25 February 2012
Incipient mylonitization of a granite/granitoid, as displayed in a sample on a shelf of one of the meeting rooms adjacent to the Reading Room of the Geological Sciences building at the University of Texas at El Paso.
Same side, slightly different lighting conditions:
I’d call this a protomylonite. Some of you might prefer the term “augen orthogneiss.” No systematic asymmetry of the feldspar porphyroclasts is catching my eye on either of these surfaces, so I’m going with an off-the-cuff interpretation of pure-shear-dominated deformation. Anyone notice anything telling about this rock that reveals any deeper insights?