Large-Scale Geometry of Migmatites — Implications for the Seismic Properties of Continental Crust

  • K. Bierbrauer
  • O. Oncken
Conference paper
Part of the Proceedings of the International Conferences on Basement Tectonics book series (ICBT, volume 5)


A quantitative analysis of migmatitic textures is used to describe the complex large-scale geometry of a Variscan migmatite terrain (Argentera massif, western Alps). Small-scale textural variations in migmatites, which can be observed in hand-sample and outcrop scale, closely resemble the overall structural style and kilometer-scale distribution of texturally distinct migmatites within the Argentera basement. Three-dimensional contouring of textural properties in this area suggests a strong influence of migmatization processes on the resulting seismic image of continental crust. A three-dimensional model which has been derived from the geologically reasonable extrapolation of field data shows that regional migmatization mainly results in the formation of “textural gradients”. Such gradients destroy pre-existing fabrics, lithological boundaries and layers of various acoustic impedances. Apart from the typical occurrence of granitic intrusions within the Variscan domain, the strong migmatization of basement gneisses is believed to be largely responsible for the observed seismic transparency in the mid- to upper crustal parts of the internal European Variscides.


Textural Gradient Seismic Property Deep Seismic Reflection Profile Deep Structural Level Argentera Massif 
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Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • K. Bierbrauer
    • 1
  • O. Oncken
    • 1
  1. 1.GeoForschungsZentrum PotsdamPotsdamGermany

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