Polysynthetic twin width distributions in anorthoclase

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Authors:Gray, Norman H.; Anderson, James B.
Author Affiliations:Primary:
Univ. Connecticut, Inst. Material Sci., Storrs, CT 06268, United States
Volume Title:Lithos (Oslo)
Source:Lithos (Oslo), 15(1), p.27-37. Publisher: Elsevier, Amsterdam, International. ISSN: 0024-4937
Publication Date:1982
Note:In English. 11 refs.; illus. incl. 3 tables
Summary:The widths of just under 7000 albite and pericline lamellae were measured in a suite of 20 polysynthetically-twinned anorthoclase megacrysts collected at two sites in New Mexico. The majority of the twins were formed during the inversion of the anorthoclase crystals from their high-T monoclinic modification to their present triclinic form. Textural evidence suggests that a few of the lamellae postdate the transformation and are mechanical in origin. Twin density is exceedingly inhomogeneous on all scales, and the related black and white lamella sets are unequally developed even within a single crystal. This type of inhomogeneity is probably a common feature of all inversion twinning, since it arises as a natural consequence of the complex and rapidly changing stress conditions within a crystal undergoing transformation. [G.R.]
Subjects:Albite; Alkali basalts; Alkali feldspar; Anorthoclase; Basalts; Crystal growth; Dimensions; Feldspar group; Framework silicates; Geometry; Igneous rocks; Lava flows; Megacrysts; Minerals; Plagioclase; Silicates; Twinning; Variations; Volcanic rocks; New Mexico; United States; Bandera Crater Field; Pericline
Abstract Numbers:82M/4567
Record ID:1983049979
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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