LATE CRETACEOUS MAGMATISM WITHIN THE NORTH EAST MOJAVE REGION : NEW GEOLOGIC MAPPING, GEOCHEMISTRY AND U/PB IN ZIRCON ANALYSIS OF TEUTONIA BATHOLITH UNITS LOCATED WITHIN THE MID HILLS QUADRANGLE, EAST MOJAVE NATIONAL SCENIC AREA

At approximately 80 Ma a significant tectonic shift occurred on the western margin of North America. Magmatism and deformation within the Mesozoic magmatic arc ceased and migrated over 1000km inland. This shift has been largely attributed to a shallow slab section within the subducting Farallon oceanic plate. This shallow slab section is thought to be caused by the subduction of two aseismic oceanic terrains (Hess and Shatsky orogenic plateau) at approximately 90 Ma.

The Teutonia Batholith, originally described by Beckerman et al. 1982 is a Cretaceous metaluminous to weakly peraluminous unit located within the Northeastern portion of the East Mojave National Scenic Area (EMNSA). The batholith presents a unique opportunity to study magmatism that occurred during the supposed passage of a segmented flat slab beneath the Mojave region.

This study presents new geologic mapping, geochemistry and U/Pb in zircon analysis for units of the Teutonia Batholith, within the Mid Hills Quadrangle, (EMNSA). The purpose of this study is to gain a better understanding of the magmatism that occurred during the Sevier Laramide transition within the Mojave.

Teutonia units within the map area include the Mid Hills Monzogranite, Rock Springs Monzodiorite, and Black Canyon Horneblende Gabbro. A new map produced in ArcGIS shows updated contacts between batholith units and feeder dikes, as well as locations and orientations of faults within the area. Syn-magmatic stress indicators show distinct regional stress orientations during the time of emplacement, that differ for the North and South of the map area, due to fault movement.

Field observations and U/Pb in zircon analysis of the Mid Hills monzogranite show it can be subdivided into two distinct units. The proposed Wild Horse Canyon subunit distinguishes itself by containing potassium feldspar megacrysts up to 80 cm in length, while the Round Valley subunit distinguishes itself by lacking megacrysts and containing pervasive elongate mafic enclaves. New U/Pb in Zircon analyses by this study show the units distinguish themselves in age as well. New LA-ICP-MS ages for the Wild Horse Canyon and Round Valley subunits will be presented.