Abstract

Feldspar aggregates exhibit cataclastic flow over a wide range of conditions between low-temperature faulting and high-temperature dislocation creep; this is due to the ease of cracking on the two good cleavages and the difficulty of dislocation motion. Albite aggregates experimentally deformed at moderate to high pressures in the cataclastic flow regime are macroscopically ductile; their optical microstructures show little evidence of crushing and resemble those expected for dislocation creep. However, transmission electron microscopy (TEM) shows no dislocations or very limited dislocation mobility, but does show abundant distributed microcracks and microcrush zones that contain <0.1-µm-diameter grains. Cataclastic flow is likely to be an important deformation mechanism in nature, but it may have been overlooked because its optical microstructures have been misinterpreted and because the extreme grain size reduction facilitates transitions to other phases and deformation mechanisms.

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