ABSTRACT
A series of high-velocity frictional experiments on monzodiorite and granite at high velocities (to 13 m/sec), large displacements (97–1433 m) and low normal stresses (to 1.5 MPa) are conducted to measure the temperature rise and friction along simulated faults. Temperature rise is measured with PR and CA thermocouples and with a radiation thermometer. Measured average temperature along simulated faults during frictional melting reaches about 1070–1190 °C for monzodiorite and 1130–1145 °C for granite, well above the decomposition temperature of biotite (650 °C). This temperature is consistent with an almost complete lack of biotite clasts in experimentally produced pseudotachylyte.Thus the frictional melting is a selective melting process. Measured temperature in monzodiorite specimens agrees with calculated temperature distribution by use of the finite element method.
Initial strength peak in friction is followed by a gradual decay in friction with increasing displacement upon the initiation of experiment Friction, however, begins to increase as the fault is heated, undergoes a broad peak and eventually approaches a steady-state. The moment when the simulated fault attains steady-state temperature distribution corresponds to the moment when the fault surface reaches steady-state mechanically. Visible frictional melting begins to occur near the second broad peak in friction, hence well before the steady-state temperature distribution is attained.
