Complexity of mineral dissolution as viewed by high resolution scanning auger microscopy: labradorite under hydrothermal conditions
The dissolution of labradorite under hydrothermal conditions has been studied by exposing a packed core of fine-grained labradorite powder to deionized water at 300/sup 0/C and 300 bars for 57 days using a single-pass flow-through apparatus. The principal methods used for characterizing the labradorite dissolution were high lateral resolution scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), and measurement of the exit solution chemistry. Under these hydrothermal conditions, boehmite and halloysite precipitate throughout the core and the labradorite powder undergoes extensive dissolution. The reacted labradorite surfaces are incongruently modified to levels as deep as 20 A (for Al and Si) to 30 A (for Na and Ca), although the distribution of elements within this depth or deeper is not yet know. The modified surface chemistry not only changes systematically down the length of the core, but is also locally variable. The dissolution mechanism of labradorite under hydrothermal conditions as revealed by SAM is highly complex, and the variability in surface chemistry is probably controlled by the local density and distribution of microcracks and crystal defects, the starting morphology of each labradorite surface, and the local flow patterns of reacting solution over that surface. Our results are contrary to previous XPS studies of dissolving feldspars (at or near room temperature) which do not report dramatic changes in near-surface chemistries. Part of the difference between the XPS and Auger results may be due to the difference in the depth of analysis associated with the characteristic electrons utilized by the two techniques.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 5100368
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 52:2; ISSN GCACA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
150201 -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)
58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
AUGER ELECTRON SPECTROSCOPY
CHEMICAL REACTION KINETICS
DISSOLUTION
ELECTRON SPECTROSCOPY
ENERGY SYSTEMS
FELDSPARS
FLUIDS
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
HYDROTHERMAL ALTERATION
HYDROTHERMAL SYSTEMS
KINETICS
MINERALS
REACTION KINETICS
ROCK-FLUID INTERACTIONS
SOLUBILITY
SPECTROSCOPY
TEMPERATURE EFFECTS