The acoustic emissions signature of a pressure-induced polytypic transformation in chlorite

We present results of an acoustic emissions (AE) study of single crystals of chromian-clinochlore during compression to 10 GPa at room temperature. Distinct AE are detected associated with the type Ia -> Ib transition at 6 GPa. Analysis of AE source locations and first motions at transducers are consistent with a rapid collapse of the c-axis of the sample and AE originating within the sample and not the surrounding pressure medium. This is the first time that AE have been detected directly from a phase transformation in the multi-anvil press and opens new possibilities for kinetic studies and studies of deep-seismogenesis.