Textures and Structures of Metamorphic Rocks

Abstract

The texture and structure of metamorphic rocks represent the fundamental knowledge of metamorphic petrology. This chapter describes different types of textures and microstructures under microscopy and gives clear definitions for petrogenesis of metamorphic rocks in various tectonic settings, especially in the orogenesis involving lithosphere subduction, collision, crustal thickening, and exhumation. Five types of basic textures of metamorphic rocks are described: (1) palimpsest (relict) textures, (2) crystalloblastic textures, (3) exsolution textures, (4) replacement (reaction) textures, and (5) anatectic textures. The deformation structures and mechanisms related to metamorphic rocks, mainly falling under brittle and ductile deformation categories, are also summarized. The textures and structures of metamorphic rocks can give insights into physicochemical conditions and the formation and evolution of the earth's continental crust.