Go Back Forwrd Homepage



The term mylonite was introduced by Lapworth in 1885 to describe rocks that appeared along the Moine Thrust in Scotland. Lapworth envisaged that these rocks had been produced by strong grinding or milling of the Moine schists: hence the term mylonite from the Greek mylon- a mill. He considered these rocks to have been formed solely by crushing with no concurrent recrystallization. In the formation of these rocks a strong layering or banding had developed. To Lapworth then the important features of a mylonite were that it had been produced solely by cataclasis without any associated recrystallization of the constituent particles and that a well-developed layering had formed. The terminology of mylonites is discussed at length by Christie (1960) who points out that recrystallization is commonly very widespread in the Moine mylonites. However, he considered that recrystallization postdated the deformation. It is important to note that most of the classic microstructures described by older workers and interpreted by them as cataclastic structures are due to recrystallization. Such microstructures particularly include the classical mortar structure in which an aggregate of fine-grained, new recrystallized material is developed around the margins of older deformed grains