Geology and Minerals

Flat slab subduction

Flat slab subduction is a tectonic plate structure in which a continental plate sits above a subducted plate (a slab) sliding beneath it with a low subduction angle (<30 degrees to horizontal) beyond the seismogenic layer, and a resumption of normal subduction far from the trench. In a broader sense, the term may include any shallowly dipping lower plate, as in western Mexico. Flat slab subduction is associated with the pinching out of the asthenosphere under the plates, an inland migration of arc magmatic eruption (magmatic sweep), and an eventual cessation of arc magmatism. The coupling of the flat slab to the upper plate is thought to change the style of deformation occurring on the upper plate's surface and form basement-cored uplifts like the Rocky Mountains. The flat slab also may hydrate the lower continental lithosphere and be involved in the formation of economically important ore deposits. During the subduction, a flat slab itself may deform or buckle, causing sedimentary hiatus in marine sediments on the slab. The failure of a flat slab is associated with ignimbritic volcanism and the reverse migration of arc volcanism. Multiple working hypotheses about the cause of flat slabs are subduction of thick, buoyant oceanic crust (15–20 km) and trench rollback accompanying a rapidly overriding upper plate and enhanced trench suction. The west coast of South America has two of the largest flat slab subduction zones. Flat slab subduction is occurring at 10% of subduction zones.

Also on this shelf

See also

• ▸Ductility (Earth science)
• ▸Cooper State Park
• ▸Galeras tragedy

Uncatalogued shelf

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