Advertisement

Journal of Materials Science

, Volume 22, Issue 6, pp 1913–1918 | Cite as

Cellular intergrowth between quartz and sodium-rich plagioclase (myrmekite) — an analogue of discontinuous precipitation in metal alloys

  • R. Wirth
  • G. Voll
Article

Abstract

Gneissic rocks of the contact aureole of the Traversella Intrusion (N. Italy) reveal a cellular intergrowth of quartz and oligoclase (myrmekite), originating from alkali feldspar grain boundaries. The myrmekite occurs in a temperature range of 500 to 670°C. The size of the cells and the lamellar spacing of the quartz rods increase with rising temperature. A comparison of the characteristic features of myrmekite cells with discontinuous precipitation cells of alloys indicates many similarities between the reactions. A is concluded that the formation of myrmekite is a solid-state reaction; a supersaturated alkali feldspar decomposes into a cellular structure growing behind a moving incoherent grain boundary. Micro probe analyses of the original alkali feldspar, the reaction products, and the volume relationship of the reactants (quartz, sodium-rich plagioclase) show that an ion exchange occurs during the reaction (K+ removed; Na+, Ca2+ and Si4+ added). A model describing the early stages of the formation of myrmekite is presented.

Keywords

Polymer Precipitation Quartz Characteristic Feature Cellular Structure 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    W. A. Deer, R. A. Howie andJ. Zussman, in “Rock-forming minerals”, Vol. 4, (Longman, London, 1963) p. 1.Google Scholar
  2. 2.
    L. Widenfalk,Lithos 2 (1969) 295.Google Scholar
  3. 3.
    H. Ramberg,Neues Jahrb. Miner. Abh. 98 (1962) 14.Google Scholar
  4. 4.
    E. R. Phillips,Lithos 7 (1974) 181.Google Scholar
  5. 5.
    F. K. Drescher-Kaden,Mineralogie und Petrographie in Einzeldarstellungen 1 (1948) 1.Google Scholar
  6. 6.
    G. Voll,Liverpool and Manchester Geol. J. 2 (1960) 503.Google Scholar
  7. 7.
    G. Voll,Fortschritte Mineralogie 60 Beiheft 1 (1982) 207.Google Scholar
  8. 8.
    W. Schreyer,Neues Jahrb. Miner. Abh. 92 (1958) 147.Google Scholar
  9. 9.
    R. Wirth andH. Gleiter,Acta Metall. 29 (1981) 1825.Google Scholar
  10. 10.
    M. Hillert, Met. Trans.3 (1972) 2729.Google Scholar
  11. 11.
    E. Hornbogen,ibid. 3 (1972) 2717.Google Scholar
  12. 12.
    C. Zener,Trans. AIME 167 (1946) 550.Google Scholar
  13. 13.
    R. Wirth,Neues Jahrb. Miner. Abh. 152 (1985) 101.Google Scholar
  14. 14.
    H. Schumann, “Metallographie” (VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1975) p. 58.Google Scholar
  15. 15.
    C. S. Smith,Trans. Amer. Soc. Met. 45 (1953) 533.Google Scholar
  16. 16.
    D. A. Carmichael,Contrib. Mineral. Petrol. 20 (1969) 244.Google Scholar
  17. 17.
    H. Gleiter andB. Chalmers,Progr. Mater. Sci. 15 (1972) 139.Google Scholar
  18. 18.
    W. Q. Kennedy,Schweiz. mineralog. petrogr. Mitt. 11 (1931) 76.Google Scholar
  19. 19.
    R. Wirth,Neues Jahrb. Miner. Abh. 154 (1986) 193.Google Scholar
  20. 20.
    K. N. Tu andD. Turnbull,Acta Metall. 15 (1967) 369.Google Scholar
  21. 21.
    F. Spencer,Mineralog. Magazine 26-7 (1945) 79.Google Scholar

Copyright information

© Chapman and Hall Ltd. 1987

Authors and Affiliations

  • R. Wirth
    • 1
  • G. Voll
    • 2
  1. 1.Institut für Werkstofftechnologie Fachbereich 12.1 Bau 2Universität SaarbrückenSaarbrückenFRG
  2. 2.Mineralogisches Institut der Universität zu KölnKöln 1FRG

Personalised recommendations