Microstructure and Paleopiezometric Constraints on Deformation Conditions of Olivine From the Southern Appalachian Buck Creek Ultramafic Complex

Abstract

Microstructural and paleopiezometric analyses help constrain conditions and mechanisms of deformation of the Buck Creek ultramafic complex in southwestern North Carolina. Previous work has determined that the complex is an emplaced fragment of partially subducted ocean crust that experienced anhydrous prograde metamorphic conditions to about 800˚C and 1.0 GPa. Twelve olivine-rich dunite/troctolite samples from the Buck Creek ultramafic complex are the focus of this study. Previous work with electron backscatter diffraction (EBSD) shows that the olivine crystallographic preferred orientation (CPO) patterns are generally consistent with axial-[100] or D-type fabric formed under moderate to high stresses with low water content. Axial fabrics may also result from non-plane strain conditions (e.g. constriction or flattening).