EXPERIMENTAL DISSOLUTION-PRECIPITATION CREEP IN QUARTZ AGGREGATES AT HIGH-TEMPERATURES

Rapid compaction creep has been achieved in fine-grained quartz aggregates during hydrothermal isostatic pressing (HTIP) at 1200K, a confining pressure of 300MPa and a pore water pressure of 200 MPa. While raising the pressure and temperature over a period of three hours, the porosity decreased by over 50%. During subsequent HTIP for periods up to 4 hours, further porosity reduction occurred at compaction creep rates between 10(-5) and 10(-6) s-1. Changes in grain shapes, grainsize distribution, pore geometry and microstructures on grain surfaces, together with an absence of substantial brittle or intragranular plastic deformation, indicate that compaction creep has occurred largely by dissolution-precipitation processes. Interpenetration of grains and grain-shape truncation are well-developed at grain contacts. Arrays of fine-scale ridges, plateaus and flat-bottomed pores on interfaces indicate that the fluid distribution on actively dissolving interfaces is a dynamic structure that is not controlled entirely by equilibrium wetting angles.