Origin and geological significance of mylonitic shear zones, northern Lucy Gray Range, Clark County, Nevada

Clinton H Christensen, University of Nevada, Las Vegas


The Beer Bottle Pass pluton, at the northern end of the Lucy Gray Range, Nevada, is part of a continent-scale belt of 1.4 Ga intrusive rocks that extend from California to Labrador. These granites are conventionally interpreted as anorogenic; however, recent work has documented that some of these plutons may have been deformed during or after emplacement. In the Lucy Gray Range, a series of mylonite zones is spatially associated with the Beer Bottle Pass pluton. An integrated study involving field and laboratory work, was used to distinguish between three possible scenarios for the origin of the mylonites: (1) intrusion into an active shear zone, (2) post-emplacement ductile deformation, and (3) mylonitization during and as a consequence of forcible pluton emplacement. Observations made during this study indicate that forcible intrusion is unlikely and the mylonites are a result of late synkinematic or post emplacement deformation.