GEOSPATIAL AND PETROGRAPHIC ANALYSIS OF LEUCOGRANITE IN THE BEAVER DAM MOUNTAINS, SOUTHWEST UTAH

The presence of leucogranite outcrops in the Western United States suggest possible locations of suture zones for Precambrian terranes accreted to Laurentia. While large scale maps exist, little has been done to extend the suture zones at a fine scale, between Proterozoic terranes such as the Mojave and Yavapai Provinces. Outcrops of Proterozoic leucogranite in the Beaver Dam Mountains of Southwest Utah and the Virgin Mountains of Northwest Arizona indicate possible locations of these suture zones. Using GIS and GPS equipment the locations of leucogranite outcrops following a North-South trend, up to one kilometer in length have been identified near the Utah/Arizona/Nevada border. After field verification these rocks have been correlated to Precambrian basement rocks such as the Grand Canyon Metamorphic Suite to the southeast.

Petrographic analysis confirms the presence of high amounts of leucocratic minerals such as orthoclase and quartz as well as garnet indicate a high pressure origin and possible partial melting. Garnet located near the contact with the gneiss and schist host is evidence that minerals from the parent rock may have been consumed and incorporated into the leucogranite by peritectic reactions.