Short Time Heating and Cooling Experiment on Illite

Short-time heating and cooling experiment of illite was performed in the view point of frictional melting during seismic slip. Despite the classical melting experiments of clay minerals, temperatures were maintained at 800, 900, 1000, 1100, and 1200 ° C, and materials were loaded rapidly in and out of the electric furnace. The micro- to nano- meter scale observation revealed the three different processes: 1) recrystallization at 800 and 900 ° C, 2) disruption of texture at 1000 ° C, and 3) expansion and vitrification at 1100, 1200, and 1500 ° C. These results show that the rapid heating and cooling such as seismic slip would lead illite to melt in their unstable field, approximately 200 ° C higher than ordinal disruption temperature (Deer, et al. 1966). Absorbed water did not affected the result, but electrostatic aggregation of dried illite powder slightly accelerated recrystallization, disruption and vitrification. Chemical composition of molten illite shows similar composition regardless of temperature condition, lower Si and higher Al, Mg, and K content compared to the starting material. This result is completely opposite from the long-time experiment, which resulted in higher Si and lower Al, Mg, and K content. Constant Fe content before and after the short-time experiment may suggest that Fe spherules are hardly formed by rapid melting of illite.