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Title: The formation of leached layers on albite surfaces during dissolution under hydrothermal conditions

Abstract

Hydrothermally altered (225{degree}C) albite was compositionally depth-profiled using X-ray photoelectron spectroscopy (XPS) coupled with calibrated Ar ion sputtering. Solution data were collected during dissolution runs for the same crystals which were spectroscopically analyzed. We found that leached zones depleted in Na, Al, and O develop during the initial, incongruent phase of dissolution. Angle resolved XPS (ARXPS) demonstrated that Na and Al are significantly depleted from the upper few monolayers. Depths of leaching, which range from 10 to 900 {angstrom}, decrease with increasing pH in the acid region and increase with pH in the basic region. Based on calculated dissolution rates the depth of leaching can be roughly correlated with the release rate of Si. Preliminary evaluations of diffusion transport rates through leached layers suggest that dissolution is not rate limited by diffusion. Instead, the kinetics of dissolution seem to be related to the intrinsic rate of structural hydrolysis. Using the XPS and solution data in conjunction with theoretical and experimental studies in the literature, we propose a dissolution mechanism based on initial ion exchange followed by the hydrolysis of Al and Si, which is modeled as the breakdown of activated complexes formed at bridging oxygen (O{sub br}) sites. Elemental massmore » balances based on comparisons between the XPS and solution data suggest that dissolution occurs non-uniformly and is probably preferentially constrained to dislocations and macroscopic defects within the structure.« less

Authors:
;  [1]; ;  [2]
  1. Princeton Univ., NJ (USA)
  2. Stanford Univ., CA (USA)
Publication Date:
OSTI Identifier:
6014207
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta; (USA)
Additional Journal Information:
Journal Volume: 54:5; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; 58 GEOSCIENCES; ALBITE; DISSOLUTION; HYDROTHERMAL ALTERATION; HYDROTHERMAL SYSTEMS; ROCK-FLUID INTERACTIONS; LEACHING; MASS BALANCE; PH VALUE; REACTION KINETICS; X-RAY SPECTROSCOPY; ENERGY SYSTEMS; FELDSPARS; GEOTHERMAL SYSTEMS; KINETICS; MINERALS; SEPARATION PROCESSES; SILICATE MINERALS; SPECTROSCOPY; 152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions; 580000 - Geosciences

Citation Formats

Hellmann, R, Crerar, D A, Eggleston, C M, and Hochella, Jr, M F. The formation of leached layers on albite surfaces during dissolution under hydrothermal conditions. United States: N. p., 1990. Web. doi:10.1016/0016-7037(90)90152-B.
Hellmann, R, Crerar, D A, Eggleston, C M, & Hochella, Jr, M F. The formation of leached layers on albite surfaces during dissolution under hydrothermal conditions. United States. https://doi.org/10.1016/0016-7037(90)90152-B
Hellmann, R, Crerar, D A, Eggleston, C M, and Hochella, Jr, M F. 1990. "The formation of leached layers on albite surfaces during dissolution under hydrothermal conditions". United States. https://doi.org/10.1016/0016-7037(90)90152-B.
@article{osti_6014207,
title = {The formation of leached layers on albite surfaces during dissolution under hydrothermal conditions},
author = {Hellmann, R and Crerar, D A and Eggleston, C M and Hochella, Jr, M F},
abstractNote = {Hydrothermally altered (225{degree}C) albite was compositionally depth-profiled using X-ray photoelectron spectroscopy (XPS) coupled with calibrated Ar ion sputtering. Solution data were collected during dissolution runs for the same crystals which were spectroscopically analyzed. We found that leached zones depleted in Na, Al, and O develop during the initial, incongruent phase of dissolution. Angle resolved XPS (ARXPS) demonstrated that Na and Al are significantly depleted from the upper few monolayers. Depths of leaching, which range from 10 to 900 {angstrom}, decrease with increasing pH in the acid region and increase with pH in the basic region. Based on calculated dissolution rates the depth of leaching can be roughly correlated with the release rate of Si. Preliminary evaluations of diffusion transport rates through leached layers suggest that dissolution is not rate limited by diffusion. Instead, the kinetics of dissolution seem to be related to the intrinsic rate of structural hydrolysis. Using the XPS and solution data in conjunction with theoretical and experimental studies in the literature, we propose a dissolution mechanism based on initial ion exchange followed by the hydrolysis of Al and Si, which is modeled as the breakdown of activated complexes formed at bridging oxygen (O{sub br}) sites. Elemental mass balances based on comparisons between the XPS and solution data suggest that dissolution occurs non-uniformly and is probably preferentially constrained to dislocations and macroscopic defects within the structure.},
doi = {10.1016/0016-7037(90)90152-B},
url = {https://www.osti.gov/biblio/6014207}, journal = {Geochimica et Cosmochimica Acta; (USA)},
issn = {0016-7037},
number = ,
volume = 54:5,
place = {United States},
year = {Tue May 01 00:00:00 EDT 1990},
month = {Tue May 01 00:00:00 EDT 1990}
}