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A Study of Quartz Orientation and its Relation to Movement in Shear Folds

Published online by Cambridge University Press:  01 May 2009

P. K. Gangopadhyay  and
M. R. W. Johnson
P. K. Gangopadhyay
Affiliation:
Grant Institute of Geology, Edinburgh.
M. R. W. Johnson
Affiliation:
Grant Institute of Geology, Edinburgh.
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Abstract

The orientation of quartz in small shear folds, which belong to two movement episodes, is considered to result from laminar flow along the axial plane surfaces. The locations of fabric maxima and girdles are controlled by the orientation of the a–kinematic axis, which in shear folds may not be normal to the fold axis, and the shear surfaces. The earlier fabric consists, essentially, of paired maxima arranged systematically about the axial plane; ac–girdles are absent. The explanation of the near-orthorhombic symmetry of the first fabric in terms of a late “flattening” overprinted upon the previously-formed fold is not favoured: quartz orientation developed during the first folding. The later fabric results from the recrystallization of quartz grains with their largest dimensions and c–axes parallel to the calculated a–kinematic axis of second folding.

Type
Articles
Information
Geological Magazine , Volume 99 , Issue 1 , February 1962 , pp. 69 - 84
Copyright
Copyright © Cambridge University Press 1962

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References

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