Compressive strength data for pure plagioclase and pure epidote aggregates deformed at high-pressure, high-temperature conditions

We experimentally investigated the relative strength of pure epidote and pure plagioclase aggregates at a confining pressure of 1 GPa, two different temperatures (550 and 650 °C) and two different strain rates (5.10^-5 and 5.10^-6 s^-1) using a Griggs apparatus.

Furthermore, we investigated potential strength differences due to differences in grain size by deforming aggregates with grain-size ranges of either 90-135 μm or <25 μm. The chemical composition of the starting material is 64 % anorthite, 35 % albite, and 1 % orthoclase for plagioclase, and 69 % epidote. During deformation, most aggregates underwent buckling, i.e., the top part of the sample was sheared relative to its bottom part, which had a strong influence on the mechanical data.