MESOZOIC MAGMATISM AND DEFORMATION IN THE NORTHERN WHITE MOUNTAINS, CALIFORNIA AND NEVADA

Mesozoic arc magmatism and contemporaneous deformation in the Sierra Nevada and the adjacent White Mountains have attracted substantial interest for almost a century. Despite extensive study, the lack of high-precision geochronology currently hampers our understanding of the exact interplay of magmatism and deformation. Located approximately 55 km north of Bishop, CA are three key plutons in the Northern White Mountains: the Queen Canyon hornblende diorite, the Pellisier Flats adamellite and granite, and the Boundary Peak adamellite. Field mapping of the plutons provides cross-cutting relationships between the three plutons and their associated structures. The hornblende diorite cuts the Roberts Mountain thrust fault providing a minimum age of movement, and is intruded by all other plutons and dikes. The Pellisier Flats pluton intrudes into the hornblende diorite and is pervasively sheared, possibly connected to the White Mountain Shear Zone fabric. The Boundary Peak pluton is the youngest and largely post-dates the White Mountain Shear Zone, showing only weak fabric. Hypabyssal dikes cross-cut all of the plutons and structures and are related to volcanics proximal to the Pliocene Queen Valley pull-apart structure. High-precision U-Pb zircon dating will be used to better constrain the emplacement age of the plutons and to investigate the relationship between magmatic emplacement and Mesozoic intra-arc deformation. These new data will further constrain the timing of magmatism and deformation in the northern White Mountains, and advance our understanding of the Mesozoic magmatic and structural evolution of the eastern portion of the Sierra Nevada magmatic arc.