Nano-texture of penetrative foliation in metamorphic rocks

Abstract

By observing four samples obtained from Jiangxi Province, China, under the scanning electron microscope (SEM), we discovered that nano-particle layers were commonly formed on sliding planes of the penetrative foliation in metamorphic rocks. We also successfully reproduced this phenomenon with a tri-axial pressure experiment. Having gone through the granulitization-alienation-partition in the shear sliding process, the nano-particles (40–95 nm in diameter) display different individual shapes and distinct layered textures. This nano-confinement layer is essentially a frictional-viscous stripe with viscous-elastic deformation. In the micro-domain stripe, activities in structural stress field-rheological physical field-geochemical field are very dynamic, corresponding to the three stages (i.e., shear sliding strengthening-weakening-exfoliating) of the foliation development in metamorphism rocks. As such, the viscous-elastic deformation behavior helps shed light on the understanding of the micro-dynamic mechanism of the structural shearing.