Suture (geology)

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A suture is in structural geology a major fault zone through an orogen or mountain range. Sutures separate terranes: tectonic units that have different plate tectonic, metamorphic and paleogeographic histories.

[edit] Overview

Before the two units were thrust over each other a piece of crust was in between, that is not or only fragmentarily found back. In plate tectonics sutures are seen as the remains of subduction zones, the two terranes are then interpreted as fragments of different palaeocontinents or tectonic plates.

Outcropping sutures can differ in width from a few hundred meters to a couple of kilometers. They can be networks of mylonitic shear zones, brittle fault zones but usually both. Sutures are usually associated with igneous intrusions and tectonic lenses of all kind of lithologies, from plutonic rocks to ophiolitic fragments.

The word suture when referring to geology can also refer to the suture line, a division on a trilobite between the free check and the fixed cheek; this suture line allowed the trilobite to perform ecdysis (the shedding of its skin).

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