VOLUME LOSS AND TECTONIC FLATTENING STRAIN IN GRANITIC MYLONITES FROMTHE BLUE RIDGE PROVINCE, CENTRAL APPALACHIANS

Granitic mylonites from the Blue Ridge province in the central Appalac hians demonstrate the contribution of various deformation mechanisms t o the strain geometry that developed during greenschist facies deforma tion in thrust-related shear zones. Strain accumulated through catacla sis in feldspar, crystal plastic processes in quartz, and a significan t contribution of pressure solution in both feldspar and quartz. Strai n analysis was performed using R(f)/phi(f) techniques on quartz grain shapes and by measuring stretched and boudinaged feldspars, Petrograph ic and geochemical evidence indicates that deformation ranged from iso volumetric to upwards of 60% bulk-rock volume loss. Quartz and feldspa r strain values plot within the field of apparent flattening. Feldspar s in both XZ and YZ sections are boudinaged and separated by transvers e veins and record a true tectonic flattening strain. Strain data indi cate that the bulk deformation path in shear zones throughout the Blue Ridge province significantly deviated from plane strain.