Frictional sliding in serpentine at very high pressure

Using a new four-channel system for detecting acoustic emissions in a multianvil apparatus, we have assessed the press it re-tempera tu re range for such emissions, as well as the role of dehydration, by deforming samples of extensively serpentinized peridotite. We show that in the absence of dehydration and for Samples initially faulted at low pressure, acoustic emissions occurred well outside the expected pressure-temperature field of unassisted brittle failure. Emissions were also detected during and after dehydration of serpentine. Microstructures of post-run specimens revealed fault Slip with offsets up to similar to 500 mu m, regardless of whether or not dehydration took place. Dehydration appears to effectively stop slip on preexisting faults and create new ones. Analysis of P-wave travel times from the four sensors confirmed that the acoustic emissions originated within the specimen during fault slip. These observations suggest that earthquakes can be triggered by slip along all existing fault containing serpentine under significantly higher pressure and temperature conditions than previously thought possible without dehydration. (C) 2008 Elsevier B.V. All rights reserved.