Effect of oxalate on the dissolution rates of oligoclase and tremolite

Journal Article · Tue Sep 01 00:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90306-1· OSTI ID:5099968

Mast, M A; Drever, J I

The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22/sup 0/C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of release of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si. Large transient spikes of Al or Si are observed when oxalate is added to or removed from the system. The cause of the spikes is unknown; the authors suggest adsorption feldspar surfaces away from sites of active dissolution as a possibility. The rate of dissolution of tremolite is independent of pH over the pH range 2-5, and decreases at higher pH. The rate of dissolution of oligoclase in these experiments was independent of pH over the pH range 4-9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor.

• Research Organization: Univ. of Wyoming, Laramie (USA)
• OSTI ID: 5099968
• Journal Information: Geochim. Cosmochim. Acta; (United States), Vol. 51:9
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
AMPHIBOLE
CHEMICAL REACTION KINETICS
DISSOLUTION
GEOCHEMISTRY
FELDSPARS
ALUMINIUM
BENCH-SCALE EXPERIMENTS
CHELATING AGENTS
CHEMICAL REACTIONS
CHEMICAL REACTORS
EXPERIMENTAL DATA
GRANITES
OXALATES
PH VALUE
SILICON
SOLUBILITY
WEATHERING
CARBOXYLIC ACID SALTS
CHEMISTRY
DATA
ELEMENTS
IGNEOUS ROCKS
INFORMATION
KINETICS
METALS
MINERALS
NUMERICAL DATA
PLUTONIC ROCKS
REACTION KINETICS
ROCKS
SEMIMETALS
580400* - Geochemistry- (-1989)