Abstract
Chess-board (“tiled”) microcline crystals from a nepheline-bearing syenite from Ilimaussaq, W. Greenland, were investigated using transmission electron microscopy (TEM) and were found to consist of a mosaic of slightly misoriented domains, which bear no obvious relationship to the optical microstructure. Part of the misorientation of most pairs of neighbouring domains involves a small rotation about c. However, some are related to adjacent domains by the albite twin law, the pericline law, or diagonal association. This microcline could have crystallized with triclinic symmetry which could account for the differences between the microstructure of this microcline and M-twinned microcline. Metasomatism may explain both the optical microscope and TEM scale structures of this microcline. Examination of the electron diffraction patterns of areas of microcline which contain both diagonally associated and twinned domains draw attention to the fact that each of the few orientations in an M-twinned crystal is related to one of the other orientations by diagonal association. The formation of common cross-hatch twinned microstructures are discussed with reference to diagonal association.
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References
Akizuki M (1972) Electron-microscopic investigation of microcline twinning. Amer Mineral 57:797–808
Battey MH (1955) Alkali metasomatism and the petrology of some keratophyres. Geol Mag 92:104–126
Brown WL, Williame C (1974) An explanation of exsolution orientations and residual strain in cryptoperthites. In: Mackenzie WS, Zussman J (eds). The Feldspars. Manchester: Manchester University Press, Manchester, pp 440–459
Brown WL, Williame C, Guillemin C (1972) Exsolution selon l'association diagonale dans une cryptoperthite: étude par microscopie électronique et diffraction des rayons X. Bull Soc Fr Mineral Crystallogr 95:429–436
Callegari E, Pieri R de (1967) Crystallographic observations on some chess-board albites. Schweiz Mineral Petrogr Mitt 47:99–110
Carter S, Champness PE (1980) The diagonal association in alkali feldspars. Electron Microscopy (Proceedings of the International Congress on Electron Microscopy) 1:454–455
Fitz Gerald JD, Etheridge MA, Vernon RH (1983) Dynamic recrystallization in a naturally deformed albite. Textures and Microstructures 5:219–237
Fitz Gerald FD, McLaren AC (1982) The microstructures of microcline from some granitic rocks and pegmatites. Contrib Mineral Petrol 80:219–229
Gates RM, Sheerer PE (1963) The petrology of the Nonewaug granite, Connecticut. Am Mineral 48:1040–1069
Laves F (1950) The lattice of microcline and other potash feldspars. J Geol 58:548–571
Lorimer GW, Champness PE (1973) The origin of the phase distribution in two perthitic alkali feldspars. Philos Mag 28:1391–1403
McLaren AC (1978) Defects and microstructures in feldspars. In: Chemical Physics of Solids and their Surfaces 7. The Chemical Society, London, pp 1–30
Smith JV (1974) Feldspar Minerals. Springer, Berlin Heidelberg New York
Starkey J (1957) Chess-board albite from New Brunswick, Canada. Geol Mag 96:141–145
Tibbals JE, Olsen A (1977) An electron microscope study of some twinning and exsolution textures in microcline amazonites. Phys Chem Minerals 1:313–324
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Smith, K.L., McLaren, A.C. TEM investigation of a microcline from a nepheline syenite. Phys Chem Minerals 10, 69–76 (1983). https://doi.org/10.1007/BF00309587
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DOI: https://doi.org/10.1007/BF00309587