrangements in metamict titanite
- Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: Implication from IR spectra and microtextural observations
- Metastable equilibrium in the C-H-O system: Graphite deposition in crustal fluids
- Controlled morphogenesis of amorphous silica and its relevance to biosilicification
- Structural relaxation in tetrahedrally coordinated Co2+ along the gahnite-Co-aluminate spinel solid solution
- Limitations of Fe2+ and Mn2+ site occupancy in tourmaline: Evidence from Fe2+- and Mn2+-rich tourmaline
- Isothermal compression of face-centered cubic iron
- Bonding and structural changes in siderite at high pressure
- Energetics and kinetics of carbonate orientational ordering in vaterite calcium carbonate
- Growth process and crystallographic properties of ammonia-induced vaterite
- Argesite, (NH4)7Bi3Cl16, a new mineral from La Fossa Crater, Vulcano, Aeolian Islands, Italy: A first example of the [Bi2Cl10]4− anion
- Experimental study of mineral equilibria in the system K2O(Li2O)-Al2O3-SiO2-H2O-HF at 300 to 600 °C and 100 MPa with application to natural greisen systems
- Tobelite and NH+4-rich muscovite single crystals from Ordovician Armorican sandstones (Brittany, France): Structure and crystal chemistry
- The enigmatic iron oxyhydroxysulfate nanomineral schwertmannite: Morphology, structure, and composition
- Ferric iron and water incorporation in wadsleyite under hydrous and oxidizing conditions: A XANES, Mössbauer, and SIMS study
- Kircherite, a new mineral of the cancrinite-sodalite group with a 36-layer stacking sequence: Occurrence and crystal structure
- Molecular models of birnessite and related hydrated layered minerals
- Letter: Gold-telluride nanoparticles revealed in arsenic-free pyrite
- Letter: XAS evidence for the stability of polytellurides in hydrothermal fluids up to 599 °C, 800 bar