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Terminology of “potassium feldspar” and “alkali feldspar”
Ganseki Kobutsu Kagaku, 2023Junji Akai, Satoshi Okamura
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Contributions to Mineralogy and Petrology, 1970
A series of single-phase alkali feldspars in the system Na2O-K2O-Al2O3-SiO2-H2O were crystallized from dehydrated gels at 500 bars and 800° C, in the presence of an aqueous vapor phase, quartz, and corundum. Twenty of these bulk samples were analyzed for K2O and Na2O by atomic absorption spectrophotometry.
W. C. Luth, F. Querol-Su��
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A series of single-phase alkali feldspars in the system Na2O-K2O-Al2O3-SiO2-H2O were crystallized from dehydrated gels at 500 bars and 800° C, in the presence of an aqueous vapor phase, quartz, and corundum. Twenty of these bulk samples were analyzed for K2O and Na2O by atomic absorption spectrophotometry.
W. C. Luth, F. Querol-Su��
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Spinodal Behaviour in an Alkali Feldspar
Nature, 1971THE possibility of spinodal behaviour, as defined by Cahn1,2, occurring in the alkali feldspar system3 has recently been proposed4; we have now produced spinodal textures under controlled hydrothermal conditions.
D. C. OWEN, J. D. C. MCCONNELL
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A nepheline-alkali feldspar geothermometer
Contributions to Mineralogy and Petrology, 1977A nepheline-alkali feldspar geothermometer has been developed which is based on the thermodynamics of an Na—K exchange reaction between nepheline and alkali feldspar. The activities are formulated in terms of site occupancies, and the regular solution model is used to represent non-ideal mixing of the cations on each site.
Powell, Roger, Powell, Marjorie
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Alkali diffusion in plagioclase feldspar
Chemical Geology, 1997Tracer diffusion kinetics at 1 atm pressure under ‘dry’ conditions using 6Li, 41K, and 87Rb in four plagioclase feldspars have been determined. Diffusion profiles were measured using an ion microprobe (SIMS). The Arrhenius parameters and ± 2σ uncertainties for Li, K, and Rb, respectively, in albite, are: pre-exponential factor (log Do) = - 3.8 ± 1.0 ...
Bruno J. Giletti, Timothy M. Shanahan
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Argon-loss by alkali feldspars
Geochimica et Cosmochimica Acta, 1988Abstract Ar-loss is generally thought to preclude the use of alkali feldspars for dating old rocks by the K-Ar method, and has been thought to occur via structural features such as the boundaries of perthite lamellae or twins. We have done a 40 Ar- 39 Ar step-heating study of a suite of alkali feldspars from the Klokken syenite intrusion (U-Pb age ...
I Parsons +3 more
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Homogeneity in alkali feldspars
Mineralogical Magazine and Journal of the Mineralogical Society, 1968SummaryCurves relating spacing, Or content, and structural state of alkali feldspars are reviewed. Discrepancies between the compositions of heated natural perthitic alkali feldspars determined by this method and by chemical analysis are discussed and shown to be largely consistent with incomplete homogenization.
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Nature, 1966
IT has long been assumed that the degree of ordering between silicon and aluminium in the tetrahedral sites of feldspars is related to the conditions of formation of the minerals. A direct test of this idea has, up to the present, been hampered by the lack of an easy method of measuring the degree of order in a genetically related suite of feldspars ...
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IT has long been assumed that the degree of ordering between silicon and aluminium in the tetrahedral sites of feldspars is related to the conditions of formation of the minerals. A direct test of this idea has, up to the present, been hampered by the lack of an easy method of measuring the degree of order in a genetically related suite of feldspars ...
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Feldspar Megacrysts in Alkali Basalts
Geological Society of America Bulletin, 1974Feldspar megacrysts from pyroclastic ejecta of four alkaline basaltic centers were analyzed by atomic absorption spectrophotometry. Anorthoclase is present at three localities, oligoclase at two localities, and andesine at one locality. These crystals are interpreted as phenocrysts of the basalt that crystallized under high-pressure conditions.
A. W. LAUGHLIN +2 more
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Alkali interdiffusion in alkali feldspars
2014Cation exchange experiments were conducted at 800°C to 1000°C and 1 bar using oriented plates of sanidine and NaCl-KCl salt mixtures as starting material. The formation of interdiffusion fronts propagating into the sanidine by Na-K-interdiffusion on the alkali sublattice was observed.
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