Abstract
AbstractWe 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°C–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 aluminum. 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.
Highlights
Diopside, a variety of clinopyroxene is one of the major rock-forming minerals in the lower crust and upper mantle, where deformation occurs by aseismic creep
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
transmission electron microscopy (TEM) analysis confirms that our samples are melt free at 5 nm resolution (Figure A4)
Summary
A variety of clinopyroxene is one of the major rock-forming minerals in the lower crust and upper mantle, where deformation occurs by aseismic creep. Several experimental studies focused on establishing flow law of polycrystalline diopside (Bystricky & Mackwell, 2001; Dimanov & Dresen, 2005; Dimanov et al, 2007, 2003; Hier-Majumder et al, 2005) based on the equation of. Earlier experimentally determined flow law parameters of diffusion creep of polycrystalline diopside by different groups (Bystricky & Mackwell, 2001; Dimanov & Dresen, 2005; Dimanov et al, 2007, 2003; Hier-Majumder et al, 2005) show many discrepancies. There are variations in the process of sample preparation (e.g., dry or wet milling, hot-pressing conditions, chemical environment etc.) among different studies
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