Na-K interdiffusion in alkali feldspar melts

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doi: 10.1016/S0016-7037(98)00226-9
Authors:Freda, Carmela; Baker, Don R.
Author Affiliations:Primary:
Universita La Sapienza, CNR Centro di Studio per gli Equilibri Sperimentali in Minerali e Rocce, Rome, Italy
Other:
McGill University, Canada
Volume Title:Geochimica et Cosmochimica Acta
Source:Geochimica et Cosmochimica Acta, 62(17), p.2997-3007. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037
Publication Date:1998
Note:In English. 57 refs.; illus., incl. 2 tables
Summary:The results are presented of measurements of Na-K interdiffusion coefficients between albite and orthoclase melts under different conditions of T, P and H2O content. Since Na and K diffusivities may be independent of melt composition from basalt to rhyolite, the resulting data on amorphous feldspar may be extended over a wide magma compositional range. The experiments were made under conditions of 1.0 GPa and Texp = 800 and 1600°C, and at 2.0 GPa and 1400°C in anhydrous melts, and in hydrous 5.5 wt.% H2O melts at 1.0 GPa, 1200 and 1400°C. The results show that the only diffusive transport was the exchange of Na and K cations. The alkali interdiffusion coefficients are four orders of magnitude greater than those estimated of network-former cations in melts of the same composition. P did not have a measurable effect on Na-K interdiffusion at 1400°C. Alkali diffusion in both anhydrous and hydrous melts can be described by Arrhenius equations. The Na-K interdiffusion coefficients may describe the maximum rates of alkali diffusion over a wide range of melt compositions in the crust and upper mantle. [R.K.H.]
Sections:Experimental mineralogy
Subsections:Silicates
Subjects:Albite; Alkali feldspar; Alkali metals; Diffusion; Experimental studies; Feldspar group; Framework silicates; Geochemistry; Glass materials; High pressure; High temperature; Laboratory studies; Melts; Metals; Orthoclase; P-T conditions; Plagioclase; Potassium; Pressure; Silicates; Sodium; Synthesis; Temperature
Abstract Numbers:99M/3767
Record ID:1999021334
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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