Terminology & Standards

About: Tect Task created this site about Terminology  to discuss relevant terms and words used in Structural Geology and Tectonics with the aim to build up a shared vocabulary or glossary for the SG and T community

Accomodation_zone: [Mechanical] The area between two subparallel, non-collinear, overlapping faults. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Active foliation: [Geometry-kinematics] Foliation that consists of microshear zones or other "active" planes. It is normally not parallel to the XY-plane of finite strain. Examples are shear band cleavage and some constrictional crenulation cleavages. (From Microtectonics, Passchier and Trouw, 2005)

Advection: [Geology-geodynamics] Transport of something from one region to another, for example transport of heat, vorticity or material in solution. (From Microtectonics, Passchier and Trouw, 2005)"

Anastomasing: Term used to describe the shape of some foliations: braided, dividing the rock into lenses. (From Microtectonics, Passchier and Trouw, 2005)"

Anastomosing: [Geometry] Term used to describe the shape of somefoliations: braided, dividing the rock into lenses. (From Microtectonics, Passchier and Trouw, 2005)"

Annealing: [Recrystallisation] Term from metallurgy used to indicate processes of recovery and static recrystallisation induced by passive heating of a previously deformed material. The term is also sometimes used for the interpretation of micro-structures in rocks."

Antitaxial fringe: [Geometry] Fringe in which the growth surface lies between the fringe and the core object. (From Microtectonics, Passchier and Trouw, 2005)"

Antitaxial vein: [geometry- kinematics] Vein with fibres growing along their contacts with the wall rock, i.e. along both outer surfaces of the vein (see also syntaxial vein and ataxial vein)

Antithetic fault: Antithetic fault is now commonly used for a fault that dips in the opposite direction to a related fault set. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Ataxial vein: [Geometry], vein with fibres growing along their contacts with the wall rock, i.e. along both outer surfaces of the vein (see also syntaxial vein and ataxial vein) (Passchier and Trouw, 2005)."

Axial planar foliation: [Geometry-mechanism] Foliation that is approximately parallel to the axial plane of folds. This term is used as an alternative term for secondary foliation."

Basement fault: [Geology] A basement fault cuts the basements rocks before the deposition of the cover sediments and that may be reactivated. Basements rocks are here used as pre-depositional with respect to the sediments infill (Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Basin-margin fault: [Geology] A basin margin fault marks the edge of and typically controls, a basin (Roberts and Yielding, 1991), (Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Bedding vein: [Geometry] Striped shear vein parallel to bedding in a sedimentary rock"

Bend fault: [Geology/map] When we can observe a variation in the orientation of a fault plane (Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Blastesis: [Mechanics] When in the upper crust P-T-etc. conditions are favorable for a metamorphic mineral to grow, nucleation can start. The small nuclei have a relatively high surface energy, which forms an energy barrier for their growth. The number of nuclei and their survival rate determines whether many small or a few large porphyroblasts form. This number depends on: (i) the availability of favorable nucleation sites; (ii) the driving force for the metamorphic reaction (overshoot of PT-conditions), (iii) transport rate of elements that form new mineral and elements that have to be removed to make space available [http://www.tectonique.net/mscourse2014/lectures/lec4a.html]."

Branch: [Topological] One or more faults that extend off a larger fault (e.g. Nevin, 1931; Butler, 1982). From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29"

Branch line: [Geometric] A branch line is a line along which two fault planes intersect (Butler, 1982). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)"

Cataclasis: [Geological/mechanical] Cataclasis is a process involving fragmentation of minerals or grains, with rotation of grain fragments, grain boundary sliding, grain flaking and fracturing, grain size reduction, and commonly volume change (Sibson, 1977). Cataclasis typically occurs along fault planes, within fault zones, or within deformation bands. (From Peacock et al. (2016), Glossay of fault and other fracture networks, J. Structural, Geology, 92, 12-29)" 

Cataclasite: Rock that forms at low-grade metamorphic conditions where deformation occurs mainly by macroscopic brittle fracturing."

Cleavage: [Geometry] Secondary foliation defined by a preferred orientation of inequant fabric elements. The name is usually restricted to fine-grained rocks such as slates and phyllites, but is also used by some authors as a general name for any secondary foliation except coarse layering"

Cleavage bundle: [Geometry] Local area of concentrated cleavage development, probably related with local high strain. (Passchier and Trouw, 2005. Microtectonics)"

Cleavage domain: [Geometry] Layer or lens with a relatively high content of elongate grains (such as micas or amphiboles) and low content of equidimensional grains (such as quartz, feldspar or carbonate). Together with microlithons they make up a spaced foliation. Micas in cleavage domains commonly have a preferred orientation parallel or at a small angle to the domain. (From Microtectonics, Passchier and Trouw, 2005)".

Cleavage dome: [geometry-structure] Dome-shaped structure, usually a graphite aggregate, attached to the crystal face of a porphyroblast. The structure is probably formed by porphyroblast growth. (From Microtectonics, Passchier and Trouw, 2005)"

Cleavage front: [Geometry] Boundary between rocks without cleavage and cleavage bearing rocks of the same lithology in an orogenic belt. Its synonym is cleavage lamella. (From Microtectonics, Passchier and Trouw, 2005)"

Closure temperature: The closure temperature of a geochronological system, as first defined by Dodson (1973) [https://goo.gl/vkRFJB], is the temperature of the rock at the time of its calculated isotopic age. Each geochronologic systems record different aspects of a geological event due to differences in their closure temperatures."

Closure Temperature: [Theory] The closure temperature theory was formalized by Dodson (1973) and defined as the temperature of a given system at the time of its apparent age."

Compositional layering: [Geology] Non-genetic term for an alternation of layers with different lithology. This may be bedding, igneous layering or a layering induced by secondary differentiation processes. See also differentiated layering. (From Microtectonics, Passchier and Trouw, 2005)."

Conjugate faults: [Geometry] Conjugate is a term that applies to two intersecting set of faults formed under the same regime of stress (Daubrée, 1878, cited by Dennis, 1967). Two conjugate faults have the opposite shear sense and the same angle (generally ~30 degrees) to the principal stress direction (Anderson, 1951). See also Peacock et al. (2000). Glossary of normal faults."

Constrictional strain: [Mechanism] Type of three-dimensional strain for which stretch < 1 along the intermediate strain axis. Constrictional strain produces a prolate (flattened cigar-like) strain ellipsoid in the absence of volumen change. (From Microtectonics, Passchier and Trouw, 2005)."

Contraction: Extension and contraction signify the strains that occur in most materials along the loading direction under the stress states of uniaxial tension and compression, respectively. An example of the usage of this terminology is given by Ramsay and Huber (1987, R. Marrett, D.C.P. Peacock / Journal of Structural Geology 21 (1999) 1057±1063 1059, p. 668), who connect positive tensile stresses with positive strain elongations and negative compresional stresses with negative contractional elongations''. Another term for contraction is shortening (e.g.Ramsay and Huber, 1983, p. 8). [http://www.sciencedirect.com/science/article/pii/S0191814199000206?via%3Dihub]"

Crenulation Cleavage: [geometry/mechanics]. It is a morphological classification of secondary foliations (Rickard, 1961). In particular, when we observe a spaced foliation, characterized by the alternation of cleavage domains and microlithons, the crenulation cleavage refers to the micro folds of an earlier foliation in the microlithons (Passchier and Trouw, 1986)."

Cross-bedding: [Geology-sedimentary primary structure]. In sedimentary rocks where the bedding planes within multiple layers have an orientation that is more or less inclined with respect to the separation planes between the beds. Generally, in a cross-bedding structure, the inclined bedding planes are smoothly curved and can be tangential to the separation plane at the base of the cross-bedded stratum (Sherbon Hills, elements of structural geology, 1963)."

Cut-off line: [Geometry] The cut-off refers to the trace or line of the fault that marks the boundary between a fault surface and a planar marker, such as strata, foliation, dike, etc., displaced by the fault."

Damage zone:  [kinematic and mechanical]. Location at which a major change in fabric (e.g., caused by pressure solution) is readily visible (Chester and Logan, 1986; Wu and Groshong, 1991), or the volume of deformed wall rocks around a fault surface that results from the initiation, propagation, interaction and build-up of slip along faults (Cowie and Scholz, 1992; McGrath and Davison, 1995; Kim et al., 2004; Choi et al., in press). Synonymous with deformation front and texture zone (Wu and Groshong, 1991)(Peacock et al (2016), Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)

Deformation: [Mechanism] Change in shape and orientation of objects or volumes of rock from an initial to a final state. We use the term deformation in this general sense, while the word strain has a more restricted significance, that is, the change in shape of an object or part of the rock. (Microtectonics, Passchier and Trouw, 2005)"

Deformation band: [Geological] Distinct bands at the microscale of different extinction that are obviously part of the same crystal. A more localised form of undulose extinction where some concentration of dislocation has taken place. In picture below they trend NE-SW (M. Jessell and P . Bons, CET/UWA Microstructure Course 2014; http://www.tectonique.net/mscourse2014/index.html)."

Deformation bands: [Mechanics/Geometry] Deformation bands are (1) tabular structural discontinuities having a continuous change in displacement, strength, or stiffness across a relatively narrow zone in porous rocks (Schultz and Fossen, 2008). (2) distinct bands of different extinction that are obviously part of the same crystal. a more localized form of undulose extinction where some concentration of dislocation has taken place [Passchier and Throuw, 2005]."

Deformation lamella (plural lamellae): Intracrystalline lamella of slightly different optical relief than the host grain, consisting of damaged crystal lattice or arrays of sub-microscopic inclusions"

Deformation lamellae: [Mechanics] Sharp-sided, narrow and repeating bands usually forming sub-parallel to a specific crystallographic orientation, such as the basal plane in quartz. can be due to a number of processes, but are commonly zones of concentrated slip on a given slip system. In picture below they trend NE-SW [http://www.tectonique.net/mscourse2014/glossary/glossary1.html]."

Deformation mechanism map: A diagram showing the conditions of stress and homologous temperature for which specific deformation mechanisms are dominantly, although not exclusively, active; each map is only valid for a specific mineral and grain size. (Microtectonics, Passchier and Trouw, 2005)"

Deformation partitioning: Local subdivision of the deformation pattern into domains with different deformation parameters such as strain and volume change, or with different dominant active deformation mechanisms. (Microtectonics, Passchier and Trouw, 2005)"

Deformation path: Path of a volume of rock from the undeformed to the deformed state, as seen in an external reference frame. Also, sum of the displacement paths for a volume of rock. (Microtectonics, Passchier and Trouw, 2005)"

Deformation phase: Period of deformation during which a group of structures has formed, separated from other structures by overprinting criteria. Successive deformation phases may merge into each other or may be separated by time intervals with little or no deformation, during which metamorphic conditions and the stress field may have changed (Passchier & Trouw, 2005, Microtectonics, Springer).

Density, fault: [Geology/Geometry] Density, when refers to a set of faults, indicates the measurements of the number of faults in a rock system."

Desiccation crack: [Geological] It is a process of opening of fracture formed by contraction of soft sediments, usually clay or mud (mud crack), as it dries. (From Peacock et al. (2016), Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)"

Detachement: [Geological/mechanical] A detachment is a term used in regional settings to indicate a zone of extensive, low-angle normal fault."

Deviatoric stress: non-hydrostatic or lithostatic component of stress defined as (σ n â€"σ mean), where σ n is normal stress on a surface and σ mean is the mean stress. (Microtectonics, Passchier and Trouw, 2005)"

Diagenetic strain: [Mechanism] Strain due to diagenetic compaction, usually resulting in a shortening normal to bedding and volume loss"

Differential stress: Non-hydrostatic or lithostatic component of stress, usually defined as (σ 1 â€"σ 3). (Microtectonics, Passchier and Trouw, 2005)"

Diffusion creep: [process-kinematics] Deformation due to migration of vacancies through the crystal lattice. (Microtectonics, Passchier and Trouw, 2005)"

Dilatation band: Type of deformation band in which fracturing led to volume increase of the gouge or cataclasite with respect to the original rock. (Microtectonics, Passchier and Trouw, 2005)"

Dip-slip: [Mechanics/geometry] The formation of strike-slip duplexes is best understood as a kinematic response to imposed boundary constraints, rather than by the stress-control or bulk strain approaches usually applied to wrench tectonics (Woodcock and Fischer, 1986. Journal of Structural Geology, Vol. 8, No. 7, pp.)."

Discontinuity: [geological and mechanical] A surface across which there is a variation in the mechanical behaviour of rocks, such as bedding planes or fractures (e.g., Fookes and Parrish, 1969) (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Disjunctive foliation: [Geometry] Secondary spaced foliation without fold hinges in the microlithons. If microlithons are wide and continuous, the term compositional layering is used as a synonym. (Passchier and Trouw, 2005, Microtectonics)"

Dislocation: [geometry-mechanism] Line defect in a crystal"

Dislocation climb: [Mecanism] Movement of a dislocation out of its slip plane, normally by migration of vacancies to the dislocation site"

Dislocation creep: [kinematics] Movement of dislocations in a crystal lattice by dislocation glide and climb. (Microtectonics, Passchier and Trouw, 2005)"

Dislocation density: [Geometry] Total length of all dislocations in a volume of material. (Microtectonics, Passchier and Trouw, 2005)"

Dislocation glide: [kinematics] Movement of dislocations in a crystal lattice without dislocation climb. (Microtectonics, Passchier and Trouw, 2005)"

Displacement path: [Geometry-mechanism] Path traced by a particle in a deforming rock from the undeformed to the deformed state, as seen in an external reference frame

Domain shape preferred orientation: [Geometry] Fabric of elongate lenses, each of which has a strong crystallographic preferred orientation different from that in neighbouring lenses. (Microtectonics, Passchier and Trouw, 2005).

Domino boudin: [Geometry] Type of asymmetric boudinage with short stubby boudins. (Passchier and Trouw, 2005)"

Domino_fault: [geometric and kinematic] A system of planar rotating normal faults, in which the dip of a particular stratigraphic datum is approximately constant (e.g., Twiss and Moores, 1992). Synonymous with bookshelf faults (e.g., Ramsay and Huber, 1987, Fig. 23.19) and with rotational planar normal faults of Wernicke and Burchfiel (1982)(From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Dragging microstructure: [Geometry] Strong curvature of a boundary between two grains of mineral A where it joins the contact with a mineral B (Fig. 3.34). This structure is interpreted to have formed when the grain boundary migrated and was pinned to some extend at the contact with mineral B."

Duplex: [geological and geometric] An arrangement of faults with the same shear sense that are geometrically- and kinematically-linked to form a series of lensoidal or sigmoidal horses, i.e., each pair of faults has two intersection points in map- or section-view. Duplexes have been described for thrust (e.g., Butler, 1982), normal (e.g., Gibbs, 1984) and strike-slip (Woodcock and Fischer, 1986) faults (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Epitaxy: [Mechanism] Preferential nucleation of a mineral on the lattice of another, with a fixed orientation relationship between the two crystal lattices (Passchier and Trouw, Microtectonics, 2005)"

Equigranular fabric: [Geometry] Fabric in which all grains have roughly equal size. (Passchier and Trouw, 2005, Microtectonics)"

Euhedral crystal: [Geometry] Crystal with well-developed crystal shape and crystal faces. (Passchier and Trouw, 2005, Microtectonics)."

Extension: A measure of how much longer a line or object has become due to deformation (Fossen, 2016).

External foliation: [Geometry] Foliation outside and immediately adjacent to a porphyroblast. It is commonly referred to by the abbreviation Se (e for external), and used in comparisons with the internal foliation (Si). (Passchier and Trouw, 2005, Microtectonics)."

Fabric [Geometry]: The complete spatial and geometrical configuration of all those components that are contained in a rock (Hobbs et al. 1976) and that are penetratively and repeatedly developed throughout the volume of rock under consideration. This includes features such as foliation, lineation, lattice preferred orientation and grain size. The term can also be defined as: the relative orientation of parts of a rock mass. (Passchier and Trouw, 2005, Microtectonics)."

Fabric attractor (FA): [Geometry-mechanism] Line or plane in space towards which material lines and some fabric elements rotate. (Passchier and Trouw, 2005, Microtectonics)"

Fabric element: [Nomenclature] Part of a fabric such as a foliation, lineation etc."

Fabric skeleton: [Technique-geometry] Crest lines on a contoured plot of crystallographic axes in a stereogram, used to describe lattice-preferred orientation patterns. (Passchier and Trouw, 2005, Microtectonics)."

Fault system: [Geology/mechamics] A fault system should be characterized by a movement of the rocks on either side. Fault zones that experience a sudden movement produce earthquakes.

Faults: they are shearing-mode fractures. i.e. fractures  where the wall rocks move sub-parallel to the fracture. This term include faults and fault zones as defined by as “a plane of fracture which exhibits signs of differential movement of the rock mass on either side of the plane (Price, 1966).

Finite deformation: [Mechanism] Deformation accumulated over a finite period of time. (Passchier and Trouw, 2005, Microtectonics)"

Finite displacement vector: [Geometry-mechanism] Vector connecting particles in the undeformed and deformed state for finite deformation finite strain "strain accumulated over a finite period of time"

Finite strain: [Mechanism] Strain accumulated over a finite period of time, (Passchier and Trouw, 2005, Microtectonics)."

Flower structure: [Geometric] A flower structure is a system of faults that splay upward within a strike-slip fault zone (Harding and Lowell, 1979). (From Peacock et al. (2016), Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Foliation: [Geometry-mechanism] Planar fabric element that occurs penetratively on a mesoscopic scale in a rock. Primary foliation includes bedding and igneous layering; secondary foliations are formed by deformation induced processes. Joints are not normally considered as foliations since they are not penetrative on a mesoscopic scale. (From Passchier and trouw, 2005, Microtectonics).

Fracture cleavage: [Disambiguate term] Alternative and outdated term for disjunctive cleavage. The use of this term is discouraged because of its (commonly erroneous) genetic implication.

Fractures: [Mechanics] The term fracture is commonly used to cover a range of structures, including faults, joints, veins, hydraulic fractures, and magma-filled cracks (such as dykes and sills), (Schultz and Fossen, 2008; Peacock et al., 2016). A fracture corresponds mechanically to a sharp structural discontinuity having a local reduction in strength and/or stiffness and an associated increase in fluid conductivity between the opposing pair of surfaces.

Fringe: [Structure] Body of fibrous crystalline material formed adjacent to a relatively rigid core object during progressive deformation.

Geochronology: [Technique] Geochronology has been applied to rocks since the beginning of the 19th century to date rocks formation (e.g. Holmes, 1913). The thermal effects on radioisotopic ages were recognized a few decades later (Hurley, 1954). Using this fundamental discovery, the concept of comparing dates constrained with different radiometric techniques the cooling history of rocks was intuited starting from the early 1960s in few interesting pioneering work both in the Alps (Amstrong et al., 1966) and the Himalaya (Krummenacher, 1961). Armstrong et al., (1966), used  Rb-Sr and K-Ar on biotite, white mica, and sanidine minerals to define their ages as the time of the cooling of the rocks during Alpine metamorphism. They also predicted, using different isotopic systems with two different closure temperatures, how the two system can be different and can be used to infer the rate of cooling of a certain region. Later, a work by Wagner et al.(1979), used apatite fission tracks data to constrain the exhumation rate of the Bergell intrusive body (Central Alps) and to recursively restore the original position of a set of boulders found in the Po plain (Italy), eroded during late Oligocene.[Extracting erosion and exhumation patterns from detrital thermochronology: an example from the eastern Himalaya. VU, Amsterdam PhD Manuscipt by Gemignani, L., 2018].

Geodynamic: It is the science describing the dynamic processes that govern the large scale structure of earth. The science of geodynamics and tectonics includes the description and interpretation of a large variety of geological processes that operate in the earth [https://www.eolss.net/sample-chapters/C01/E6-15-02.pdf].

Ghost structure: [Geometry] Outline of an overgrown mineral in a porphyroblast visible as a local relative scarceness of inclusions.

Gneissosity: [Geology] General term for foliation in a gneiss. Use of this term is discouraged because of its vague connotation; several types of foliation (layering, schistosity) may occur in the same gneiss. (Passchier and Trouw, 2005. Microtectonics).

Grain: [Geology-Geometry] Equivalent of crystal in metamorphic rocks. In sedimentary rocks a detrital grain may contain several crystals. Passchier and Trouw, 2005. Microtectonics.

Grain boundary: [Geometry] Planar domain of distorted crystalline material between two crystal lattices of different orientation and/or nature. (Passchier and Trouw, 2005).

Grain boundary area reduction: [Mechanism] Leading to reduction in the total surface area of grain boundaries in an aggregate. The process operates spontaneously in response to the decrease in internal free energy that a grain aggregate gains by decreasing the area of (high-energy) grain boundaries; it leads to straight grain boundaries and large grains. (Passchier and Trouw, 2005).

Grain_boundary_migration: [Mechanism] The migration of a grain boundary through a solid crystalline material. (Passchier and Trouw, 2005).

Grain shape foliation: The preferred shape orientation distribution of grains in a rock. Grain boundary alignment: The preferred alignment of grain boundaries in a rock, which does not necessarily directly correlate with GSF (M. Jessell & P. Bons, CET/UWA Microstructure Course 2014; http://www.tectonique.net/mscourse2014/index.html)

Granoblastic fabrics: [Mechanics] In high-grade gneissic rocks, mineral grains are usually bounded by straight or slightly bent grain boundaries which define regular, polygonal pattern, known as granoblastic fabric. This fabric develops usually where diffusion processes and recrystallization occur relatively fast enhanced by high to really high-grade metamorphic conditions [Passchier, C.W., Myers, J.S. and Kröner, A., 2012. Field geology of high-grade gneiss terrains. Springer Science & Business Media.].

Growth inclusion: [Geometry] Small mineral grain included in a porphyroblast, usually parallel or orthogonal to crystal faces. Such inclusions are thought to have formed during growth of the porphyroblast and do not represent part of the matrix that was overgrown by the porphyroblast, as for passive inclusions.

Habit: [Geometry-mineralogy] Crystal shape, specifically referring to the relative development of individual crystal faces (e.g. prismatic habit; tabular habit). (Passchier and Trouw, 2005).

Hardening: [Mechanism] Increasing resistance to deformation, expressed as increasing differential stress at constant strain rate, or decreasing strain rate at constant differential stress. (Passchier and trouw, 2005).

H-Block: [Geometric/mechanic] In extended continental margins at the onset of the thinning process a major crustal block, about 15-20 km-thick, formed in between necking zones and experienced a stage of pronounced uplift [“H block” of Lavier and Manatschal, 2006].

Helicitic fold: [Geometry] Pattern of inclusions in a porphyroblast resembling a fold and thought to have formed by overgrowth of a pre-existing fold in the matrix. (Passchier and Trouw, 2005).

High-temperature grain boundary migration (GBM) recrystallisation: [Mechanism] Recrystallisation by migrating grain boundaries throughout old grains in response to differences in dislocation density between two grains. (Passchier and Trouw, 2005).

Hydrostatic pressure: [Mechanism] Pressure due to the weight of a column of water acting equally in all directions. (Passchier and Trouw, 2005).

Φ-type_object: [Geometry] mantled porphyroclast with symmetric wings (no stair stepping is developed).

Θ-type_object: [Geometry] Mantled porphyroclast without wings. (From Microtectonics, Passchier and Trouw, 2005).

Δ-type_object: [Geometry-kinematics]: Mantled porphyroclast with thin asymmetric wings of mantle material fixed to opposite sides of the porphyroclast and stretching into the matrix. The shape resembles the Greek letter δ. (From Microtectonics, Passchier and Trouw, 2005).

Σ-type_object: [Geometry-Kinematics] Mantled porphyroclast with a geometry resembling the Greek letter σ. (From Microtectonics, Passchier and Trouw, 2005).

Idioblastic: A porphyroblast that in a deforming matrix regulate its boundary by its own crystallography  http://www.tectonique.net/mscourse2014/glossary/glossary4.html#idiobastic].

Igneous foliation: [Geometry] Primary foliation defined by a preferred orientation of phenocrysts or other fabric elements in a tectonically undeformed igneous rock.

Imbricate: [Geometric] When thrust sheet splay of a single thrust.

Impingement microcrack: [Geometry-Mechanism] Small fracture in a grain formed due to local stress concentration where the grain is in contact with another grain or object. Passchier and Trouw, 2005.

Inclusion tail: [foliation/mechanics] The usual rigidity of the porphyroblasts protects the inclusion trail pattern from further deformation. Porphyroblasts with inclusions thus provide a frozen-in picture of the foliation at the time of their growth. This allows determination of the timing of growth (phases) relative to deformation or tectonic phases.

Incremental deformation: Infinitely small deformation.

Incremental displacement vector: [Geometry-mechanism] Vector connecting particles in the undeformed and deformed state for incremental deformation. (Passchier and Trouw, 2005).

Inequigranular fabric: [Mechanism-geometry] A fabric showing inhomogeneous distribution of grain size, e.g. bimodal with large grains of approximately equal size in a fine-grained equigranular matrix. (Passchier and Trouw, 2005). [http://www.tectask.org/]

Internal foliation: [Mechanism] Foliation defined by the preferred orientation of passive inclusions in a porphyroblast, thought to mimic the orientation and geometry of a foliation that was overgrown by the porphyroblast. The abbreviation Si (i for internal) is commonly used for internal foliation. Si is often used in comparison with the external foliation Se. (Passchier and Trouw, 2005).

Intracrystalline deformation: [Mechanism] Intracrystalline deformation is a process that occurs at crystal lattice scale when crystal deforms internally without brittle fracturing by movement of intracrystalline (lattice) defects (Passchier and Trouw, 1998).

Intracrystalline deformation: In a metamorphic rock, the deformation can deform internally a crystal by the movement of the so-called lattice defect without brittle fracturing. Dislocations of crystals are not always observable in the optical scale and TEM instrumentation can be required. However, the effect of the presence of aggregates of single similar dislocation in a crystal lattice may be observable as a bend of the crystal’s surface.  In this case, the crystal does not extinguish homogenously if observed with crossed polars this phenomenon is known as undulose extinction.

Isochore: [Theory] A line on a PT diagram showing the variation of the pressure of a fluid with temperature, when the volume of the fluid is kept constant.

Isotope geochronology: [Technique] Isotope geochronology is the science of determining the absolute age of the Earth and planetary materials. Geochronology is based on the measurement of the accumulated amount of radiogenic isotopes over a determinable time period.

Isotope provenance: [Technique] Isotope provenance is a branch of geochronology in which isotopic systems are used as a proxy to infer the origin of eroded sediments. For provenance purpose, single-grain age dating is routinely used for assessing the provenance using multi-minerals dating approaches. Some of the most applied techniques are U-Pb dating of zircons, fission tracks analysis of zircon and apatite, 40Ar/39Ar dating of white mica, biotite, and(U-Th)/He on apatite and zircon. Generally, U-Pb dating is considered to constrain crystallization ages whereas the other techniques yield in most cases the cooling ages (Bernet and Spiegel, 2004).

Isotropic: [Material properties] Term indicating that a material property is of equal magnitude in all directions; this may refer to birefringence of light, to growth rate, grain boundary energy, elastic strength, etc. (opposite of anisotropic) jog – step in a planar structure such as a fault.

Joint: [Ggeological] Defined by the Oxford English Dictionary (1989) as “a crack or fissure intersecting a mass of rock; usually occurring in sets of parallel planes, dividing the mass into more or less regular blocks”, with first usage attributed to Holland (1601). Price (1966) defines joints as “cracks and fractures in rock along which there has been extremely little or no movement”, with some authors describing shear joints having a shear displacement (e.g., Hancock, 1985). Pollard and Segall (1987) show that joints have two parallel surfaces that meet at the fracture front, that these surfaces are approximately planar, and that the relative displacement of originally adjacent points across the fracture is small compared to fracture length. Pollard and Aydin (1988) suggest that joints are generally associated with the opening mode, whereas faults are associated with the shearing modes, and propose that the word “joint” be restricted to those fractures with field evidence for dominantly opening displacements. We suggest that fractures with dominantly opening displacements but that have mineral fills should be called veins. Pollard and Aydin (1988) criticise definitions of joints as having no discernible displacement, because they would not exist without some displacement. They are particularly critical of the concept of “shear joints”, which they regard as small faults. Pollard and Aydin (1988) define, describe and illustrate various joint geometries (e.g., cross, diagonal, dip, ladder, normal, polygonal and strike joints), mechanisms (e.g., contraction, cooling, shrinkage and unloading joints) and surface patterns (e.g., hackle and rib marks and plumose structures). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Kinematic dilatancy number: [Method] (Ak) measure of the dilation rate of flow, normalised against strain rate; dimensionless number. (Passchier and Trouw, 2005).

Kinematic vorticity number: [Method] (Wk) measure of the vorticity of flow, normalised against strain rate; dimensionless number. (Passchier and Trouw, 2005).

Kink bands: [Geometry/mechanics] Parallel sided zone of differently oriented crystal within a single grain, with no special ""twin orientation"" between zone and host crystal. Often form either by a polygonization process where a gently curved crystal resolves itself into several low defect bands separated by tilt wall boundaries, or by a gradual rotation and growth of the zone from a small elongate nucleus. The former are common in high temperature olivine, the latter in micas & kyanites [http://www.tectonique.net/mscourse2014/glossary/glossary1.html].

Lattice-preferred orientation (LPO): [Counting method] Statistical preferred orientation of the crystal lattices of a population of crystals in a rock. In older texts also referred to as texture, crystallographic fabric or crystallographic preferred orientation. (Passchier and Trouw, 2005).

Lens: [geometric] A fault-bound zone of relatively weakly deformed host rock within a fault zone (e.g., Swanson, 2005). Also called shear lens (e.g. Swanson, 1990).(From Peacock et al. (2016), Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Lepidoblastic fabric: [Geometry] Planar fabric defined by the preferred orientation of tabular or platy crystals (from Greek ‘λεπις’ – scale).

Lineament: [Geological] A linear topographic feature of regional extent that is thought to reflect crustal structure. (From Peacock et al. (2016), Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Linear shape fabric: [Geometry] Fabric defined by the elongate shape of grains or grain aggregates. A type of shape preferred orientation.

Lineation: [Geometry] Linear fabric element that occurs penetratively on a mesoscopic scale in a rock. Striations and fibres are not normally considered to be lineations since they do not occur penetratively on a mesoscopic scale. (Passchier and Trouw, 2005).

Lithostatic pressure: [Mechanism] Pressure at a point in the Earth due to the weight of the overlying column of rock. Lithostatic pressure at a point is uniform in all directions by definition. (Passchier and Trouw, 2005).

Mantled porphyroclast: [Object/Geometry] Porphyroclast with an elongated mantle of the same mineral composition, stretched in the direction of the foliation. It is inferred to have formed at the expense of the porphyroclast by recrystallisation in its rim. Mantled porphyroclasts are common in mylonites and are used to determine sense of shear. See also δ-type object, σ-type object and strain shadow. (Passchier and Trouw, 2005).

Mean stress: [Process] Hydrostatic or lithostatic component of stress, of equal magnitude in any direction. (Passchier and Trouw, 2005).

Mechanical stratigraphy: [geometric and mechanical] where the stratigraphy is defined in terms of rheology, such that different mechanical units control the types or frequencies of structures (e.g., Corbett et al., 1987). Also see bed-bound fault or other type of fracture and layer-bound fault or other type of fracture. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Metamorphic cycle: [Large scale process] Cycle of changing pressure and temperatura experienced by a volume of rock. (Passchier and Trouw, 2005)-

Metamorphic event: [Process] Episode of metamorphism, characterised by changes in mineral assemblage in a volume of rock. (Passchier and Trouw, 2005).

Mica fish: [Geometry] Lensoid mica grain common in mylonites. A type of mineral fish. Their asymmetry can be used to determine sense of shear. (Passchier and Trouw, 2005).

Microcracs: [Mechanics] Microcracks are planar discontinuities in rocks on the grain scale or smaller, commonly with some dilation but with negligible displacement. They may nucleate on minor flaws in the crystal lattice, fluid or solid inclusions in crystals, or on grain boundaries (Tapponier and Brace, 1976; Passchier and Trouw, Michrotectonics 2005).

Microcrack: [geometric and mechanical] Fractures with microscopic-scale lengths, apertures, etc. (e.g., Robertson, 1960). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Microlithon: [Geometry] Layer or lens with a relatively small degree of preferred orientation as compared to cleavage domains. A crenulated older foliation may be present in microlithons. Together with cleavage domains, microlithons make up a spaced foliation. (Passchier and Trouw, 2005).

Microstructures: [Geology/mechanics/kinematics] Microstructures occur during deformation phase events within a material. The term ‘microstructure’ is used to describe the appearance of the material on the nm-cm length scale.

Millipede structure: [Geometry] Inclusion pattern in a porphyroblast resembling an Australian millipede (Bellaria sp.). (Passchier and Trouw, 2005).

Mimetic growth: [Mechanism] Growth of minerals controlled by preexisting grain arrangements (Vernon 1976).

Mineral fish: [Geometry] Elongate lozenge- or lens-shaped single crystal (porphyroclast), usually oblique to the mylonitic foliation, embedded in a finer grained matrix in a mylonite. (Passchier and Trouw, 2005).

Mineral lineation: [Geometry] Grain lineation composed of crystals of the same mineral with an acicular crystal habit such as amphiboles, pyroxenes, sillimanite and tourmaline. (Passchier and Trouw, 2005).

Mode I: [mechanical] fracture propagation by extension (e.g., Atkinson, 1987, Fig. 1.1). Also see extension fracture, tension fracture and tensile fracture. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Mode II: [mechanical] fault propagation by in-plane shearing or sliding, i.e., perpendicular to the fault tip line (e.g., Atkinson, 1987, Fig. 1.1). Also see fault. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Mode III: [mechanical] fault propagation by anti-plane shearing or tearing, i.e., parallel to the fault tip line (e.g., Atkinson, 1987, Fig. 1.1). Also see fault. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Mortar structure: [Geometry] Porphyroclast surrounded by an finegrained aggregate of the same mineral. Mortar structure is similar to core-and-mantle structure but the new grains are smaller. A mortar structure is not necessarily formed by recrystallisation, but possibly by cataclasis or a combination of both. The use of this term is discouraged because of its (commonly erroneous) genetic implication of “mechanically crushed rock”.

Mylonite: [Geology/mechanism] Strongly deformed rock from a ductile shear zone, commonly with a planar foliation and usually with a stretching lineation. Evidence for high strain such as quartz ribbons and porphyroclasts in a more fine grained matrix are common. Mylonite was originally (Lapworth 1885) defined as a brittle fault rock, but mylonites are now thought to have formed predominantly by crystalplastic flow of the matrix, although some minerals suspended in the matrix may show brittle fracturing. The word derives from the Greek ‘μυλων’, a mill. (Passchier and Trouw, 2005).

Mylonitic foliation: [Geometry/mechanism] Type of secondary foliation developed in mylonites.

Myrmekite: [Geometry] Symplectite of quartz and plagioclase, commonly adjacent to K-feldspar, indicating replacement. (Passchier and Trouw, 2005).

Nabarro-Herring creep: [Mechanism] Solid state diffusion through the crystal lattice. (Passchier and Trouw, 2005).

Nematoblastic: [Fabric] Nematoblastic refers to a fabric of metamorphic rocks characterized by a predominance of elongated grains that are organized along a preferred linear orientation. This term is nowadays substituted by the assessment of the mineral lineation (Passchier and Trouw, 1986).

Nematoblastic fabric: [Geometry] Linear fabric defined by preferred orientation of acicular or prismatic crystals (from Greek ‘νημα’ – thread). (Passchier and Trouw, 2005).

Non-coaxial: [Mechanism] Term used for flow or progressive deformation in which material lines that were initially parallel to ISA rotate to another orientation. (Passchier and Trouw, 2005).

Normal stress: Component of stress acting on a plane (avector), normal to that plane. (Passchier and Trouw, 2005).

Object lineation: Lineation formed by preferred orientation of elongate monocrystalline or polycrystalline objects. Passchier and Trouw (2005).

Oblique foliation: [Geometry-shape] Shape- preferred orientation oblique to mylonitic- or other foliation. Oblique fabrics are a type of grain shape preferred orientation that commonly develops in response to noncoaxial flow. (Passchier and Trouw, 2005).

Oblique-Si porphyroblast: [Geometry] Porphyroblast with a straight inclusion pattern at an angle with the foliation in the matrix. Passchier and Trouw, 2005.

ODF: Orientation distribution function. Function describing the three-dimensional orientation of crystals in a rock. (Passchier and Trouw, 2005, Microtectonics).

Opening trajectory: [Geometry] The inferred trajectory in space that an imaginary point on the wall of a vein has traced during the process of vein opening, in a reference frame fixed to one of the vein walls or the median line. (Passchier and Trouw, 2005, Microtectonics).

Ophitic microstructure: Common igneous fabric that consists of elongate plagioclase grains which are completely surrounded by pyroxene grains. This microstructure is found in basaltic and gabbroic rocks. (Passchier and Trouw, 2005, Microtectonics).

Orientation contrast (OC): SEM-image generated using backscattered electrons where grey tones represent different orientation of material in the sample. (Passchier and Trouw, 2005, Microtectonics).

Orientation family: Isolated (in 2D) set of grains with the same crystallographic orientation which were once part of same grain, but have been isolated by grain boundary migration. Grains A, B & C below all have the same crystallographic orientation mortar texture rock showing bimodal grain size distribution with large grains surrounded by a matrix of smaller grains (M. Jessell and P. Bons, CET/UWA Microstructure Course 2014; http://www.tectonique.net/mscourse2014/index.html)"

Oscillatory zoning: Growth zoning in undeformed crystals, common in phenocrysts in igneous rocks. (Passchier and Trouw, 2005, Microtectonics).

Ostwald ripening: [Mechanism] Growth of few grains to a larger size at the cost of their neighbours. The process is similar to GBAR but more commonly used to describe a porous material with a pore fluid or melt between grains. (Passchier and Trouw, 2005, Microtectonics).

Overprinting: [Mechanism] The partial erasure of a feature in the rock fabric by a younger feature. (Passchier and Trouw, 2005, Microtectonics).

Palaeostress: stress value reached in a rock at some time in geological history. (Passchier and Trouw, 2005, Microtectonics).

Passive foliation: Foliation that is rotating passively towards the fabric attractor. Passive foliations are subparallel to the XY-plane of finite strain. Examples are most types of continuous foliations. See also active foliation. (Passchier and Trouw, 2005, Microtectonics).

Passive inclusion: [Geometry-mechanism] Mineral grain included in a porphyroblast or larger grain in the rock matrix. Such inclusions are thought to represent a fragment of the matrix which was overgrown by the porphyroblast and passively included in its crystal lattice without significant displacement or rotation. (Passchier and Trouw, 2005, Microtectonics).

Pencil cleavage: [Mechanism/Geometry] Term used for a structure where two intersecting foliations are of equal grade of development, causing the rock to fracture into pencil-shaped fragments upon weathering. The term is mostly used for diagenetic cleavage intersected at a high angle by tectonic cleavage. (Passchier and Trouw, 2005, Microtectonics).

Penetrative fabric element: A fabric element that occurs penetratively throughout a rock. A foliation is an example of a penetrative fabric element. We use the word penetrative to mean: at the scale of observation. In thin section this means: down to the scale of individual mineral grains. (Passchier and Trouw, 2005, Microtectonics).

Perthite: [Mechanism] K-feldspar with inclusions of plagioclase, formed by exsolution of the albite solid solution in K-feldspar. (Passchier and Trouw, 2005, Microtectonics).

Petrochronology: Petrochonology is a complementary branch of the thermochronology that refers to the specific use that petrologist does with chronologic dates. The need of understanding the rocks formation processes and not only their cooling evolution in a temporal framework has led to coining this new discipline[https://goo.gl/zL3hXw].

Phenocryst: large, commonly euhedral single crystal in an igneous rock or pseudotachylyte, thought to have formed by growth from a melt. (Passchier and Trouw, 2005, Microtectonics).

Phillonite: Strongly sheared rock made mainly by phyllosilicates. See also: Phyllonite.

Phyllonite: Micaceous mylonite, sometimes (erroneously) used for ultramylonite (from Greek ‘φυλλον’ – leaf). (Passchier and Trouw, 2005, Microtectonics).

Pinning microstructure: [Geometry] Strongly indented boundary between two grains of a mineral.

Planar shape fabric: [Mechanism] Planar fabric defined by the shape of deformed flattened grains or grain aggregates. A type of shape preferred orientation. (Passchier and Trouw, 2005, Microtectonics).

Plane strain: Type of three-dimensional strain for which Y/Z=X/Y. In the absence of volume change this means that Y=1. (Passchier and Trouw, 2005, Microtectonics).

Platelet lineation: [Mechanism] Lineation defined by planar minerals such as micas which share a common axis. (Passchier and Trouw, 2005, Microtectonics).

Platy quartz: Monocrystalline quartz ribbon with few or no intracrystalline deformation structures, common in high-grade gneisses. (Passchier and Trouw, 2005, Microtectonics).

Poikiloblast: A large grain of [[Xenoblast]] that during metamorphism has been extremely enriched in inclusions[http://www.tectonique.net/mscourse2014/glossary/glossary4.html#poikiloblast].

Point defect: Defect in a crystal lattice where a lattice element is missing (vacancy) or additional (interstitial). (Passchier and Trouw, 2005, Microtectonics).

Polygonal fabric: Fabric composed of crystals with straight grain boundaries, commonly with anhedral or subhedral crystals. (Passchier and Trouw, 2005, Microtectonics).

Porphyroblast: [Mechanics] A grain larger than the surrounding matrix. Mineral grains that have recrystallized during or after the development of a structure (foliation, lineation). The porphyroblasts may have re-equilibrated to new conditions at that stage. If the mineral has grown during deformation can be dated with respect to a single phase deformation. However, the mineral grains could have only rotated to form a fabric, without recrystallization and re-equilibration."

Porphyroclast: [geometry/mechanics] In metamorphic fabric a grain considerably larger than its matrix [http://www.tectonique.net/mscourse2014/glossary/glossary4.html#porphyroclast] that rotated during the deformation process maintaining its relict phase."

Pressure fringe: Alternative, but genetic term for strain fringe. (Passchier and Trouw, 2005, Microtectonics).

Pressure Solution: [Mechanics] Pressure solution is an important deformation mechanism that occurs in rocks that contain intergranular fluid. Pressure solution is localized where high stress occurs in the grain and grains boundary present high angle with the direction of shortening (Passchier and Trouw, 1998).

Primary foliation: Foliation that was present in a sedimentary or igneous rock before deformation. Primary foliation includes bedding and igneous layering.

Process zone: Domain in front of a propagating fault where microcracks form in grains, then link to a network, then separate to form brittle fault rock. (Passchier and Trouw, 2005, Microtectonics).

Progressive deformation: Process of the accumulation of deformation with time. (Passchier and Trouw, 2005, Microtectonics).

Propagation: [mechanical] Increase in length and area of a fault or other type of fracture or fault or other type of fracture zone, commonly involving an increase in displacement. Propagation has been described for dykes (e.g., Okamura et al., 1988), faults (e.g., Walsh and Watterson, 1988; Reches and Lockner, 1994), veins (e.g., Grimm and Orange, 1997). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Protomylonite: Weakly to moderately deformed rock in a shear zone, transitional between the undeformed wall rock and a mylonite. Also a mylonite with 10–50% matrix. (Passchier and Trouw, 2005, Microtectonics).

Proton induced gamma-ray emission: Method for accurate quantitative chemical analysis using proton induced gamma-rays. (Passchier and Trouw, 2005, Microtectonics).

Proton induced X-ray emission: Method for accurate quantitative chemical analysis using proton induced X-rays. (Passchier and Trouw, 2005, Microtectonics).

Pseudomorph: [mechanics] A pseudomorph is a secondary mineral or an aggregate of secondary mineral which has substituted the crystal-chemistry composition of the previous without altering its original shape. A common example of the pseudomorphic reaction is when the cubic shape of quartz is maintained after fluorite or serpentine after olivine. The orientation or cleavage of the mineral shape can be used as a tool to recognize the older phase.

Pseudotachylyte: Dark brittle fault rock occurring in veins and fractures in host rocks with low porosity. Pseudotachylyte is thought to form by local melting of a host rock along a fault in response to seismic activity on the fault and associated local generation of frictional heat. The name was derived from ‘tachylyte’ (basalt glass) occurring in settings that could not be explained by igneous activity.

Pull-apart: [geometric and kinematic] A rhomb-shaped opening along an extensional bend on a fault or at an extensional step between two faults (e.g., Peacock and Anderson, 2012). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Pure shear: The deformation of a volume of material occurring along the x-axis with no change of its original area it is defined as pure shear. The deformation of the axis of the ellipsoid does not rotate and the incremental and finite strain ellipsoids are coaxial.

Pure shear flow: A special type of coaxial flow, usually defined as having no stretch along the intermediate principal ISA. (Passchier and Trouw, 2005, Microtectonics).

Quartz ribbon: [Geometry] Highly elongated disc- or lens-shaped crystal or aggregate of quartz, common in mylonites and high-grade rocks. In thin section the crystals are ribbon-shaped, hence the name. Quartz ribbons form by flattening of originally equidimensional quartz grains, or possibly by migration of grain boundaries to form single large grains from more fine-grained parent aggregates. They may exhibit undulose extinction, or be recrystallised into polycrystalline ribbons. (Passchier and Trouw, 2005, Microtectonics).

Reaction softening: [Mechanism] Softening induced by the growth of new minerals which are more easily deformable than minerals of the host rock. (Passchier and Trouw, 2005, Microtectonics).

Reactivation: [kinematic] Renewed displacement on a fault that has undergone a prolonged period of inactivity (e.g., Shephard-Thorn et al., 1972; Sibson, 1985). The different displacement events may or may not be of the same sense. Also see trailing. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Recovery: [Geometry/metamorphism] Recovery processes are enhanced at higher temperatures and occur both during deformation and subsequent to it, but are typically swamped by deformation processes during deformation [http://www.tectonique.net/mscourse2014/lectures/lec2.html]."

Recrystallisation: [Mechanism] Rearrangement of crystalline matter to a modified set of crystals by migration and modification of grain boundaries. Recrystallisation does not necessarily involve chemical changes. It usually involves a decrease or increase in the crystal size. (Passchier and Trouw, 2005, Microtectonics).

Relay ramp: [geometric and kinematic] Zone of kinematic linkage between overlapping, geometrically uncoupled, sub-parallel faults, where strain is relayed from one fault to the other (Larsen, 1988; Peacock and Sanderson, 1991; Rotevatn et al., 2007). If the faults bounding the relay ramp become geometrically coupled, a breached relay (Trudgill and Cartwright, 1994) is formed. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Residual stress: [mechanics] In a rock, the stress can be preserved as residual of a previous external force in a stress regime that has changed. The elastic strain can be preserved over time as residual stress.

Rheology: Study of the deformation and flow of matter, more specifically the mechanics of flow. (Passchier and Trouw, 2005, Microtectonics).

Ribbon grains: Grains showing large aspect ratios sitting in a finer grained, more equant matrix of same mineralogy. Can form by flattening of individual grains, grain boundary migration, coalescence of two grains with same orientation, or rotation of neighbouring grain's lattices into same orientation (M. Jessell and P. Bons, CET/UWA Microstructure Course 2014; http://www.tectonique.net/mscourse2014/index.html).

Riedel shears: [Geometry/mechanism] A term for echelon fault strands formed early in a progressive deformation sequence; these R-shears (or conjugate R'-shears) are later linked by P-shears across their stepovers to form a continuous slip surface, called a principal-displacement surface or D-shear Named after clay deformation experiments by W. Riedel. (Passchier and Trouw, 2005, Microtectonics).

Secondary foliation: [Process/geometry] Foliation developed in response to deformation and/or metamorphic processes in a rock in the solid state. (Passchier and Trouw, 2005, Microtectonics).

Sector zoning: Preferential incorporation of passive inclusions in specific zones of a crystal. (Passchier and Trouw, 2005, Microtectonics).

SEM: Scanning electron microscope:

Separatrix: [Geometry] Imaginary surface in inhomogeneous flow, separating different flow patterns. (Passchier and Trouw, 2005, Microtectonics).

Shape preferred orientation (SPO): [Mechanism] Preferred orientation of elongate or planar aggregates or grains in a volume of deformed rock. There are grain-, aggregate and domain shape preferred orientations. (Passchier and Trouw, 2005, Microtectonic.

Shear band: [Geometry] Minor shear zone with lift and slip of the same sense.

Shear band boudinage: Type of asymmetric boudinage with elongate boudins separated by shear bands. (Passchier and Trouw, 2005, Microtectonics).

Shear band cleavage: [Geometry] Structure with shear bands, with a similar aspect as crenulation cleavage. The older foliation is apparently extended and not shortened as in crenulation cleavage. Shear band cleavages are common in mylonites and can be divided into two types; C-type and C'-type (the latter is also known as extensional crenulation cleavage).

Shear joint: [geometric and kinematic] A joint that displays and was formed by a “minor” shear displacement (e.g., Qidong and Peizhen, 1982). The term is rejected by Pollard and Aydin (1988) because any shear displacement would make the fracture a fault. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Shear sense indicator: [Geometry] Structure with a monoclinic symmetry that can be used to find the sense of shear in a mylonitic or protomylonitic rock. (Passchier and Trouw, 2005, Microtectonics).

Shear strain:  (γ ) – (1) tangent of the angle by which a line A, originally orthogonal to a line B, rotated with respect to B in finite deformation; (2) - tangent of the angle by which a line initial normal to the boundary of a shear zone rotated with respect to that boundary in finite deformation. Strain in shear zones is commonly expressed as shear strain. (Passchier and Trouw, 2005, Microtectonics).

Shear stress: [Vector] Component of stress acting on a plane (a vector), parallel to that plane.

Shear vein: [Geometry/mechanism] Vein formed by opening with a major shear component. (Passchier and Trouw, 2005, Microtectonics).

Shear zone: Planar zone of relatively intense deformation in which progressive deformation is non-coaxial. (Passchier and Trouw, 2005, Microtectonics).

Sheath fold: [Geometry] Strongly non-cylindrical fold in the form of a sheath, usually oriented parallel to a stretching lineation. Sheath folds are common in shear zones and especially in mylonites. (Passchier and Trouw, 2005, Microtectonics).

Schistosity: Secondary foliation defined by preferred orientation of inequant fabric elements in a medium to coarse-grained rock. Individual foliation-defining elements (e.g. micas) are visible with the naked eye. Sometimes used as a general term for any secondary foliation. (Passchier and Trouw, 2005, Microtectonics)"

SHRIMP: Abbreviation for sensitive high resolution ion microprobe – SIMS type instrument that can analyse small parts of individual grains. Used to date parts of zoned or inhomogeneous mineral grains.

Sigmoid: lozenge-shaped polycrystalline lens in strongly deformed rocks with a shape similar to sigma-type mantled porphyroclasts. A sigmoid is is an aggregate of small grains without a central clast (Passchier & Trouw, 2005, Microtectonics).

Simple shear: simple shear of a material is its 3-d constant volume change (Twiss and Moores, 1992; Davis and Reynolds, 1996). This process implies the rotation of the ellipsoids finite strain axes.

SIMS: Abbreviation for Secondary Ionization Mass Spectrometry.

Slaty cleavage: [Mechanism/Geometry] Secondary foliation, either continuous or spaced in fine-grained rocks (slates and phyllites). Spacing up to 0.01 mm is included in the definition of slaty cleavage.

Slickenfibres: [Geometry/ mechanism] Scratches or linear markings on a slickenside that indicate slip direction along the slickenside. Also known as striae (singular stria). (Passchier and Trouw, 2005, Microtectonics).

Slickenlines: [Geometry] Scratches or linear markings on a slickenside that indicate slip direction along the slickenside. Also known as striae (singular stria). (Passchier and Trouw, 2005, Microtectonics).

Slickenside: Smoothed or polished, often grooved fault surface. Term usually used in plural form. Grooves may be indicative of the direction of fault movement.

Slip: [Mechanism] Displacement along a fault or crystallographic plane.

Slip plane: [Mechanism] Crystallographic plane along which a dislocation can move. (Passchier and Trouw, 2005, Microtectonics)"

Slip system: Combination of crystallographic plane and direction in which a dislocation can move.

Softening: [Mechanism] Decreasing resistance to deformation, expressed as decreasing differential stress at constant strain rate, or increasing strain rate at constant differential stress.

Solution transfer: [Mechanism] Displacement of matter through an aqueous solution in a rock. This process is usually associated with pressure solution and precipitation. (Passchier and Trouw, 2005, Microtectonics).

Spin: [Mechanism] Rotational component of flow, more specifically the angular velocity of instantaneous stretching axes in an external reference frame.

Spiral Si-garnet: [Mechanism] Garnet with a spiral-shaped inclusion pattern (Si) in thin section. The three-dimensional shape may be more complex. The angle of apparent relative rotation between Si in the centre of the garnet and Se is less than 180°. (Passchier and Trouw, 2005, Microtectonics).

SPO: Abbreviation for shape preferred orientation.

Stair-stepping: [Geometry/mechanism] Two planes show stair-stepping if they are parallel to each other but offset across a porphyroclast. Stair-stepping is common in recrystallised wings around porphyroclasts and can be used to determine sense of shear. (Passchier and Trouw, 2005, Microtectonics).

Static_recrystallisation: [Mechanism] General term for recovery and grain boundary migration processes, driven by remaining dislocations and a large surface of grain boundaries, mainly after deformation. It involves GBAR and minor SGR- and GBM recrystallisation and recovery, and leads to removal of undulose extinction, straightening of grain boundaries and grain growth. (Passchier and Trouw, 2005, Microtectonics).

Strain: [Mechanism] Tensorial quantity describing change in shape; a strained situation is commonly represented as an ellipsoid, comparing with an unstrained situation represented by a sphere. Three principal stretches along the axes of the strain ellipsoid define the magnitude of three-dimensional strain. Strain is a more restricted term than deformation, which also includes rotational and translational components. (Passchier and Trouw, 2005, Microtectonics).

Strain cap: [Geometry] Strongly foliated domain adjacent to a rigid object, usually enriched in mica or insoluble minerals. Strain caps generally occur together with strain shadows; the former lie in the shortening direction and the latter in the extension direction around the object.

Strain ellipsoid: [Geometry] Representation of strain in three dimensions. A sphere with radius 1 deforms into a strain. (Passchier and Trouw, 2005, Microtectonics).

Strain free: Descriptive term for an optically undeformed looking crystal lattice, i.e. without undulose extinction and subgrains. A strain free grain may be undeformed, or have lost intracrystalline deformation features by recovery or recrystallisation. (Passchier and Trouw, 2005, Microtectonics).

Strain fringe: [Mechanism-Geometry] Type of strain shadow containing fibrous material precipitated adjacent to a stiff or rigid object. The fringe is usually composed of another mineral than the rigid object.

Strain hardening: [Mechanism] Hardening of a rock with increasing strain.

Strain shadow: [Geometry-mechanism] Cone-shaped domain adjacent to a porphyroclast or porphyroblast in the direction of the foliation and usually composed of another mineral than the porphyroclast or -blast. It forms by rearrangement of material in response to inhomogeneous deformation of the matrix adjacent to the porphyroclast or -blast. Strain shadows are usually massive or contain equidimensional crystals; if they contain fibres, the term strain fringe is used instead. A mantled porphyroclast differs from a strain shadow in that the mantle has the same mineral composition as the porphyroclast and is inferred to have formed at the expense of the porphyroclast by recrystallisation. (Passchier and Trouw, 2005, Microtectonics).

Strain softening: [Mechanism] Softening of a rock with increasing strain.

Stress: [Mechanism] Tensorial quantity with six independent variables describing the orientation and magnitude of force vectors acting on planes of any orientation at a specific point in a volume of rock. (Passchier and Trouw, 2005, Microtectonics).

Stretch: [Mechanism] Change in length of a line: new length, divided by original length.

Stretching fault: [Geometry] It is an active fault in a flowing rock body with two wall-rock blocks that are changing length in the slip direction while slip accumulates (Means, 1980). The South Tibetan Detachment in Southern Tibet (Himalayan range) is regarded as a regional-scale example of stretching fault.

Stretching lineation: [Mechanism-geometry] Object lineation defined by aggregates or deformed single grains inferred to have formed by stretching grains or grain aggregates.

Striae: Alternative term for slickenlines.

Strike-slip: [Geology/kinematic] Strike-slip system are faults that comprise straights, segments sub-parallel to the regional slip vector, and bends oblique to it. Displacements may be transferred between two faults across an offset. Pure strike-slip on the straights necessarily causes potential overlap at a bend of one sense (restraining bend, Crowell 1974) and a potential void at a bend of the other sense (releasing bend, Crowell 1974)[Woodcock and Fisher, 1986]. The component of the fault displacement parallel to the fault strike.

Structure: Geometrically distinct feature in a rock; if penetratively developed, it is known as a fabric element. (Passchier and Trouw, 2005, Microtectonics).

Stylolite: [Geology] Surface in a rock, commonly rich in insoluble material and of irregular shape, which formed by localised removal of material by pressure solution. In 3D the surface can carry many narrow teeth normal or oblique to the surface which gave the structure its name. From Latin stylus – pen, and Greek λιθος – stone"

Subgrain: [Geometry] Small regions within a grain with uniform extinction, but clearly related to other subgrains in orientation, which together make up a whole grain. The misorientation sufficient to declare that two regions are still subgrains is to say that the misorientation is less than 7 degrees, but this is impossible to measure using a standard microscope and stage. Forms by migration and accumulation of dislocations with the same sign. Often concentrated at grain edges at low temperatures.

Subhedral crystal: Crystal with irregular crystal form but with some well developed crystal faces (see also anhedral, euhedral and hypidiomorphic). (Passchier and Trouw, 2005, Microtectonics).

Subophitic microstructure: Common igneous fabric that consists of elongate plagioclase grains which are partly surrounded by pyroxene grains and partly in contact with other plagioclase grains. This microstructure is found in basaltic and gabbroic rocks. (Passchier and Trouw, 2005, Microtectonics).

Superfault: [Geometry/mechanism] Normal fault with exceptionally strong development of fault rocks, thought to have formed by a catastrophic event such as caldera collapse or meteorite impact. (Passchier and Trouw, 2005, Microtectonics).

Suture: Margin between two colliding continents.

Syntaxial fringe: [Geometry] Fringe in with the growth surface lies between the fringe and the matrix (see also crinoid type fringe).

Syntaxial vein: [Geometry] Vein with fibre growth from the walls towards the median line. (Microtectonics, Passchier and Trouw, 2005).

Taber growth: [Mechanism] Growth of fibres in a vein due to advection of material through a porous wall rock. Vein walls can be pushed apart by the growing fibres. (Passchier and Trouw, 2005, Microtectonics).

Tectonic event: Period of deformation recognisable over a large area, distinct and separable from earlier and later events. Tectonic events may correspond to one or more deformation phases.

Tectonics: [Geology] Treated as singular or plural Large-scale processes affecting the structure of the earth's crust. (Cambridge dictionary) Science of the structure of the earth's crust, and of the movements and forces which have produced it. (after Murawski, 1963). Structural setting of a particular area. (AAPG International Tectonic Dictionary, 1967).

Tectono-metamorphic discontinuity: [Geometry/metamorphism] The use of the term “tectono-metamorphic discontinuity” is intended to be comprehensive for both tectonic features (including ductile and/or brittle shear zones and related kinematic indicators) and detectable metamorphic differences between hanging-wall and footwall triggered by the discontinuity (Montomoli et al., 2013 Tectonophysics, http://www.sciencedirect.com/science/article/pii/S0040195113003636). One regional-scale example in the Himalayan belt is constituted by the Higher Himalayan Discontinuity in the Greater Himalayan Sequence, occurring for more than 700 km along strike (Montomoli et al., 2015 Geol. Soc. London SP. Publication, n. 412).

TEM: Abbreviation for transmission electron microscope.

Texture: Synonym for microfabric or microstructure in most geological literature. In the non-geological literature on metals and ceramics the term is used for lattice-preferred orientation. (Passchier and Trouw, 2005, Microtectonics).

Thermal ionization mass spectrometry: Method of mass spectrometry using ions that are produced by heating and ionising sample material.

Thermochronology: Thermochronology is a branch of the geochronology that record the thermal evolution of rocks revealed through the cooling ages obtained from a defined thermochronometers (e.g. zircon and apatite fission-track, (U-Th)/He apatite etc.).

Thermochronometer: A thermochronometer is characterized by a specific radioisotopic system that presents radioactive feature and the mineral where it is found[https://goo.gl/Hov5MZ].

Tiling: [Geometry] Structure of imbricate large grains, arranged as tiles on a roof; this structure may occur in igneous rocks with phenocrysts and in mylonites with porphyroclasts, and can be used to determine sense of shear. (Passchier and Trouw, 2005, Microtectonics).

TIMS: Abbreviation for Thermal Ionization Mass Spectrometry.

Tip Damage zone: Tip damage zone [kinematic and mechanical]: area of deformation formed in response to stress concentration at a fault tip (Fig. 5) (Kim et al., 2004); see also process zone. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Total strain: Complete finite strain undergone by a volume of rock from its origin as a sediment or igneous rock, including diagenetic strain. (Passchier and Trouw, 2005, Microtectonics).

Trace lineation: [Mechanism/geometry] Lineation formed by parallel arrangement of linear features without volume, such as fold axes or intersection lines. (Passchier and Trouw, 2005, Microtectonics).

Trailing: [geometric and kinematic] Where two new faults or other types of fractures are connected via an older fault or other type of fracture, on which renewed displacement occurs to connect the two later faults or other types of fractures. Trailing faults are illustrated by Nixon et al. (2014) and trailing veins shown by Virgo et al. (2013, Fig. 12c). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Transfer fault: [kinematic] Fault that allows kinematic-linkage between two other faults, commonly at a high angle to those faults (e.g., Karson and Rona, 1990). (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Transgranular fracture: Relatively planar fracture crossing several grains. Passchier and Trouw, 2005.

Transposition: [Mechanism] Erasure of older fabric elements by strong deformation and/or metamorphic processes. (Passchier and Trouw, 2005, Microtectonics).

Transpression: [Tectonic-Mechanics] Transpression is considered as a transcurrent shear along a shear plane. Transpression occurs when both the horizontal shortening across and vertical lengthening along are coeval [http://www.sciencedirect.com/science/article/pii/0191814184900580]. The term has been used to describe strains of strike-slip structures formed during traspressional or transtesnional stress conditions (Marret and Peackock, 1999)."

Transtension: [Tectonic/Mechanism] Trastension is a strike-slip deformation that deviates from simple shear of a component of, respectively, shortening or extension orthogonal to the deformation zone [http://sp.lyellcollection.org/content/135/1/1].

Triple junction: [geological] Where three fracture traces at approximately 120° to each other meet at a point, commonly used for the boundaries of three tectonic plates (e.g., McKenzie and Morgan, 1969). Also see polygonal faults, cooling joints. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29).

Twinning: [Mechanics-kinematics] [Twinning] Is a deformation process that occurs while a mineral deforms in a specific crystallographic direction. Only a limited amount of strain can be accommodated by twinning and the process it is often coupled with pressure solution, dislocation creep or recrystallization. Common minerals where this process occurs are plagioclase and calcite but has been observed also in dolomite, kyanite, and microcline, biotite, quartz diopside and jadeite. Generally, twins are bounded by zoning and accumulate in the high strain rim of the crystal or between the contact of two crystals (Passchier and Trouw, 1989).

Twist wall: Type of subgrain boundary that consists of two intersecting sets of screw dislocations with different Burgers vectors. (Passchier and Trouw, 2005, Microtectonics).

Type I S-C_mylonite: other term for C/S fabric as found in mylonitised granites (Lister and Snoke 1984).

Type II S-C mylonite: Term mainly used for stair stepping wings around mica fish in quartzite mylonite, and interpreted as a type of C/S fabric (Lister and Snoke 1984).

Ultramylonite: Extremely fine-grained mylonite or mylonite with 90–100 vol-% matrix and 0–10 vol-% porphyroclasts. (Passchier and Trouw, 2005, Microtectonics).

Undulose extinction: [Mechanics] Undulose extinction appears as wavy extinction, common in quartz and calcite, due to plastic strain. The crystal lattice is actually bent so that when the microscope stage is rotated, one or more bands of extinction with gradational boundaries will sweep across the grain. Shows that the crystal is full of a distributed cloud dislocations [http://www.tectonique.net/mscourse2014/glossary/glossary1.html]."

Vacancy: Point defect in a crystal lattice; a missing lattice.

Veins: [Geological] As we all know (Bonz et al, 1999; Uri et al., 1999) veins are caused by infilling of mud cracks in shallow lakes with snail shells and snake bones, which recrystallize to form thin calcite-rich tabular bodies. A relatively thin, normally tabular, rock mass of distinctive lithologic character, cross-cutting the structure of the host rock. (AAPG International Tectonic Dictionary 1967).

Vorticity: Rotational component of flow, measured as themean angular velocity of material lines with respect to ISA. (Passchier and Trouw, 2005, Microtectonics)"

Wings: [Geometry] Term used for the appendages present on both sides of porphyroclasts trending parallel to the foliation. Sometimes referred to as “tails”.

X-, Y- and Z-axes: Principal strain axes. X is the maximum, Y the intermediate and Z the minimum stretch. (Passchier and Trouw, 2005, Microtectonics).

Xenoblast: A mineral or aggregate of minerals which has grown during metamorphism without that the grain boundary is regulated by its characteristic crystal faces [http://www.tectonique.net/mscourse2014/glossary/glossary4.html#idiobastic]. Also Known as allotrioblast.

X-node: [topological] The intersection point between two crossing faults or other types of fractures, with the traces thereby forming an X pattern (Fig. 2) (Manzocchi, 2002; Sanderson and Nixon, 2015). They are rare in fault networks due to the difficulty in preservation with increased displacements (Nixon et al., 2012). See topology, node, connecting. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Yield stress: Differential stress value, above which a material starts to deform permanently. Below the yield stress deformation is elastic. Since stress and elasticity are tensors, the yield stress is not a single number in most materials. (Passchier and Trouw, 2005, Microtectonics).

Y-node: [topological] Where one fault or other type of fracture ends at another fault or other type of fracture, with the traces thereby forming a Y pattern (Fig. 2). Such a geometric relationship can be produced in a number of ways including splaying, abutting and cross-cutting relationships (Manzocchi, 2002; Sanderson and Nixon, 2015). See topology, node, connecting node. (From Peacock et al., 2016, Glossary of fault and other fracture networks, J. Structural, Geology, 92, 12-29)."

Zener pinning: Pinning of grain boundaries on small solid inclusions, thus inhibiting grain growth. (Passchier and Trouw, 2005).