Petrographic and Geochronologic Analysis of the Albany Granite of the Medicine Bow Mountains, Southeast Wyoming

The Albany Granite pluton is one of several similar-looking bodies of granite in southeastern Wyoming, classified simply as pink massive granites. Because of their similar petrology these granites were all assumed to be correlative with the 1.4 Ga Sherman Granite in the Laramie Mountains. However, a recent study dated the Albany Granite at ~1.75 Ga. This result called into question the simplicity of the intrusive system in the area, deformation of the Albany Granite by the Cheyenne belt shear system, and the relationship of the Albany Granite to its wall rock. These questions will be answered in this study through field work, sample collection, rock preparation, modal analysis, geochemical analysis, petrography, and radiometric dating. We hypothesize that the dated 1.75 Ga rock is actually wall rock to the Albany Granite; the age of the Albany Granite is ~1.4 Ga; signs of solid state deformation in thin-sections is due to a source of deformation other than the Cheyenne belt; and that the contact between Albany Granite and the wall rock interfingers. Alternatively, if the Albany Granite is 1.75 Ga, signs of solid state deformation could be attributable to the Cheyenne belt. Work has been ongoing since July 2009 and will continue over the next year.