11:15 AM - 11:30 AM
[SMP25-09] Possibility of CPO development during diffusion creep of the lower crustal minerals
Keywords:diffusion creep, CPO, lower crust, anorthite
Olivine is a major constituent minerals of the upper mantle and is known for its crystal preferred orientations (CPO), where the crystal axis is oriented in a specific direction. CPO has been thought to develop only during dislocation creep, but recently the CPO development during diffusion creep and its mechanism have been experimentally demonstrated (Miyazaki et al., 2013; Maruyama and Hiraga, 2017). However, it is not clear that the similar CPO development process occurs in minerals other than olivine.
The CPO development of plagioclase in lower crustal rocks is well known. In this study, the mechanism of CPO development during deformation of plagioclase which is responsible for the lower crustal flow was investigated by pure shear deformation experiments at high temperatures. Polycrystalline anorthite (CaAl2Si2O8), the Ca-rich end member of plagioclase, with an average grain size of ~2 µm and porosity of <0.01 vol% was synthesized using vacuum sintering technique. This polycrystalline material was placed in a carbon guide and deformed at atmospheric pressure, temperature of 1242℃ and stresses of 40~75 MPa. Microstructural analysis of the deformed samples revealed CPO development, and the stress-strain rate relationship during the deformation indicated the mechanism of diffusion creep. We discuss the possibility of CPO development during diffusion creep in the lower crust.
The CPO development of plagioclase in lower crustal rocks is well known. In this study, the mechanism of CPO development during deformation of plagioclase which is responsible for the lower crustal flow was investigated by pure shear deformation experiments at high temperatures. Polycrystalline anorthite (CaAl2Si2O8), the Ca-rich end member of plagioclase, with an average grain size of ~2 µm and porosity of <0.01 vol% was synthesized using vacuum sintering technique. This polycrystalline material was placed in a carbon guide and deformed at atmospheric pressure, temperature of 1242℃ and stresses of 40~75 MPa. Microstructural analysis of the deformed samples revealed CPO development, and the stress-strain rate relationship during the deformation indicated the mechanism of diffusion creep. We discuss the possibility of CPO development during diffusion creep in the lower crust.