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.
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.
Similar content being viewed by others
References
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.
ATTEWELL P.B. and FARMER I.W., 1976: Principles of Engineering Geology. Chapman and Hall, London, 1045 p.
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.
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.
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.
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.
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.
GILLOTT J.E., 1969: Study of the Fabric of Fine-grained Sediinents with Scanning Electron Microscope. J. Sed. Petrology. Vol. 39, pp. 90–105.
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.
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.
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.
MARTIN R.T., 1966: Quantitative Fabric of Wet Kaolinite. Clays and Clay Miner. Vol. 14, pp. 247–287.
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.
MOSELEY, H.G.J., 1913: The High Frequency Spectra of the Elements. Phil. Mag., Vol. 26, p. 1024.
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.
SORBY, H.C., 1853: On the Origin of Slaty Cleavage. Edin. New Phil. J., Vol. 55, pp. 137–148.
SPRY, A., 1969: Metamorphic Textures. Pergamon Press Ltd., Oxford, 350 p.
TSIDZI K.E.N., 1986: A quantitative Petrofabric Characterization of Metamorphic Rocks. Bull. Int. Assoc. Engng. Geol., No. 33.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tsidzi, K.E.N. Foliation index determination for fine-grained metamorphic rocks. Bulletin of the International Association of Engineering Geology 36, 81–88 (1987). https://doi.org/10.1007/BF02600942
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02600942