mylonitized

Mylonitized refers to rock that has undergone mylonitization, a process of ductile deformation occurring at elevated temperatures and pressures deep within the Earth's crust. This deformation results in a significant recrystallization and grain size reduction, creating a fine-grained, foliated rock texture. The original rock, whether igneous, sedimentary, or metamorphic, is transformed into a mylonite.

Key characteristics of mylonitized rocks include the development of a strong foliation, which is a planar arrangement of mineral grains. This foliation is often accompanied by a lineation, a linear fabric within the rock. The minerals within a mylonite are typically flattened, elongated, and recrystallized into smaller grains. Common minerals found in mylonites include quartz, feldspar, and mica.

Mylonitization typically occurs along major fault zones, such as thrust faults and strike-slip faults, where large-scale shear movements take place. These zones are often referred to as mylonite belts or shear zones. The orientation of the foliation and lineation can provide important information about the direction and sense of the shear movement during the mylonitization process. Studying mylonitized rocks is crucial for understanding the tectonic history and deformation mechanisms of the Earth's crust.