Читать книгу Mantle Convection and Surface Expressions - Группа авторов - Страница 38

Most deformation experiments have focused on slip systems and texture development in lower mantle phase (Immoor et al., 2018; Merkel et al., 2007; Miyagi et al., 2010; Miyagi & Wenk, 2016), and only a few experiments have studied rheological properties (e.g., Girard et al., 2016). This is largely due to experimental difficulties related to measurement of rheological properties under controlled strain rate conditions and also due to intense interest in the relationship between texture and anisotropy in the lower mantle. Texture measurements have largely been performed at uncontrolled strain rates and in most cases at room temperature in the DAC. In contrast, measurements of rheological properties require precise control of strain rates and temperature in order to access and characterize stress–strain rate relationships for various deformation regimes. Most deformation experiments have been performed in the dislocation glide regime or in dislocation creep regime with no experimental studies on diffusion creep at lower mantle pressures and temperatures. Typically, diffusion creep rheology has been estimated based on measured or calculated diffusion coefficients and estimates of mantle grain size combined with the diffusion creep equation (e.g., Ammann et al., 2010; Deng & Lee, 2017; Van Orman et al., 2003; J. Xu et al., 2011; Yamazaki et al., 2000; Yamazaki & Karato, 2001b). A few diffusion creep studies have been performed on lower mantle analog materials (Karato et al., 1995).

The following discussion primarily focuses on experimental studies that achieve pressures in excess of ~20 GPa. These measurements were performed either in the dislocation glide or in dislocation creep regime. In the following sections, I will first discuss studies on mineral strengths and then will discuss texture measurements and slip system activities.