Mylonitization of the Wanapitei Quartzite, Sudbury, Ontario

Abstract

<p>Mylonitized Wanapitei quartzite (Huronian-aged), was examined in detail at two occurrences along the Grenville front near Sudbury, Ontario.</p> <p>In the Coniston study area, the rocks show an increase in mylonitization from crush breccia to ultramylonite as the Wanapitei fault is approached.</p> <p>The prevalence of optically observed features such as undulatory extinction, subgrain development and deformation lamellae increases with the mylonitization. The occurrence of these features can be explained in terms of dislocation movements within the quartz crystal lattice.</p> <p>The mylonites were produced by pure shear or simple shear since on the deformation plot the samples lie between constriction-type deformation and flattening-type deformation with a k = 0.985.</p> <p>Dislocation climb and glide were the dominant deformation mechanisms operating in these rocks. However, as the grain size is reduced Nabarro-Herring creep may have become a dominant mechanism of the matrix of the mylonites.</p>