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Foliation index determination for fine-grained metamorphic rocks

  • Tsidzi K. E. N. 
Article

Abstract

The fine grain size of rocks such as slates, phyllites and hornfelses limits the accurate determinations of their foliation index values using the optical microscope. An experimental study has therefore been undertaken for a more relevant approach to evaluating the index. X-ray diffractometry on rock specimens at extreme orientations is ideal.

The rock types studied fit well into a proposed classification scheme. This reaffirms that foliation index is a reliable parameter for the quantitative fabric characterization of metamorphic rocks which bears a practical significance to their engineering performance.

Keywords

Chlorite Prefer Orientation Metamorphic Rock Shape Factor Hand Specimen 

Détermination d'un indice de foliation dans les roches métamorophiques à grain fin

Résumé

La finesse des grains de roches telles que les schistes, phyllades ou cornéenes empêche une bonne dêtermination de laur indices de foliation au moyen du microscope optique. Une étude expérimentale a donc été entreprise pou trouver une meilleure approche de cet indice. L'idéal est la diffractométie RX effectuée sur des échanitilloons de roches parfaitement orientés.

Les roches étudiées trouvent ensuite place dans une classification, ce qui prouve une nouvele fois que l'indice de foliation est un paramétre fiable pour caractériser quantitativement la structure des roches métamorphiques, qui a elle-même une influence déterminante sur leur comportement mécanique.

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References

  1. ADLER I. and AXELROD J.M., 1957: Relflecting Curved-crystal X-ray Spectrograph: A Device for the Analysis of Small Mineral Samples. Econ. Geol., Vol. 6, pp. 694–701.CrossRefGoogle Scholar
  2. ATTEWELL P.B. and FARMER I.W., 1976: Principles of Engineering Geology. Chapman and Hall, London, 1045 p.CrossRefGoogle Scholar
  3. ATTEWELL P.B. and SANDFORD M.R. 1974: Intrinsic Shear Strength of a Brittle Anisotropic Rock. Part 1. Int. J. Rock Mech. Min. Sci. and Geomech. Abstr. Vol. 11, pp. 423–451.CrossRefGoogle Scholar
  4. ATTEWELL P.B. and TAYLOR R.K. 1969: A Microtextural Interpretation of a Welsh Stale. Int. J. Rock Med. Min. Sci. and Geomech. Abstr., Vol. 6, pp. 423–428.CrossRefGoogle Scholar
  5. BAYLISS P., BERRY L.G., MROSE M.E. and SMITH D.K., 1980: Mineral Powder Diffraction File. JCPDS Int. Centre for Diffraction Data, U.S.A., 484 p.Google Scholar
  6. CHERNOCK W.P. and BECK P.A., 1952: Analysis of Certain Errors in the X-ray Reflection Method for Quantitative Determination of Preferred Orientation. J. Appl. Phys. Vol. 23, pp. 341–345.CrossRefGoogle Scholar
  7. FAYED L.A., 1967: An X-ray Diffractometry Technique for Preferred Orientation Studies in Rocks. Int. J. Rock Mech. Min. Sci. and Geomech. Abstr., Vol. 4, pp. 101–114.CrossRefGoogle Scholar
  8. GILLOTT J.E., 1969: Study of the Fabric of Fine-grained Sediinents with Scanning Electron Microscope. J. Sed. Petrology. Vol. 39, pp. 90–105.Google Scholar
  9. GILLOTT J.E., 1970: Fabric of Leda Clay Investigated by Optical, Electron-Optical and X-ray Diffraction Methods. Enging. Geol. Vol. 4. pp. 121–132.CrossRefGoogle Scholar
  10. GIPSON M., 1965: Application of the Electron Microscope to the Study of Particle Orientation and Fissility in Shale. J. Sed. Petrology, Vol. 35, pp. 408–414.Google Scholar
  11. HIGGS D.B., FRIEDMAN M. and GEBHART J.E., 1960: Petrofabric Analysis by means of the X-ray Diffractometer. Mem. Geol. Soc. Am., Vol. 79, pp. 275–292.Google Scholar
  12. MARTIN R.T., 1966: Quantitative Fabric of Wet Kaolinite. Clays and Clay Miner. Vol. 14, pp. 247–287.CrossRefGoogle Scholar
  13. MORGENSTERN N.R. and TCHALENKO J.S., 1967: The Optical Determination of Preferred Orientation in Clays and its Application to the Study of Microstructure in Consolidated Kaolin. Parts I and II. Proc. Roy. Soc., Vol. A 300, pp. 218–250.CrossRefGoogle Scholar
  14. MOSELEY, H.G.J., 1913: The High Frequency Spectra of the Elements. Phil. Mag., Vol. 26, p. 1024.CrossRefGoogle Scholar
  15. ODOM I.E., 1967: Clay Fabric and its Relation to Structural Properties in Mid-Continent Pennsylvanian Sediments. J. Sed. Petrology, Vol. 37, pp. 610–623.Google Scholar
  16. SORBY, H.C., 1853: On the Origin of Slaty Cleavage. Edin. New Phil. J., Vol. 55, pp. 137–148.Google Scholar
  17. SPRY, A., 1969: Metamorphic Textures. Pergamon Press Ltd., Oxford, 350 p.Google Scholar
  18. TSIDZI K.E.N., 1986: A quantitative Petrofabric Characterization of Metamorphic Rocks. Bull. Int. Assoc. Engng. Geol., No. 33.Google Scholar

Copyright information

© International Assocaition of Engineering eology 1987

Authors and Affiliations

  • Tsidzi K. E. N. 
    • 1
  1. 1.School of MinesUniversity of Science and TechnologyKumasiGhana

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