Mineralogy and Petrology

, 97:251 | Cite as

Perthite microstructure in magmatic alkali feldspar with oscillatory zoning; Weinsberg Granite, Upper Austria

  • Rainer AbartEmail author
  • Elena Petrishcheva
  • Stefan Käßner
  • Ralf Milke
Original Paper


Feldspar megacrysts from the Weinsberg granite (Moldanubian Zone) show oscillatory zoning with respect to the albite- and orthoclase components. All growth zones show perthitic exsolutions which take the form of bleb- and lens shaped albite-rich precipitates in an orthoclase-rich host. The average sizes and shapes of the precipitates show systematic variation with the integrated bulk compositions of the respective growth zones. The precipitates are abundant and relatively small in growth zones with intermediate bulk composition (Or50Ab41An09 - Or80Ab18An02), and they are less abundant and larger in more orthoclase-rich zones (Or88Ab11An01). Small precipitates have a relatively high aspect ratio, whereas the large precipitates in the potassium-rich zones are more spherical. The relation between microstructure and integrated bulk composition suggests that exsolution and subsequent growth and coarsening occurred by different mechanisms in the respective growth zones. Numerical modeling shows that rapid growth of precipitates over extended periods of time and attainment of relatively large final size is favored, if only few nuclei are formed in an oversaturated host. In contrast, precipitates can grow rapidly only over limited time intervals and remain relatively small, if abundant nuclei are present. During cooling of the oscillatorily zoned alkali-feldspar, exsolution started at relatively high temperatures in growth zones of intermediate integrated bulk composition as compared to exsolution in the more orthoclase-rich growth zones. Irrespective of whether exsolution occurred by spinodal decomposition or by nucleation at relatively high temperatures in the growth zones of intermediate integrated bulk composition, it produced abundant nuclei and resulted in relatively small precipitates. In contrast, comparatively few nuclei were formed in the orthoclase-rich growth zones resulting in large precipitates. The Na/K partitioning between precipitates and the host is independent of the integrated bulk composition of the respective growth zone reflecting re-equilibration during cooling down to relatively low temperatures (< 400°C). The shape of the precipitates probably has evolved from an initially lamellar or spindle-like geometry with high aspect ratio to more isometric, spheroidal shapes during precipitate growth and coarsening. Host/precipitate interfaces served as fluid pathways during late stage deuteric alteration.


Growth Zone Spinodal Decomposition Oscillatory Zoning Precipitate Size Alkali Feldspar 
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.



We want to thank Friedrich Koller for providing the samples and Lukas Keller for his help on the scanning electron microscope. Funding by the Deutsche Forschungsgemeinschaft, project AB 741/3-1 is gratefully acknowledged. We are grateful to two anonymous reviewers for their valuable comments and advice.


  1. Abart R, Petrishcheva E, Wirth R, and Rhede D (2009) Exsolution by spinodal decomposition: II: perthite formation during slow cooling of anatexites from Ngornghoro, Tanzania. Am J Sci 309:450–475CrossRefGoogle Scholar
  2. Behrens H, Johannes W, Schmalzried H (1991) On the mechanisms of cation diffusion-processes in ternary feldspars. Phys Chem Miner 17:62–78CrossRefGoogle Scholar
  3. Brown W, Parsons I (1984) Exsolution and coarsening mechanisms and kinetics in an ordered cryptoperthite series. Contrib Mineral Petrol 86:3–18CrossRefGoogle Scholar
  4. Brown W, Parsons I (1988) Zoned ternary feldspars in the Klokken intrusion: exsolution microtextures and mechanisms. Contrib Mineral Petrol 98:444–454CrossRefGoogle Scholar
  5. Brown W, Parsons I (1989) Alkali feldspars—ordering rates, phase-transformations and behaviour diagrams for igneous rocks. Min Mag 53:25–42CrossRefGoogle Scholar
  6. Cahn JW (1968) Spinodal decomposition. Trans Metall Soc AIME 242(2):166–180Google Scholar
  7. Cahn JW, Hilliard J (1958) Free energy of a nonuniform system. I. Interfacial free energy. J Chem Phys 28(2):258–267CrossRefGoogle Scholar
  8. Christoffersen R, Schedl A (1980) Microstructure and thermal history of cryptoperthites in a dike from big bed. Am Mineral 65:444–448Google Scholar
  9. Christoffersen R, Yund R, Tullis J (1983) Inter-diffusion of K and Na in alkali feldspars: diffusion couple experiments. Am Mineral 68:1126–1133Google Scholar
  10. Evangelakakis C, Kroll H, Voll G, Wenk HR, Hu M, Kopcke J (1993) Lowtemperature coherent exsolution in alkali feldspar from high grade metamorphic rocks of Sri-Lanka. Contrib Mineral Petrol 114:519–532CrossRefGoogle Scholar
  11. Finger F, von Quadt A (1992) Wie alt ist der Weinsberg Granit? U/Pb versus Rb/Sr Geochronologie. Mitt Oesterr Mineral Ges 137:83–86Google Scholar
  12. Fitz-Gerald J, Parsons I, Cayzer N (2006) Nannotunnels and pull-aparts: defects of exsolution lamellae in alkali feldspar. Am Mineral 91:772–783CrossRefGoogle Scholar
  13. Koller F, Kloetzli U (1988) The evolution of the South Bohemian Pluton. In: Breiter K (ed) Genetic significance of phosphorus in fractionated granites. Excursion guide, IGCP373. Czech Geological Survey, Prague, pp 11–14Google Scholar
  14. Kuhl E, Schmid DW (2007) Computational modeling of mineral unmixing and growth—an application of the Cahn-Hilliard equation. Comput Mech 39:439-451CrossRefGoogle Scholar
  15. Lifshitz IM, Slyozov VV (1961) The kinetics of precipitation from supersaturated solid solutions. J Phys Chem Solids 19:35–50CrossRefGoogle Scholar
  16. Menna M, Tribaudino M, Renzulli A (2008) Al-Si order and spinodal decomposition texture of a sanidine from igneous clasts of Stromboli (Southern Italy): insights into the timing between the emplacement of a shallow basic sheet intrusion and the eruption of related ejecta. Eur J Mineral 20:183–190CrossRefGoogle Scholar
  17. Nauman E, He D (2001) Nonlinear diffusion and phase separation. Chem Eng Sci 56(6):1999–2018CrossRefGoogle Scholar
  18. Parsons I (1978) Feldspars and fluids in cooling plutons. Min Mag 42:1–17CrossRefGoogle Scholar
  19. Parsons I, Brown W (1983) A TEM and microprobe study of a 2-perthite alkali gabbro—implications for the ternary feldspar system. Contrib Mineral Petrol 82:1–12CrossRefGoogle Scholar
  20. Parsons I, Lee MR (2009) Mutual replacement reactions in alkali feldspars I: microtextures and mechanisms. Contrib Mineral Petrol 157:641–661CrossRefGoogle Scholar
  21. Parsons I, Thompson P, Lee M, Cayzer N (2005) Alkali feldspar microtextures as provenance indicators in siliciclastic rocks and their role in feldspar dissolution during transport and diagenesis. J Sediment Res 75:921–942CrossRefGoogle Scholar
  22. Parsons I, Magee CW, Allen CM, Shelley JMG, Lee M (2009) Mutual replacement reactions in alkali feldspars II: trace element partitioning and geothermometry. Contrib Mineral Petrol 157:663–687CrossRefGoogle Scholar
  23. Petrishcheva E, Abart R (2009) Exsolution by spinodal decomposition: I: evolution equation for binary mineral solutions with anisotropic interface energy. Am J Sci 309:431–449CrossRefGoogle Scholar
  24. Petrovic R (1973) The effect of coherency stress on the mechanism of the reaction Albite + K +  = K - Feldspar + Na +  and on the mechanical state of the resulting feldspar. Contrib Mineral Petrol 41:151–170CrossRefGoogle Scholar
  25. Robin P (1974) Stress and strain in cryptoperthite lamellae and the coherent solvus of alkali feldspar. Am Mineral 59:1299–1318Google Scholar
  26. Smith J, Brown W (1988) Feldspar minerals: crystal structures, physical, chemical, and microtextural properties, vol 1. Springer, BerlinGoogle Scholar
  27. Vellmer C, Wedepohl KH (1994) Geochemical characterisation and origin of granitoids from the South Bohemian Batholith in Lower Austria. Contrib Mineral Petrol 118:13–32CrossRefGoogle Scholar
  28. Yund R (1984) Feldspars and feldspathoids, chapter Alkali feldspar exsolution: kinetics and dependence on alkali interdiffusion. Reidel, Dordrecht, pp 281–315Google Scholar
  29. Yund R, Chapple W (1980) Thermal histories of 2 lava flows estimated from cryptoperthite lamellar spacings. Am Mineral 65:438–443Google Scholar
  30. Yund R, Davidson P (1978) Kinetics of lamellae coarsening in cryptoperthite. Am Mineral 63:470–477Google Scholar
  31. Yund R, McLaren A, Hobbs B (1974) Coarsening kinetics of exsolution microstructure in alkali feldspar. Contrib Mineral Petrol 48:45–55CrossRefGoogle Scholar
  32. Yund R, Ackermand D, Siefert F (1980) Microstructures in the alkali feldspars from the granulite complex of finnish lapland. Neues Jahrb Mineral Monatsh 3:109–117Google Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Rainer Abart
    • 1
    Email author
  • Elena Petrishcheva
    • 2
  • Stefan Käßner
    • 2
  • Ralf Milke
    • 2
  1. 1.Department of Lithosphere ResearchUniversität WienWienAustria
  2. 2.Institute of Geological SciencesFreie Universität BerlinBerlinGermany

Personalised recommendations