Flow of synthetic, wet, partially molten "granite" under undrained conditions: An experimental study

Major problems in experimental studies of the flow of partially molten granitic (1) maintaining control of the grain size of the matrix of solid grains, (2) controlling the melt fraction, and (3) controlling the melt viscosity (closely linked to water content). To overcome these problems, we used a synthetic "granitoid" comprising a solid matrix of quartz grains (50 μm grain size) mixed with an albite-quartz melt prepared from oxides, with added water (2.5 wt %) dissolved in the melt phase (viscosity 9 × 104 Pa s). Experiments were performed undrained, with melt fractions of 0.1, 0.2, 0.25, and 0.3. Constant strain rate, creep, and stress relaxation experiments were carried out in a gas medium apparatus at 1273 and 1173 K, mostly at 300 MPa confining pressure, up to ∼15% shortening strain. Strain rates ranged between 10-4 to less than 10-7 s-1, and fully ductile mechanical behavior was observed. Melt fraction has a more profound effect on strength than water content, temperature, or total confining pressure. Low strain rate (