The history of the intensity and orientation of a grain-shape foliation was investigated in octachloropropane deformed in simple shear at 80% of its absolute melting temperature and a shear strain-rate of 4 × 10-5 S-1. Foliation orientation, developed from the beginning of the deformation, remains steady throughout the deformation. Foliation intensity becomes steady after a bulk shear strain of about 0.9 has been accumulated. The steadiness of foliation orientation and intensity is achieved by some balance between foliation-strengthening and foliation-weakening processes. The main foliation- -strengthening process is intragranular plastic deformation. Foliation-weakening processes include dynamic recrystallization by migration of straight or or slightly wavy grain boundaries, grain dissection, rotational recrystallization, grain amalgamation, relative rigidity of hard grains and grain boundary sliding. A small but definite angle, although not constant, is observed between the foliation and the long axis of the bulk total strain ellipse. The average aspect ratio of grains is lower than that of the bulk total strain ellipse by a factor of about 0.4 at total shear strain of 1.3. The average grain size also stabilizes, becoming steady from a shear strain of 0.5 onwards. A steady grain-shape foliation may be a possible paleostress or a paleostrain-rate indicator, but cannot be a paleostrain indicator.
|Number of pages||11|
|Journal||Journal of Structural Geology|
|Publication status||Published - 1991 Dec 1|
ASJC Scopus subject areas