[S-SS30_29PM1] New perspective of great earthquakes along subduction zones

[SSS30-30] Amorphization of clay minerals by wet and dry grinding

*Koichiro FUJIMOTO¹, Rina FUKUCHI² (1.Tokyo Gakugei University, 2.Tokyo University)

Keywords:clay minerals, kaolinite, sericite, saponite, amorphous

Nanoparticles in fault zones are recently paid much attention since they give significant influences on the frictional properties (Ma et al., 2006). Nanoparticles are considered to be formed not only by mechanical grinding but also by mechanochemical processes. Amorphous nanoparticles were found in Iida-Matsukawa fault, Central Japan (Ozawa and Takizawa, 2007). It is well known that clay minerals are easily transformed into amorphous phase by mechanochemical processes. We conducted pulverization experiments of some clay minerals under both dry and wet conditions to clarify the characteristics of the pulverized materials and the mechanism of amorphization.We used kaolinite saponite and sericite as starting materials. Pulverization experiments were conducted using planetary ball mill and characterization of run products were conducted by XRD, FT-IR, TG-DTA and FE-SEM. Three minerals were completely transformed into amorphous materials by dry grinding. XRD peaks were weakened but still remain after one day wet drying as for kaolinite and sericite. On the contrary, as for saponite, XRD peaks do not show remarkable change under wet condition. Probably amorphization rate is reduced because impact energy in the ball mill is decreased in the presence of water. Presence of interlayer water affects on the behavior of saponite.