Abstract
The Raman spectra of fluids in equilibrium with solid quartz in the system H2O-SiO2 were measured to 900 °C and 14 kbar using an externally heated diamond cell. Dissolved silica species were identified by comparing the measured spectra with calculated normal mode frequencies and Raman intensities. At crustal pressures and temperatures, H4SiO4 is the dominant silica species in aqueous fluids, with a strong Raman band at 760-785 cm-1. At the P-T conditions of the upper mantle, however, H6Si2O7 dimers and possibly higher polymers coexist with H4SiO4 in the fluid. The most intense Raman bands of H6Si2O7 occur at about 630, 920, and 230 cm-1. The presence of high concentrations of ionized silica species in the solution can be ruled out. The observed speciation changes explain the drastic increase of silica solubility in water at lower crustal and upper mantle PT conditions.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
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Articles in the same Issue
- Iron concentration and the physical processes of dynamic oxidation in an alkaline earth aluminosilicate glass
- A crystal chemical re-evaluation of amphibole/melt and amphibole/clinopyroxene DTi values in petrogenetic studies
- Mineralogy of mafic xenoliths and their reaction zones in the olivine lamproite from Prairie Creek Arkansas and the paragenesis of haggertyite, Ba [Fe6Ti5Mg]O19
- Magmatic anhydrite in granitic rocks: First occurrence and potential petrologic consequences
- Crystal chemistry of Al-rich biotites coexisting with muscovites in peraluminous granites
- Spectroscopic and structural properties of synthetic micas on the annite-siderophyllite binary: Synthesis, crystal structure refinement, Mössbauer, and infrared spectroscopy
- Thermodynamic properties of tremolite: A correction and some comments
- Raman spectroscopic characteristics of Mg-Fe-Ca pyroxenes
- Hydrogen in diopside: Diffusion profiles
- Diffusion of C and O in calcite at 100 MPa
- Solubility and stability of zeolites in aqueous solution: II. Calcic clinoptilolite and mordenite
- TEM and SFM of exsolution and twinning in an alkali feldspar
- Equation of state of magnetite and its high-pressure modification: Thermodynamics of the Fe-O system at high pressure
- Optimization of site occupancies in minerals using quadratic programming
- Leverage analysis and structure refinement of minerals
- The absolute energy positions of conduction and valence bands of selected semiconducting minerals
- Antiferroelectric phase transition in titanite: Excess entropy and short range order
- P4/n and P4nc long-range ordering in low-temperature vesuvianites
- Tetrahedral vacancies and cation ordering in low-temperature Mn-bearing vesuvianites: Indication of a hydrogarnet-like substitution
- Sodic-ferripedrizite, a new monoclinic amphibole bridging the magnesium-iron-manganese-lithium and the sodium-calcium groups
- The crystal structure of peprossiite-(Ce), an anhydrous REE and Al mica-like borate with square-pyramidal coordination for Al
- Crystal chemistry of the new mineral brandholzite, Mg(H2O)6[Sb(OH)6]2, and of the synthetic analogues M2+(H2O)6[Sb(OH)6]2 (M2+ = Mg, Co)
- Letters. In-situ Raman spectra of dissolved silica species in aqueous fluids to 900 °C and 14 kbar
- Quetzalcoatlite: A new octahedral-tetrahedral structure from a 2 × 2 × 40 μm3 crystal at the Advanced Photon Source-GSE-CARS Facility
- Bonding and dynamics of Mg in pyrope: a theoretical investigation
- Structure of a new Al-rich phase, [K, Na]0.9[Mg, Fe]2[Mg, Fe, Al, Si]6O12, synthesized at 24 GPa
- Core level electron binding energies of realgar (As4S4)
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