Chemical and structural variations at augite (100) deformation twin boundaries

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doi: 10.2138/am.2007.2565
Authors:Zhang, Shouliang; Veblen, David R.
Author Affiliations:Primary:
Johns Hopkins University, Department of Earth and Planetary Sciences, Baltimore, MD, United States
Volume Title:American Mineralogist
Source:American Mineralogist, 92(11-12), p.1833-1837. Publisher: Mineralogical Society of America, Washington, DC, United States. ISSN: 0003-004X
Publication Date:2007
Note:In English. 23 refs.; illus., incl. 2 tables
Summary:It is commonly found that deformation twinning response to plastic deformation results in structural variations at a twin boundary (TB). Chemical heterogeneity at a TB, compared to the host, however, has rarely been reported. An augite sample with a high density of deformation twinning lamellae from Lofoten, Norway was examined using high-resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) techniques to characterize both structural and chemical variations at a TB. HRTEM experimental results combined with high-resolution image simulation unambiguously resolve the augite deformation TB structure as a half unit cell of orthopyroxene. EFTEM images at TB demonstrate that Ca is depleted, whereas Fe is enriched at this sub-nanometer scale (0.9 nm) interface. In addition, distance-least-squares (DLS) program was applied to verify that the TB structure is geometrically stabilized by substitution of Fe for Ca. [R.A.H.]
Sections:Mineral data
Mineral Groups:Single-chain silicates
Subjects:Alkaline earth metals; Augite; Calcium; Chain silicates; Clinopyroxene; Crystal chemistry; Crystal growth; Crystal structure; Deformation; High-resolution methods; Iron; Metals; Pyroxene group; Silicates; Substitution; TEM data; Twinning; Variations; Europe; Lofoten Islands; Nordland Norway; Norway; Scandinavia; Western Europe
Abstract Numbers:08M/0017
Record ID:2008014019
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, copyright, Mineralogical Society of America, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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