In interpreting metamorphic rocks, porosity is one of the textural elements which petrologists have largely ignored, even though mineral aggregate porosity textures can reveal important clues concerning the identity and interconnectivity of the metamorphic pore fluids. The geometry of the mineral grain boundaries in natural rocks will be observed. A series of experiments will also be run that will metamorphose rocks. These experimentally-metamorphosed rocks will be analyzed for total porosity, porosity distribution, and dihedral angle geometry using TEM, SEM and BSEM. Measured dehedral angles will be correlated for differnet fluid chemistries and run durations and compared to those for the naturally-metamorphosed samples. In samples treated at low temperatures with H2O-NaCl, H2O-CaCl2 or H2O-FeCl3, the electron microprobe will be used to measure the Na, Ca, Fe and Cl distributions across the samples to document ionic, and hence, fluid, transport rates into the samples. These measurements will reveal whether fluids of different chemical composition will infiltrate rocks and form interconnected networks of fluid-permeated channels at metamorphic conditions. Such experiments will have significant implications for the interpretation of metamorphosing crustal regions and the potential for fine scale fluid percolation through metamorphic terrains.
