Recognising the crystallographic signature of recrystallisation processes in deformed rocks: a study of experimentally deformed rocksalt

The microstructural development of synthetic rocksalt experimentally deform ed at 100-200 degreesC can be dominated either by grain boundary migration recrystallisation or by subgrain rotation recrystallisation, depending on w ater content. Samples taken from both regimes have been analysed using auto mated electron backscatter diffraction in order to collect crystallographic orientation and misorientation data. The frequency distribution of boundar y misorientations, the boundary hierarchy characteristics and the nature of any crystallographic preferred orientation (CPO) have been used to determi ne the crystallographic signature of both recrystallisation processes. Domi nant subgrain rotation recrystallisation results in many low to medium angl e (4-20 degrees) boundaries, a strong CPO and a continuous boundary hierarc hy. Dominant grain boundary migration recrystallisation results in few low or medium angle boundaries, and a discrete boundary hierarchy. The causes o f these differences and the potential application of crystallographic signa tures to the study of naturally deformed rocks are discussed. (C) 2000 Else vier Science Ltd. All rights reserved.