What is a subduction slab?

Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth’s mantle at convergent boundaries. Once initiated, stable subduction is driven mostly by the negative buoyancy of the dense subducting lithosphere. The slab sinks into the mantle largely under its weight.

What does a slab do at a subduction zone?

Gaps within a subducting plate can alter the surrounding mantle flow field and the overall subduction zone dynamics by allowing hot sub-slab mantle to flow through the gaps and into the mantle wedge.

What is slab pull and subduction?

Slab pull is that part of the motion of a tectonic plate caused by its subduction. Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at oceanic trenches. This force and slab suction account for almost all of the force driving plate tectonics.

What causes flat slab subduction?

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. Flat slab subduction is occurring at 10% of subduction zones.

What happens to the flat slab during subduction?

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 be deformed, or buckling, causing sedimentary hiatus in marine sediments on the slab.

How does the lower plate sink in a subduction zone?

In many cases it’s more like jiu-jitsu: the lower plate is actively sinking as the bend along its front edge works backward (slab rollback), so that the upper plate is actually sucked over the lower plate. This explains why there are often zones of stretching, or crustal extension, in the upper plate at subduction zones.

How is the shape of the subduction zone constrained?

The shape of the flat slab is constrained through earthquakes within the subducting slab and the interface between the upper plate and the subducting slab. Flat slab zones along the Andean margin release 3-5 times more energy through upper plate earthquakes than adjacent, more steeply dipping subduction zones.

How are subducting slabs proof of crustal recycling?

The subducting slabs carry volatile compounds and water into the mantle, as well as crustal material with an isotopic signature different from that of primitive mantle. Identification of this crustal signature in mantle-derived rocks (such as mid-ocean ridge basalts or kimberlites) is proof of crustal recycling.