Seismic properties of subducting oceanic crust: Constraints from natural lawsonite-bearing blueschist and eclogite in Sivrihisar Massif, Turkey

Lattice Preferred Orientation and Deformation Microstructures of Glaucophane and Epidote in Experimentally Deformed Epidote Blueschist at High Pressure

“…For deformed samples under a high shear strain (γ > 2), type-2 LPOs of glaucophane exhibited the [100] axes subnormally aligned with the shear plane and the [001] axes in subparallel alignment the shear direction (Figure 5g-k), which have been reported in many natural blueschists [15][16][17][18][28][29][30][31][32]. This type-2 LPO of glaucophane is also similar to the type-1 LPO of hornblende [43,44].…”

“…However, subducting oceanic crust is also a potential anisotropic layer where many elastically anisotropic minerals are stable [3,12]. Therefore, recent studies have suggested that type-2 LPO of glaucophane may affect the trench-parallel seismic anisotropy of the forearc region, where the subducting slab has a high dip angle [15][16][17][18]. This is because the propagation velocity of the fast S-wave (Vs1) through the b-and c-axes of the glaucophane is much faster than that through an a-axis in glaucophane.…”

“…Other studies have reported that the tremors and low-frequency earthquakes (LFEs) occur near the top of the low-velocity layers [13,14]. In addition, researchers have suggested that the lattice preferred orientation (LPO) of glaucophane, one of the elastically anisotropic minerals in blueschist, may affect the trench-parallel seismic anisotropy of the forearc region where the subducting slab has a high dip angle [15][16][17][18].…”

“…Several dislocation slip systems of glaucophane were first reported by a transmission electron microscopy (TEM)/high-resolution electron microscopy (HREM) study [21]. Recent studies on natural blueschists have reported three types of LPOs for glaucophane; (1) LPO indicating a (100)[001] slip system (or, point/SL-type LPO) [15][16][17][18][28][29][30][31][32], (2) LPO indicating a {110}[001] slip system (or, girdle/L-type LPO) [15,16,18,28,31], and (3) LPO indicating a (010)[001] slip system [33]. Although there has been little description on the slip systems of epidote, certain TEM/HREM studies have suggested the easiest slip plane (e.g., [24,34]).…”

Erratum to: Crystal preferred orientations of olivine, orthopyroxene, serpentine, chlorite, and amphibole, and implications for seismic anisotropy in subduction zones: a review

“…There are some previous reports on the study of CPO and resultant seismic anisotropy of glaucophane Kim et al, 2013;Cao and Jung, 2016;Ha et al, 2018), lawsonite (Kim et al, 2013(Kim et al, , 2016Cao et al, 2014;Cao and Jung, 2016), and epidote (Cao et al, 2011Ha et al, 2018). However, these data are very limited so far and more detail studies on the development of CPOs of those minerals and resultant seismic signatures are needed to better understand the seismic anisotropy in the subducting slabs.…”