Experimental investigation of talc solubility in H sub 2 O-MgCl sub 2 -NaCl-HCl fluids in the range 500-700C, 2 kb
- Texas A and M Univ., College Station (United States)
The equilibrium solubility of the talc-quartz mineral assemblage in H{sub 2}O-MgCl{sub 2}-NaCl-HCl fluids at 2 kb and temperatures in the range 500-700C has been determined using rapid-quench hydrothermal techniques. At 500C, the concentration of Mg measured in the fluid after quench decreased in a systematic, nonlinear fashion with increasing concentrations of NaCl, from 2.8 m Mg in NaCl-free solutions to 1.5 m in 5.1 m NaCl. In contrast, at 600 and 700C Mg molalities increased with increasing NaCl molalities. At 600C, the concentration of Mg increased from 0.072 to 0.12 m as the concentration of NaCl increased from 0.0 to 6.1 m. At 700C, Mg molality increased from an NaCl-free value of 0.0078 m, to 0.031 m in 6.3 m NaCl. The observed solubilities were compared to concentrations of aqueous species calculated by solving the series of mass-action and mass-balance equations that describe the activities and molalities of the relevant species in the fluid. It is concluded that at 500C, MgCl{sub 2}{sup 0}, MgCl+, and Mg{sup 2+} are the only Mg-species necessary to account for the observed behavior. The calculations suggest that the decrease in Mg results from both the increasing concentrations of Cl{sup {minus}} as NaCl concentration increases, and the changing dielectric properties of the fluid. At 600 and 700C, the presence of Mg-species in addition to MgCl{sub 2}{sup 0}, MgCl{sup +}, and Mg{sup 2+} may be required to describe the increased solubility observed in the experiments. Use of the slope-quantification method for identifying aqueous species indicates that higher order Mg-Cl species or Na-Mg-Cl species are possible, but the precision of the technique is not sufficient to uniquely identify the species.
- OSTI ID:
- 7114344
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:10; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHELATING AGENTS
CHLORIDES
CHLORINE COMPOUNDS
COMPLEXES
EQUILIBRIUM
HALIDES
HALOGEN COMPOUNDS
HYDROCHLORIC ACID
HYDROGEN COMPOUNDS
INORGANIC ACIDS
MAGNESIUM CHLORIDES
MAGNESIUM COMPOUNDS
METAMORPHISM
MINERALS
OXIDE MINERALS
PRESSURE EFFECTS
QUARTZ
SILICATE MINERALS
SILVER CHLORIDES
SILVER COMPOUNDS
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLUBILITY
SOLVENT PROPERTIES
TALC
TEMPERATURE EFFECTS
THERMODYNAMIC ACTIVITY
TRANSITION ELEMENT COMPOUNDS