Kinetics of quartz precipitation and dissolution under hydrothermal conditions at 100 to 300[degree]C
- Pennsylvania State Univ., University Park, PA (United States). Ore Deposits Research Section
Precipitation and dissolution rates of powdered quartz were measured in pure water (DDW) and aqueous KCl and NaCl solutions at 100 to 300 C and near neutral pH. For precipitation experiments, Si concentrations of the input solutions were carefully controlled to be supersaturated in respect to quartz and undersaturated in respect to amorphous silica. The dependence of the rate of reaction on the Si saturation state of the solution, temperature (T), and the molal electrolyte concentration (m) was evaluated. Experiments show that the rates for quartz dissolution or precipitation are a linear function of the deviation from equilibrium as expressed by the activity ratio Q. The change of k+ as a function of temperature was investigated by precipitation and dissolution experiments in DDW and 0.2, 0.1, 0.02, 0.01, and 0.005 m KCl solutions at 100 to 300 C. The ln k+ values from the DDW experiments and the ln k+ from each of the experiments in KCl solutions are a linear function of 1/T. This indicates that the reaction mechanism is unchanged over this temperature range in each solution. The average activation energy of quartz dissolution in DDW and in KCl solutions is 18.3 [+-] 0.7 kcal/mol. The rate of reaction increases as a function of increasing electrolyte concentration (NaCl or KCl). Data show that log k+ increases linearly with log m. The dependence may be caused by site competition between H[sup +] and the alkali ions to bond with OH[sup [minus]] of H[sub 4]SiO[sub 4] either on the quartz surface or within the absorbed aqueous double layer.
- OSTI ID:
- 5901669
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
152003* -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
ACTIVATION ENERGY
ALKALI METAL COMPOUNDS
CHLORIDES
CHLORINE COMPOUNDS
DISSOLUTION
ENERGY
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
MINERALS
OXIDE MINERALS
OXYGEN COMPOUNDS
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
PRECIPITATION
QUARTZ
RESERVOIR TEMPERATURE
ROCK-FLUID INTERACTIONS
SEPARATION PROCESSES
SODIUM CHLORIDES
SODIUM COMPOUNDS
SOLVENT PROPERTIES
WATER