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The microfabric of a chemically weathered granite

  • Baynes J. 
  • Dearman W. R. 
Article

Summary

A scanning electron microscope has been used to observe the microfabric changes in granite that are brought about by weathering. The initial ingress of weathering agencies occurs along primary cracks and pores and open cleavages and results in decomposition and solution along structurally controlled planes in feldspars, the decomposition and expansion of the biotite lattice, and solution and microfracturing of quartz.

In terms of the fundamental material nature of weathered granite, the initial stages of weathering are dominated by the opening of grain boundaries, microfracturing and the development of an intragranular porosity in feldspars. The later stages of weathering are dominated by the variable nature of the clay weathering product.

Keywords

Kaolinite Weathering Kaolin Gibbsite Weathered Granite 

La Microstructure D’un Granite Altéré Chimiquement

Résumé

Un microscope électronique à balayage a été utilisé pour l’observation des changements de microstructure qui affectent un granite soumis à l’altération météorique. La première avancée de l’altération se produit le long de craquelures et de pores préexistants et de clivages ouverts; elle aboutit à la décomposition et à la dissolution des feldspaths le long de plans correspondant à la structure, à la décomposition et à l’expansion du réseau de la biotite, à la dissolution et à la microfracturation du quartz.

En ce qui concerne la nature fondamentale du granite altéré, les premières phases de l’altération sont dominées par l’ouverture des surfaces de séparation des grains, la microfracturation et le développement d’une porosité intragranulaire dans les feldspaths. Les phases suivantes sont dominées par la nature variable de l’argile d’altération.

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Copyright information

© International Assocaition of Engineering eology 1978

Authors and Affiliations

  • Baynes J. 
    • 1
  • Dearman W. R. 
    • 1
  1. 1.Engineering Geology Unit, Department of GeologyUniversity of Newcastle upon TyneU.K.

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