Direct shear of olivine single crystals

Stress evolution and associated microstructure during transient creep of olivine at 1000–1200 °C

“…• Deformation at 1200 °C is in good agreement with Keefner et al (2011), Tielke et al (2016 (001)) and Hirth and Kohlstedt (2003).…”

“…The stress surpasses steady state estimations from the single crystal flow laws from Evans & Götze (1979) and Demouchy et al (2013), but is in good agreement with the flow law based only on [001](100) glide from deformation experiments in shear from Tielke et al (2016), as seen in Figure 12. The higher strength of our samples can at least partly be attributed to the lack of sufficient independent slip systems in polycrystalline olivine samples (the so called olivine paradox) and the difference between single crystal and polycrystal rheology (e.g., Evans and Goetze, 1979, their Fig 14).…”

“…Experiments performed at temperatures relevant to the uppermost lithospheric mantle (≤ 1000 °C, e.g. Raterron et al, 2004;Demouchy et al 2009Demouchy et al , 2013Demouchy et al , 2014Mei et al, 2010;Idrissi et al, 2016;Tielke et al, 2016) report a lower strength of olivine than was expected from extrapolation of high-temperature flow laws. The low temperature plasticity is a key to understanding deformation of the shallow upper mantle (Hirth & Kohlstedt, 1995) but also in subducting slabs Kirby, 1980;, where it governs the stress storage capacity and therefore the maximal stress release of deep earthquakes (e.g., Proietti, 2016).…”

“…The dominant deformation mechanism depends on the stress, temperature, grain size, strain rate, the crystal chemistry, the oxygen fugacity, partial melt content and even the trace amount of hydrogen (e.g. Carter & Lallemand, 1970;Chopra & Paterson, 1981Mackwell et al, 1985;Cooper & Kohlstedt, 1984, 1986Bai et al, 1991;Bai & Kohlstedt, 1992;Mei & Kohlstedt, 2000 a,b;Hirth & Kohlstedt, 1995, 2003Warren & Hirth, 2006;Mackwell, 2008;Faul et al, 2011Faul et al, , 2016Keefner et al, 2011;Demouchy et al, 2012;Tielke et al, 2016Tielke et al, , 2017. Dislocation glide is thought to be the dominant deformation mechanism at low temperatures (< 1200 °C in Fo 90 ) and for grain sizes > 1 mm prevalent in mantle olivine, since Si is the slowest diffusing species in silicates and its diffusivity is highly dependent on temperature (Chakraborty, 2010).…”

Hydrolytic weakening in olivine single crystals

“…At low stress (≤100 MPa) and high temperature (≥1200°C) conditions, strain rate followed a power law dependence on stress. At high stress (≥100 MPa) and low temperature (≤1100°C) conditions, strain rate was more stress sensitive than at low stress and high temperature conditions, suggestive of an exponential dependence upon stress [ Tielke et al , ].…”