A comparison of quartz c-axis preferred orientations in experimentally deformed aplites and quartzites

Abstract

The effect of feldspar on the development of quartz c-axis preferred orientations was investigated by experimentally deforming aplite (30% quartz) and pure quartzite under equivalent conditions and comparing the quartz c-axis patterns. Axial compression experiments were performed at temperatures of 800 and 900°C, strain rates of 10 −6 and 10 −5 s −1 , and a confining pressure of 1500 MPa. Under these conditions, both quartz and feldspar deform by dislocation creep with only minor syntectonic recrystallization. The quartz c-axis preferred orientations produced in the two rock types at equivalent deformation conditions and quartz grain strains were found to be essentially identical in pattern and strength. These results indicate that the presence of feldspar has little or no effect on the operative slip systems in adjacent quartz grains in quartzo-feldspathic rocks, and that quartz c-axis preferred orientation analyses can be performed on a wide range of crustal rock types.