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 ?
The foliated peridotite has also been called as tectonite or ultramafic tectonite (Ahmad and Abbas, 1979; Siddiqui et al.
The results are generally in keeping with earlier analyses, with metamorphic grains including tectonite and quartzite.
Counts presented in Table 2 present a similar composition to Coarse Utility Ware sherds, with a near absence of plagioclase but a higher metamorphic lithic count, also including quartzite and tectonite.
Interestingly, detailed inspection of the orientation distribution of crystal directions and planes with respect to the tectonite reference system (foliation and lineation) allows us to discuss the activity of different mechanisms during deformation (e.
Magnetic fabric and quantitative texture analysis using Time-of-flight neutron diffraction: Examples in tectonites (NW Iberian Massif, Spain)
The mineral composition of tectonites which developed under metamorphic conditions in the crust is dominated by feldspars, quartz, amphiboles and sheet silicates.
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.
Most of the time, all of them are strongly serpentinized, so that, macroscopically, they appear as a mass of fractured soapstone; only in one occasion, on a boulder of Puerto Nuevo beach, which appears at low tide, their real structure of a strongly folded tectonite could have been appreciated.
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.
Lithic fragments include chert, siltstone, sandstone, phylite, schist, metasandstone, quartz-mica tectonites, quartz-mica aggregates and pelitic shale.