Change of deformation mechanisms during low temperature flow of rocks — observation from micron to nanometer scales

Abstract

Recent studies on nano-materials in materials science revealed that nanomaterials may have fantastic features due mainly to size-effect of the materials. For example, nano ceramics may have very high ductility at room temperatures and pressures, even though normal ceramics is easily deformed by brittle fracturing. What and how much do we know about the nature of nano or nano to micron scale geological materials? What factors contribute to their occurrence? How do they flow at geological conditions and how do they affect the rheology of rocks? Upper crustal deformation is characterized by low temperature flow of rocks under unsteady state, which results in progressive grainsize reduction and leads to the occurrence of micron to nano meter scale materials in fault zones. The examples of naturallydeformed upper crustal rocks presented in the paper help to unravel the importance of nano to micron scale rock materials during the low temperature flow of rocks.