Effects of aqueous cations on the dissolution of labradorite feldspar

Journal Article · Thu Oct 31 23:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90482-K· OSTI ID:5201194

Muir, I J; Nesbitt, H W ^[1]

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1. Univ. of Western Ontario, London (Canada)

Specimens of labradorite feldspar (An {approx} 54) were dissolved in mildly acidic solutions containing the cations Al, Ca, and Mg at 9.3 {times} 10{sup {minus}3}, 1.9 {times} 10{sup {minus}2}, and 3.7 {times} 10{sup {minus}2} mmol {center dot} L{sup {minus}1} for 72 days at 21 {plus minus} 2C and atmospheric pressure. Depth profiles by secondary ion mass spectrometry (SIMS) show that the extent to which altered layers form on dissolving labradorite can be influenced by the cation concentration of the leachant solutions. Silicon-enriched altered layers {approx} 1,500 {angstrom} thick form on labradorite surfaces ((001) cleavage faces) during dissolution in aqueous HCl (pH 4). Addition of dissolved Al, Ca, and Mg to the leachant solution reduces the thickness of the altered layers. The formation of thinner altered layers may result from competition between cations and H ions for active surface sites such that the supply of H ions to the labradorite surface is reduced. Dissolved Al in the leachant solutions also alters the release rates of Ca and Al relative to one another. On the other hand, the same is not observed for labradorite specimens dissolved in solutions containing Ca{sub (aq)}. The results from these experiments also support a diffusion-limited processes for the release of Al from fresh labradorite to solutions containing Al{sub (aq)}. Previous attention has been focused on the effects of organic ligands; however, the results demonstrate the important role dissolved cations play in the dissolution of aluminosilicates.

• OSTI ID: 5201194
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:11; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALUMINIUM IONS
CHARGED PARTICLES
CRYSTAL STRUCTURE
DISSOLUTION
FELDSPARS
ION EXCHANGE
IONS
MINERALS
PH VALUE
SILICATE MINERALS
STRUCTURAL CHEMICAL ANALYSIS
SURFACE PROPERTIES
THERMODYNAMIC ACTIVITY
WEATHERING