11:15 AM - 11:30 AM
[SCG46-18] Frictional characteristics on antigorite serpentine at the condition of subduction zone
Keywords:subduction zone, fault, antigorite, frictional characteristics
Seismic tomography and metamorphic petrology illuminate that antigorite serpentine is a dominant phase in mantle wedge through interactions with fluids released from the subducting oceanic slab (Matsubara et al., 2009; Obara et al., 2011; Yamasaki and Seno, 2003). Since a wide spectrum of slip behavior is reported in the subduction plate boundary where serpentinite may exist, it is important to understand its frictional characteristics at the condition of the subduction zone. Here, we conducted friction experiments on antigorite serpentinite (Corsica, France) cores using a Griggs-type apparatus, installed at Tohoku University. All experiments were conducted at various confining pressures from 500 to 1500 MPa with temperatures of 500 ℃, and shear displacement rates of 0.14–1.4 μm/s. To investigate the frictional characteristics, the samples were pre-cut at 45° to the long axis of cores to induce sliding on these pre-cut surfaces. The frictional strength of samples was less than 400 MPa, corresponding to a coefficient of friction of 0.1–0.2. The samples also show stable sliding with velocity-strengthening behavior. Microstructural observations show that sliding surfaces were smoother compared with the starting material and were covered with fine-grained antigorite less than 1 μm in diameter. Raman spectra also show that there is no evidence of dehydration. The frictional strength of antigorite serpentinite obtained in this study was lower compared with previous experiments conducted under similar conditions using powdered samples (e.g., Proctor and Hirth, 2016). The frictional characteristics of serpentinite illuminated by the present study may influence the fault dynamics including slow slip events of the plate boundary near the mantle wedge.