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Microscopic cordierite in fused Torridonian arkose

Wyllie, P. J. (1959) Microscopic cordierite in fused Torridonian arkose. American Mineralogist, 44 (9-10). pp. 1039-1046. ISSN 0003-004X.

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Progressive thermal metamorphism of Torridonian arkose by a picrite sill in Soay (Hebrides) has culminated in extensive fusion. Microlites of cordierite were precipitated from the liquid as colorless, six-sided prisms (maximum dimension 0.06 mm.) with abundant magnetite inclusions. Refractive indices of the cordierite lie between 1.529 and 1.541, and (-) 2V is small. The cordierite is frequently twinned on (110), and rare cruciform twins are also present. The latter have (021) or (101) as the probable twin plane. Only (110) and (130) have been reported previously as cordierite twin planes. The distortion index, Δ (degree of distortion from hexagonal symmetry, measured by x-ray powder diffraction), is 0.08. From independent evidence, the maximum P_(H2O) was 430 kg/cm^2, and the minimum temperature interval of cordierite crystallization was 1025° C. to 935° C. If P_(H2O) were less than 430 kg/cm^2, the estimated crystallization temperatures would be higher. A useful temperature scale may be established by: (1) correlation of the structural state of cordierite with estimated temperature and pressure of water vapor in buchites, and (2) extension of hydrothermal studies on synthetic cordierites. Both approaches are required because the crystallization history of cordierite may affect its structural state. It is probable that the crystallization histories of cordierites in most buchites followed similar patterns.

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Additional Information:© 1959 Mineralogical Society of America. Manuscript received January 26, 1959. Contribution No. 58-70, The Pennsylvania State University, College of Mineral Industries, Department of Geophysics and Geochemistry, University Park, Pennsylvania. The work on which this paper is based was begun in the Department of Geology, University of St. Andrews, Scotland, and completed in the Department of Geophysics and Geochemistry, The Pennsylvania State University. My thanks are due to Dr. H. I. Drever and to Mr. R. Johnston for advice and criticism during the early stages, and to Dr. O. F. Tuttle for later criticism.
Issue or Number:9-10
Record Number:CaltechAUTHORS:20160121-135229197
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63843
Deposited By: Tony Diaz
Deposited On:21 Jan 2016 22:48
Last Modified:03 Oct 2019 09:32

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