DEFORMATION-ENHANCED FLUID DISTRIBUTION IN FELDSPAR AGGREGATES AND IMPLICATIONS FOR DUCTILE SHEAR ZONES

Experiments at 900 degrees C and 1.4 GPa show that the distribution of aqueous fluid in fine-grained feldspar aggregates changes from isolat ed pores under hydrostatic conditions to mostly wetted grain boundarie s during deformation; the isolated pore distribution is rapidly regain ed during annealing following deformation. The deformation-enhanced fl uid distribution causes a snitch from dislocation creep to diffusion c reep accompanied by a significant decrease in strength; it also increa ses the bulk transport rate through the aggregate by more than an orde r of magnitude. A change in fluid distribution is not observed in fine -grained quartz aggregates deformed at similar conditions. If deformat ion-enhanced fluid distribution occurs in naturally deformed feldspath ic rocks, it could help to explain the localization of strain and enha ncement of bulk transport in ductile shear zones.