Experimental approach to constrain second critical end points in fluid/silicate systems: Near-solidus fluids and melts in the system albite-H2O
-
Roland Stalder
,
Peter Ulmer
Abstract
Experimental investigations in the system albite-water have been carried out to evaluate the accuracy of a new procedure to determine major-element solubilities in fluid phases and water solubilities in melts. The system albite-water had been examined previously and some consensus has been achieved with respect to phase relations, solidi, and water solubilities in the melts. Above 15 kbar the system approaches a second critical end point, where a distinction between fluid and melt no longer can be made and the term solidus has to be reconsidered.
All experimental runs were carried out at near-solidus conditions at 5-17 kbar and 625-775 °C. Experimental charges contained albite, water, and a layer of diamond crystals (grain size 50 mm). The pore space between the diamonds is preserved during the run indicating that the fluid was able to circulate throughout the entire capsule. During quenching, the material dissolved in the fluid precipitated between the diamond crystals and, as a result, could so be separated from the solid residue. The recovered capsules were directly embedded in epoxy and the diamond layers were analysed by laser ablation microprobe (LAM-ICP-MS).
The new method allows the determination of a broad range of silicate/water ratios in aqueous fluids and hydrous melts. In some experimental runs at 15 and 17 kbar, fluids with approximately 40 wt% solute could be trapped leading to the conclusion that supercritical conditions were reached.
Results furthermore indicate that albite dissolves non-stoichiometrically at 5 kbar producing a higher Na/Al and Si/Al in the solute than in the melt. Dissolution and melting at 10 kbar and higher pressures appears to be congruent within the limits of this method.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Eclogite-facies relics and inferred ultrahigh-pressure metamorphism in the North Dabie Complex, central-eastern China
- Application of INVEQ to the geothermobarometry of metamorphic rocks near a kyanite-sillimanite isograd, Mica Creek, British Columbia
- Microstructural characterization of metamorphic magnetite crystals with implications for oxygen isotope distribution
- Coexisting monazite and allanite in peraluminous granitoids of the TribečMountains, Western Carpathians
- Effect of alkalis, phosphorus, and water on the surface tension of haplogranite melt
- Direct observation of immiscibility in pyrope-almandine-grossular garnet
- On the cluster analysis of grains and crystals in rocks
- Experimental approach to constrain second critical end points in fluid/silicate systems: Near-solidus fluids and melts in the system albite-H2O
- Estimation and testing of standard molar thermodynamic properties of tourmaline end-members using data of natural samples
- An investigation of matrix effects in the analysis of fluorine in humite-group minerals by EMPA, SIMS, and SREF
- New data on the crystal-chemistry of fluoborite by means of SREF, SIMS, and EMP analysis
- Effect of aluminum on Ti-coordination in silicate glasses: A XANES study
- XAFS study of Cu model compounds and Cu2+ sorption products on amorphous SiO2, γ-Al2O3, and anatase
- Oxidation-reduction mechanism of iron in dioctahedral smectites: I. Crystal chemistry of oxidized reference nontronites
- Oxidation-reduction mechanism of iron in dioctahedral smectites: II. Crystal chemistry of reduced Garfield nontronite
- 15N NMR study of nitrate ion structure and dynamics in hydrotalcite-like compounds
- 29Si and 27Al MAS-NMR spectroscopy of b-eucryptite (LiAlSiO4): The enthalpy of Si,Al ordering
- The nuclear and magnetic structure of “white rust”—Fe(OH0.86D0.14)2
- In-situ study of the R3̅ to R3̅c phase transition in the ilmenite-hematite solid solution using time-of-flight neutron powder diffraction
- In situ X-ray diffraction investigation of lawsonite and zoisite at high pressures and temperatures
- A shell model for the simulation of rhombohedral carbonate minerals and their point defects
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- The crystal structure of gearksutite, CaAlF4(OH)· H2O
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- Kinoshitalite, Ba(Mg)3(Al2Si2)O10(OH,F)2, a brittle mica from a manganese deposit in Oman: Paragenesis and crystal chemistry
- The crystal structure of parisite-(Ce), Ce2CaF2(CO3)3
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