Monomineralic mobilization of plagioclase by shock: an experimental study

Shock recovery experiments of plagioclase feldspar in contact with pyroxene, shock-loaded at 36-53 GPa, showed that monomineralic glass of plagioclase was mixed with brecciated pyroxenes with virtual absence of mixed-mineral melts. This amorphous phase of plagioclase produced at 36-42 GPa displays enormously high ductility although the amorphous phase is less likely to be a quenched high-pressure melt because both shock and post-shock bulk temperature cannot exceed the melting point. The results suggest that alkaline components in feldspar can be extensively mobilized even in a very short duration of shock, which can never be achieved by normal diffusion in the same time scale. Since feldspar is a major carrier phase of alkaline volatiles. shock mobilization mechanism may explain shock disturbance of Rb-Sr and Ar-39-Ar-40 ages of basaltic shergottites. (C) 2000 Elsevier Science B.V. All rights reserved.