TWO-DIMENSIONAL ORIENTATION OF FINE QUARTZ GRAIN SUBJECTED TO DIRECT SHEAR

抄録

The degree of grain orientation given by the magnitude of vector strength by visual measurements is compared with that of the birefringence ratio by an indirect one. To link both expressions, a concentration degree of distribution is introduced on the assumption that the grain arrangement obeys the circular normal distribution. The longitudinal section illustrating the shear-induced fabrics is put under a polarizing microscope, and quartz grains in it are measured by the trigonometric treatment. The grain orientation brought forth during shearing is evaluated as a random orientation, because grains rotate as the horizontal displacement increases. However, it is also shown that the parallel grain arrangement exists in a certain direction such as the slip line and its conjugate at the top of crack occurring during shearing.