Diffusion creep of diopside

Subhajit Ghosh(Institut des Sciences de la Terre d’Orléans), Sanae Koizumi, Takehiko Hiraga
Journal of Geophysical Research: Solid Earth, https://doi.org/10.1029/2020JB019855

We have conducted uniaxial compression experiments on fine‐grained diopside with either 4 or 10 vol% forsterite and 10 vol% anorthite. We changed the average grain size in the diopside with forsterite aggregate from 0.43 to 4.07 μm to reveal the grain size sensitivity of the creep rate. Mechanical data were obtained at a stepped load for a temperature range of 1050 to 1170°C. The observed strain rates are best explained by stress and grain size exponent values of 1 and 2, respectively, and activation energy of ∼720 kJ/mol, which indicates lattice diffusion creep. Anorthite bearing aggregate is ∼3 times weaker than forsterite‐bearing aggregate, probably due to the presence of aluminium. We have compared previously reported diffusion creep rates of diopside in nondimensional stress and strain‐rate space, constructed based on our diffusion creep law. It demonstrates that all the earlier mechanical data are well summarized by our diffusion creep flow law.

Arrhenius plot of strain rate as a function of 10000/T of dry diopside (this study), Fe‐olivine (Yabe & Hiraga, 2020; Yabe et al., 2020) (Y), Fe‐free olivine (Nakakoji et al., 2018) (N), enstatite (Bruijn & Skemer, 2014) (B&S), and anorthite (Rybacki & Dresen, 2000) (R&D) in the diffusion creep regime are shown. All the plots are fixed to d = 10 μm and urn:x-wiley:21699313:media:jgrb54624:jgrb54624-math-0092 = 30 MPa.