In a quartz-feldspar mylonite specimen from the Darling fault zone, Western Australia, the quartz c-axis fabrics were analyzed using a combination of the conventional universal-stage methods and the photometric method of determining fabric variations. Previously existing techniques for gauging fabric homogeneity proved laborious; therefore, detailed analysis was performed using the photometric approach. The results were considered in relation to grain morphological characteristics, and three types of quartz grains were recognized. Domains of each of these types of grains exhibited different c-axis fabrics. Spatial distribution of fabric parameters determined from the photometric data revealed the degree and nature of fabric heterogeneity. It is suggested that these variations in fabric are the result of variable strain produced by the action of a uniform stress on a layered material in which alternate layers have different rheological properties related to the proportion of quartz and feldspar.

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