In:
Bulletin de Minéralogie, PERSEE Program, Vol. 102, No. 2 ( 1979), p. 282-289
Abstract:
The development of the «-maximum fabric or texture commonly observed in deformed calcite rocks has been investigated by means of experimental deformation of split-cylinders of a coarse calcite marble. A new application of the split-cylinder method has been developed to enable the optical determination of the complete crystallographic rotation paths followed by individual grains during axially symmetric deformation. Optical microscope investigations of the deformed samples have revealed that the microstructures and deformation mechanisms within individual grains can be correlated with grain orientation and rotation path type. In many grains a single mechanism predominates, suggesting that the von Mises /Taylor Condition may not be fulfilled. Twinning on e is clearly an important deformation mechanism, and has an involved influence on the development of the texture. Measurement of the activity of the twinning mechanism as a function of host orientation indicates that it is linearly related to the resolved shear stress on the twin system, and that the mechanism is associated with strain heterogeneity. A number of tests have been performed to assess the homogeneity of strain in the split-cylinder experiments. The deformation has been found to be significantly heterogeneous on the grain scale. It is inferred that the relative ease of twinning in calcite at moderate homologous temperature is so great that polycrystal deformation is heterogeneous, with fewer than five glide mechanisms operating in most grains. However, the stress is relatively homogeneous, and fabric prediction models based on this premise are more applicable, when twinning is important, than those based on a homogeneous strain assumption.
Type of Medium:
Online Resource
ISSN:
0180-9210
DOI:
10.3406/bulmi.1979.7289
Language:
French
Publisher:
PERSEE Program
Publication Date:
1979
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