Growth and deformation mechanisms of talc along a natural fault: a micro/nanostructural investigation

This paper documents the occurrence of large amounts of talc within a continental normal fault. The talc-in reaction is deformation-enhanced and occurs by the interaction between dolostones and silica-rich hydrothermal fluids. In the high-strain, foliated fault core, talc forms an interconnected network of oriented (001) lamellae, 200–300 nm thick, locally associated with minor tremolite fibres, up to 300 nm in diameter. The talc structure is affected by several strain-induced defects, among which (001) interlayer delamination that produces talc ‘‘sublamellae’’ down to 10–30 nm thick. Micro/nanostructural observations definitely point to a predominant deformation mechanism of (001) frictional sliding, further enhanced by pervasive delamination that gives rise to an almost infinite number of possible sliding surfaces. These effects have fundamental implications in fault mechanics, resulting in significant fault weakening