An experimental investigation of the interactions between reaction-driven and stress-driven melt segregation: 2. Disaggregation at high melt fraction

Abstract

To investigate the coupling between stress-driven melt segregation and reaction-driven melt infiltration, we performed static annealing and torsional deformation experiments on couples constructed from a melt-rich basaltic source and melt-poor olivine + orthopyroxene + chromite + basalt sink. In this study (the second of two companion papers), the melt source is almost completely molten with $\phi$ = 0.8–0.9, well above the rheologically critical melt fraction. We deformed two geometries of source/sink couples with the source either as the core or the outer ring of a cylinder. Our experiments demonstrate (1) that deformation significantly enhances the rate of melt infiltration from the source into the sink and (2) that combined reaction and deformation promote greater strain localization than does deformation alone. Deformation and melt infiltration enhance disaggregation at the interface of the source and sink. The implication of these coupled interactions is that deformation and melt-rock reaction may enhance the corrosion (or ‘stoping’) rates of the wall rocks of magma chambers and intrusions in the crust and upper mantle.