Hypothesis to Explain the Preferred Orientations of Quartz and Calcite Produced During Syntectonic Recrystallization
The hypothesis presented in this paper explains the preferred orientations of quartz and calcite produced during Syntectonic recrystallization, in terms of the preferential growth of grains that are stable with respect to the translation mechanisms operative in particular stress fields. The common preferred orientations of quartz and calcite, including "ac" girdles, cross-girdles, and the common maxima positions of quartz, can be correlated with predictions made by an analysis of stable growth orientations in various stress fields. Experimentally produced preferred orientations and two examples of natural quartz fabrics are used to illustrate the hypothesis. One of these, a mylonite from New Zealand, is treated in detail. It is shown that the mylonite results from simple flattening, and not from translational movements.