Illite equilibria in solutions: 2. Phase relationships in the system K sub 2 O-MgO-Al sub 2 O sub 3 -SiO sub 2 -H sub 2 O

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

OSTI ID:6140309

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

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

The stability of the Marblehead illite has been investigated in the five-component system K{sub 2}O-MgO-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O in the presence of kaolinite and microcline. The mica-like solubility-controlling phases (K{sub x}(Mg{sub y}Al{sub 2{minus}y})(Al{sub x{minus}y}Si{sub 4{minus}(x{minus}y)}) O{sub 10}(OH){sub 2}) identified include (1) smectite x = 0.29 {plus minus} 0.04, y = 0.26 {plus minus} 0.02; (2) illite x = 0.50 {plus minus} 0.05, y = 0.22 {plus minus} 0.14; (3) illite x = 0.69 {plus minus} 0.08, y = 0.16 {plus minus} 0.03; (4) illite x = 0.85 {plus minus} 0.05, y = 0.12 {plus minus} 0.04; and (5) muscovite. Possible stability regions have been defined for these solubility-controlling phases using isothermal isobaric log a{sub Mg{sup +2}}{sup {1/2}}/a{sub H{sup +}} vs. log a{sub K{sup +}}/a{sub H{sup +}} diagrams. When illite stability is referred to the quaternary system K{sub 2}O-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O, the effect of (R{sup +2}){sup VI} substitution is neglected. The error inherent in this simplification has been estimated. Inasmuch as a four-fold increase in a{sub Mg{sup 2+}} shifts the illite-smectite-kaolinite-solution invariant point by less than 0.3 log units, stability relationships in the quaternary system provide an adequate representation of illite solution equilibria, to a first approximation, However, the error caused by neglecting Mg{sup 2+} is close to or within experimental error. Thus, a more precise determination of the effect of Mg{sup +2} on illite solution equilibria may not be possible using the solution equilibration method.

• OSTI ID: 6140309
• 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
KAOLINITE
PHASE STUDIES
SMECTITE
STOICHIOMETRY
TEMPERATURE EFFECTS
WISCONSIN
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CHEMISTRY
CLAYS
DEVELOPED COUNTRIES
DISPERSIONS
FEDERAL REGION V
MINERALS
MIXTURES
NORTH AMERICA
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SOLUTIONS
USA
580000* - Geosciences