Semi-brittle behavior of olivine aggregates revisited

Triaxial deformation experiments on olivine aggregates were conducted at pressures of 1.3–3.4 GPa and temperatures of 670–1160 K under nominally dry and water-saturated conditions. The maximum strength of olivine was found to be well described by a reported flow law for dry olivine controlled by Peierls creep. Vigorous acoustic activity followed by faulting was recorded in the olivine samples deformed to a maximum stress of ∼2 GPa at 1070–1160 K. In contrast, acoustic emissions were less active and faulting was absent at lower temperatures (670–950 K) even though the maximum stress exceeded 2.5 GPa in these runs. Our observations suggest that processes that promote microcracking (e.g. kinking and microfaulting), rather than elevated stress magnitude, are necessary for the occurrence of faulting.