Tectonites are

metamorphic Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

or tectonically deformed rocks whose fabric reflects the history of their deformation, or rocks with

fabric Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not ...

that clearly displays coordinated geometric features that indicate continuous solid (ductile) flow during formation. ''Planar foliation'' results from a parallel orientation of platey mineral phases such as the

phyllosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

s or

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...

. Slender prismatic crystals such as

amphibole Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is A ...

produce a ''lineation'' in which these prisms or columnar crystals become aligned.Best, Myron G., ''Igneous and Metamorphic Petrology'', Wiley-Blackwell, 2nd ed. 2002, p. 448 Tectonites are rocks with minerals that have been affected by natural forces of the earth, which allowed their orientations to change. This usually includes recrystallization of minerals, and the foliation formation. Tectonites are studied through structural analysis and allows for the determination of two things: *The orientation of shearing and compressive stresses during (dynamic) metamorphism *The later (or final) stages of metamorphism According to the nature of mineral orientation, there are three main groups of tectonites, L-Tectonites, S-Tectonites, and LS-Tectonites. The different types reflect on the different ways that matter moves. *L-Tectonites are aligned in a linear fabric, which allows the rock to split into rod-like shapes due to the two intersecting planes. The foliation of this type is not strong. *S-Tectonites are the fabric that is dominantly a foliation fabric which allows the rock to split into plate-like sheets that are parallel to foliation. There are little to no linear fabrics within the foliation fabrics. *LS-Tectonites is the perfect mix of the two, with both strong lineations and strong foliations. This is caused by the rotation of the grains around axes that are oriented along the trends of the folds.

Classification

*''S-tectonites'' (from the German, ''Schiefer'' for schist) have a dominant planar

and may indicate a flattening type of strain. This may also be due to a lack of minerals capable of giving a lineation e.g. in a phyllonite. *''L-tectonites'' have a dominant linear fabric and generally indicate a constrictional type of strain. This may be due to a lack of platey phases. *''L-S tectonites'' have equally developed linear and planar fabric elements and may indicate a

plane strain In continuum mechanics, the infinitesimal strain theory is a mathematical approach to the description of the deformation of a solid body in which the displacements of the material particles are assumed to be much smaller (indeed, infinitesimal ...

deformation. Many

mylonite Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a ...

s are L-S tectonites consistent with a simple shear deformation. *L-Tectonites (Lineations) indicate Constrictional Strain *S-Tectonites (Foliations) indicate Flattening Strain *L-S Tectonites (Plain strain) indicate both elongation and flattening strainhttp://structuralgeology.50webs.com/paget5.htm

References

Structural geology Metamorphic rocks {{petrology-stub