Browse > Article

A Study on Microstructures and Chemistry of Anorthoclase Using Electron Microscopy  

이영부 (한국기초과학지원연구원)
김윤중 (한국기초과학지원연구원)
이석훈 (한국기초과학지원연구원)
이정후 (전북대학교 지구환경과학과)
Publication Information
Journal of the Mineralogical Society of Korea / v.16, no.3, 2003 , pp. 233-243 More about this Journal
Abstract
Microstructures and chemistry of anorthoclase, a high-temperature phase of alkali feldspars, were studied using EPMA and TEM. BSE images of anorthoclase displayed mixtures of Na-rich areas and K-rich areas forming lamella of various sizes. EPMA analysis indicated that the Na-rich area is composed of Ab: 81%, Or: 3% and An: 11% in average, while the K-rich area is composed of Ab: 45%, Or: 44% and An: 11 % in average. TEM analysis revealed albite with Albite twins in the Na-rich area, contrasting to mixtures of albite with fine Albite twins and orthoclase without twins, forming regular lamella of about 100 nm sizes, in the K-rich area. The [001] electron diffraction pattern of the K-rich area also indicated coexistence of the two phases. While streaking parallel to the (010)$^{*}$ direction appeared only in albite due to the twin structure, streaking parallel to the $(100)^{ *}$ direction appeared both in albite and orthoclase, probably due to strain on the interface as well as order-disorder phenomena of Al and Si. It is suggested that the reverse orientation of albite and orthoclase is caused by pole switching to reduce strain on their interfaces. Based on these observations and analyses, the mineral studied is identified as lower-temperature cryptoperthite rather than high-temperature anorthoclase, which has a midium degree of Al-Si ordering and $400^{\circ}C$∼$600^{\circ}C$ of estimated temperatures for the microstructure formation.
Keywords
anorthoclase; lamella; anorthoclase; lamella; Albite twin; Al-Si order-disorder; strain;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Aizu, K. (1970) Possible species of ferromagnetic, ferroelectric and ferroelastic crystals, Phys. Rev. B2, 754-772.
2 Salje, E.K.H. (1990) Phase transitions in Ferroelastic and Co-elastic Crystals, Cambridge Univ. Press, 281pp.
3 Thompson, J.B. and Waldbaum, D.R. (1969) Mixing properties of sanidine crystalline solutions. III. Calculations based on two-phase data, Am. Mineral, 54, 811-838.
4 Wadhawan, V.K. (1982) Ferroelasticity and related properties of crystals, Phase Transitions, 3, 3-103.
5 Sipling, P.J. and Yund, R.A. (1976) Experimental determination of the coherent solvus for sanidinehigh albite, Am. Mineral, 61, 897-906.
6 Ribbe P.H. (ed.) (1983) Feldspar Mineralogy, 2nd ed., Review in Mineralogy, 2, Mineral. Soc. Am, 362pp.
7 Willaime, C., Brown, W.L., and Gandais, M. (1976) Physical aspects of exsolution in natural alkali feldspars: In, Wenk, H.R. (Eds.) Electron Microscopy in Mineralogy, Springer Berlin, 248-257.
8 Kim, Y-J. and Lee, Y-B. (2003) XRD and TEM investigation of structures and phase transformations in albite, J. Mineral. Soc. Korea, 16, 91-106.
9 Martin, R.F. (1974) Controls of ordering and subsoildus phase relation in the alkali feldspar: In, MacKenzie, W.S. and Zussman, J. (Eds.) The feldspars, Manchester Univ. Press: Manchester, 313-336.
10 Deer, W.A., Howie, R.A., and Zussman, J. (2001) Rock-Forming Minerals, Vol. 4A, 2nd eds., Framework Silicates: Feldspars, The Geological Society, London, 972pp.
11 Brown, W.L. and Persons, I. (1984) Exsolution and coarsening mechanism and kinetics in an ordered cryptoperthite series, Contrib. Mineral. Petrol., 96, 3-18.
12 Kroll, H. and Ribbe, P.H. (1987) Determining (Al, Si) distribution and strain in alkali feldspar using lattice parameter and diffraction peaks position, A review, Am. Mineral, 72, 791-506.
13 Brown, W.L. and Willaime, C. (1974) An explanation of exsolution orientations and residual strain in cryptoperthites: In, MacKenzie, W.S. and Zussman, J. (Eds.) The feldspars, Manchester Univ. Press: Manchester, 440-459.
14 Kroll, H. (1971) Determination of Al, Si distribution in alkali feldspars from x-ray powder data, N. Jahrb. Mineral. Monatsh., 91-94.
15 Xu, H., Veblen D.R., Buseck P., and Ramakrishna B.L. (2000) TEM and SFM of exsolution and twinning in an alkali feldspar, Am. Mineral, 85, 509-513.
16 Smith, J.V. and Brown, W.L. (1988) Feldspar Minerals, Springer-Verlag, 828pp.
17 Smith, J.V. (1974) Feldspar Minerals. I. Crystal structure and Physical Properties, Springer-Verlag: Heidlberg, 627pp.
18 Lee, Y-B. and Kim Y-J. (1999) An investigation of lattice parameter measurement of inorganic crystals by electron diffraction patterns, J. Korean Society of Electron Microscopy, 29, 75-81.
19 Parsons, I. (ed.) (1994) Feldspars and Their Reactions, Kluwer Academic Publishers, 650pp.
20 Stewart, D.B. and Wright, T.L. (1974) Al/Si order and symmetry of natural alkali feldspars, and the relationship of stained cell parameter to bulk composition, Bull. Soc. franc Mineral Cristallogr, 97, 356-377.