High-temperature mechanical properties of basalt

The concept of an incremental and cyclic thermal-stress-induced fracture mechanism in subsolidus cooling basalt is introduced. Observations of striations on the fracture surface permit a coupled model of fracture lance formation and polygon kinematics during the cyclic advances of a cracking front. The dynamic Young's modulus and the dynamic shear modulus of olivine tholeiite were measured to 865 C and 800 C respectively. Thermal expansion correction factors were determined as a function of temperature for the same olivine tholeiite. A marked change in slope at 998 K suggests that grain boundary relaxation and sliding occur. This suggests that viscous flow processes in intercrystalline glass at the glass transition itself are the crack tip blunting, striation producing mechanisms, and that advancing cracks stop and generate striations when they kinetically pierce the T sub g interval.