High temperature simple shearing fabrics: A new experimental approach
An example is described of a shearing experiment performed on coarse-grained paradichlorobenzene at 98% of its absolute melting point. The sample is a thin sheet of material, only about seven times as thick as an ordinary petrographic thin section. It is sheared in its own plane under observation between crossed nicols, through a low-power microscope. Shear strains up to about five occur locally. An array of second-phase marker particles allows the pattern of straining in the material to be observed independently of the microstructural changes that occur. Dynamic recrystallization is seen in an original grain boundary region where the shear strain is concentrated. The new grains are mostly elongate parallel to the direction of the former grain boundary, which is also the direction of shearing. Suitably oriented new grains become filled with transverse subgrains, due to kinking or dynamic polygonization. The appearance of these intragranular features and their relation to the shearing direction recall structures and interpretations described for naturally deformed olivine rocks. It seems probable that thin sheet, analog experiments of this general type can help put kinematic interpretation of rocks deformed at high temperature on a firmer footing.
Journal of Structural Geology
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