Illite equilibria in solutions: 1. Phase relationships in the system K sub 2 O-Al sub 2 O sub 3 -SiO sub 2 -H sub 2 O between 25 and 250C

Journal Article · Wed May 01 00:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90313-T· OSTI ID:5979518

Aja, S U; Rosenberg, P E; Kittrick, J A ^[1]

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1. Washington State Univ., Pullman (United States)

Natural illite from Marblehead, Wisconsin (MH), USA, has been equilibrated with 0.2 and 2.0M KCl/KOH and KCl/HCl solutions in the presence of excess kaolinite or microcline and quartz or amorphous silica at temperatures between 25 and 250C and P{sub v} = P{sub H2O}. Reversibility of univariant equilibria was demonstrated by approach from high and low a{sub K{sup +}}/a{sub H{sup +}} vs. log a{sub SiO{sub 2,aq}} diagrams have been constructed defining possible stability fields for kaolinite, microcline, gibbsite (or boehmite or diaspore), muscovite, and four illitic phases. Assuming an R{sup +2}-free stoichiometry, K-content per half cell, estimated from the slopes of univariant lines, are 0.29, 0.50, 0.69, and 0.85 K; these phases are compositional analogs of smectite (S), mixed-layer illite I/S (i.e., IS, ISII) and illite (I), respectively. Illitization reactions are strongly affected by temperature and porewater chemistry. At quartz saturation, direct conversion of smectite or kaolinite to endmember illite can occur at high pH; at low pH, these reactions are unlikely inasmuch as K{sup +} requirements exceed concentrations observed in most natural pore waters. In silica-supersaturated solutions, illitization reactions proceed through crystallization of intermediated phases with compositions between smectite and endmember illite (I).

• OSTI ID: 5979518
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 55:5; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ILLITE
SOLUBILITY
STABILITY
THERMODYNAMIC PROPERTIES
AQUEOUS SOLUTIONS
EQUILIBRIUM
GEOCHEMISTRY
INTERSTITIAL WATER
KAOLINITE
PH VALUE
PHASE STUDIES
QUARTZ
SEDIMENTS
SMECTITE
STOICHIOMETRY
TEMPERATURE EFFECTS
WISCONSIN
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CHEMISTRY
CLAYS
DEVELOPED COUNTRIES
DISPERSIONS
FEDERAL REGION V
GROUND WATER
HYDROGEN COMPOUNDS
MINERALS
MIXTURES
NORTH AMERICA
OXIDE MINERALS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SOLUTIONS
USA
WATER
580000* - Geosciences