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Theoretical studies of the alteration of spodumene, petalite, eucryptite and pollucite in granitic pegmatites: exchange reactions with alkali feldspars

Article Abstract:

Thermodynamic data for minerals and the modified HKF equation of state for aqueous species are used to determine the ratios Na/Li, K/Li, Na/Cs and K/Cs for exchange equilibria among the Li and Cs silicates spodumene, petalite, pollucite, and eucryptite and the alkali feldspars albite and K-feldspar plus quartz at temperatures from 100 degrees to 700 degrees C and pressures from 0.5 to 4kbar in pure water and in chloride solutions. Closed system pegmatite evolution leads to the alteration of encryptite, petallic or spodumene to albite and K-feldspar. Infiltration of the pegmatite by an external fluid with very high Na/Cs and K/Cs ratios is implied by the alternation of pollucite to alkali feldspar.

Author: Williams-Jones, Anthony E., Wood, Scott A.
Publisher: Springer
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1993
Influence, Feldspar, Pegmatites, Pegmatite

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A fluid inclusion study of vug minerals in dawsonite-altered phonolite sills, Montreal, Quebec: implications for HFSE mobility

Article Abstract:

Three Cretaceous age sills with dawsonite-altered phonolite composition intruded the Ordovician limestones of the Montreal Formation in Quebec, Canada. The sills contained vugs which were analysed for fluid inclusion and of which four types were recognized: aqueous liquid-vapor, aqueous- carbonic liquid-vapor and liquid-liquid-vapor, carbonic liquid and liquid- vapor, and; solid-bearing. The vug-filling liquids were suggested to have been exsolved from the sill producing magma. Large concentrations of high field strength elements were noted.

Author: Vard, Eileen, Williams-Jones, Anthony E.
Publisher: Springer
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1993

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The role of phosphorus in rhyolitic liquids as determined from the homogeneous iron redox equilibrium

Article Abstract:

Glasses covering a range of K2O/Al2O3 values and containing 80-85 mol% SiO2 and one mol% Fe2O3 were added with P2O5 and analyzed for phosphorus solution properties in potassium aluminosilicate melts. Variations of homogeneous iron redox equilibrium were employed in the experiments to study the characteristics of silicate melts. The results showed that the redox ratios of iron in phosphorus-bearing peraluminous melts at 85% SiO2 and subaluminous melts at three mol% P2O5 were decreased relative to phosphorus-free liquids.

Author: Gwinn, Rosa, Hess, Paul C.
Publisher: Springer
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1993
Oxidation-reduction reaction, Oxidation-reduction reactions

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Subjects list: Research, Natural history, Montreal, Quebec, Mineralogy, Determinative, Determinative mineralogy, Sills (Geology)
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