Tectonite


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tectonite

[′tek·tə‚nīt]
(petrology)
A rock in which the history of its deformation is reflected in its fabric.

Tectonite

 

a rock in which the minerals have acquired a certain orientation under the action of deep-seated forces of the earth. This action is usually accompanied by recrystallization, the formation of foliation, or comminuation (as in mylonites and tectonic breccias). The study of tectonites through structural analysis (seePETROTECTONICS) permits determination of (1) the orientation of the compressive and shearing stresses acting during dynamic metamorphism and (2) the later stages of deformation.

Three groups of tectonites are distinguished according to the nature of mineral orientation. The groups reflect types of differential movement of matter. In the first case, platy minerals, such as mica, are arranged parallel to glide planes so as to produce cleavage. In the second case, the gliding in the minerals occurs along two intersecting planes. The third case is characterized by the rotation of grains around axes that are usually oriented along the trends of folds.

REFERENCE

Azhgirei, G. D. Strukturnaia geologiia [2nd ed.]. Moscow, 1966.

P. N. KROPOTKIN

References in periodicals archive ?
It shows a tectonite structure with both small and large particles, and these particles are bound to each other with calcite cement.
The foliated peridotite has also been called as tectonite or ultramafic tectonite (Ahmad and Abbas, 1979; Siddiqui et al., 1996).
The results are generally in keeping with earlier analyses, with metamorphic grains including tectonite and quartzite.
1), comprises gabbro, pyroxenite, and relatively homogeneous harzburgites (mantle tectonite?).
Sherd Sherd Sherd Grain Surface A7 (#1) A22a (#1) type (1) (#1) Quartz 22 25 22 Plagioclase 9 10 10 K-feldspar 1 1 2 (orthoclase) Opaque 2 2 2 (iron oxide) Chalcedony 3 2 2 (chert) Quartz-mica 1 1 1 tectonite (slate) Glassy VRF 55 53 53 Felsitic VRF 3 3 4 Microlitic VRF 4 3 4 Total VRF (62) (59) (61) Grain Average Standard type (1) (n=3) deviation (2) Quartz 23 2.1-2.2 Plagioclase 10 1.4-1.5 K-feldspar l 0.5-0.7 (orthoclase) Opaque 2 0.7 (iron oxide) Chalcedony 2 0.7-0.9 (chert) Quartz-mica 1 0.5 tectonite (slate) Glassy VRF 54 ~2.5 FelsiticVRF 3 0.9-1.0 Microlitic VRF 4 0.9-1.0 Total VRF (61) (~2.5) (1) VRF = volcanic rock fragments.
Carranza et al., "REE geochemistry of altered tectonites in the Huize base-metal district, Yunnan, China," Geochemistry: Exploration, Environment, Analysis, vol.
melanges) and metamorphic tectonites, and coincides with termination of the last phase of arc magmatism (ca.
It shows a collisional heft at the easternmost part of the Sierras Pampeanas, with a series of mafic and ultramafic rocks associated with tectonites. In this area, a magmatic arc developed during most of the cycle (Ramos and Vujovich, 1993).