Shear (geology) - Shear Zone

Shear Zone

A shear zone is a tabular to sheetlike, planar or curviplanar zone composed of rocks that are more highly strained than rocks adjacent to the zone. Typically this is a type of fault but it may be difficult to place a distinct fault plane into the shear zone. Shear zones may form zones of much more intense foliation, deformation, and folding. En echelon veins or fractures may be observed within shear zones.

Many shear zones host ore deposits as they are a focus for hydrothermal flow through orogenic belts. They may often show some form of retrograde metamorphism from a peak metamorphic assemblage and are commonly metasomatised.

Shear zones can be only inches wide, or up to several kilometres wide. Often, due to their structural control and presence at the edges of tectonic blocks, shear zones are mappable units and form important discontinuities to separate terranes. As such, many large and long shear zones are named, identical to fault systems.

When the horizontal displacement of this faulting can be measured in the tens or hundreds of kilometers of length, the fault is referred to as a megashear. Megashears often indicate the edges of ancient tectonic plates.

Read more about this topic:  Shear (geology)

Other articles related to "shear zone, zone, shear zones, zones":

Lineation (geology) - Stretching Lineations
... This is parallel with the direction at which a shear zone or shearing force is stretching the rock ... stretched by movement along a ductile shear zone within which this outcrop resides ... The spherical conglomerate pebbles stretched along the direction of movement of this shear zone, attaining their current somewhat flattened cigar-shaped form ...
Cameroon Line - Geology - Surrounding Plate
... The Central African Shear Zone (CASZ), a lineament that extends from the Sudan to coastal Cameroon, runs under the continental section of the Cameroon line ... It is visible in the Foumban Shear Zone, which was active before and during the opening of the South Atlantic in the Cretaceous period ... The western end of the shear zone is obscured by the volcanoes of the Cameroon line, but based on reconstruction of the configuration of South America before it separated from Africa, the ...
Shear (geology) - Shear Zone
... A shear zone is a tabular to sheetlike, planar or curviplanar zone composed of rocks that are more highly strained than rocks adjacent to the zone ... this is a type of fault but it may be difficult to place a distinct fault plane into the shear zone ... Shear zones may form zones of much more intense foliation, deformation, and folding ...
Shear Zone - Importance
... The importance of shear zones lies in the fact that they are major zones of weakness in the Earth's crust, sometimes extending into the upper mantle ... Shear zones can host economically viable mineralizations, examples being important gold deposits in Precambrian terranes ...

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