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Tag: Fluid release

3-D subduction mantle flow

3-D subduction dynamics and mantle flow model animation showing the time evolution of oceanic plate subduction and resulting mantle flow.

Animation of 3-D subduction dynamics and mantle flow showing the time evolution of oceanic plate subduction with a continental part in the middle and resulting mantle flow computed in a 3-D numerical model. Although only one specific geometry, this model is useful to visualise how slabs deform at depth, how mantle flows around their edges, and how back-arc basins form.

Description of the model evolution (see below for detailed legend) – In this model, the subducting plate is mostly oceanic, but has continental lithosphere in the middle and the overriding plate is continental (see top panels at Time 0 Myr). The oceanic slab (in blue) sinks into the mantle and, at Time 8.1 Myr, continental collision happens in the middle of the subduction zone. At this point, the trench stays quasi-stationary in the middle, but starts to retreat quickly at the sides and the slab significantly deforms at depth (from Time 9.8 Myr onward). This causes the mantle to quickly flow around the slab (see how the spheres move). The large trench retreat generates a significant amount of extension in the overriding plate that eventually causes the overriding plate to break (Time 28.4 Myr). At this point, the mantle material rises towards the surface and starts melting because of decompression in the back-arc region. Melt close to trench is due to the presence of fluids released from the slab and shows the location of the volcanic arc. As the slab keeps retreating, the opening of the back-arc basin, associated with mantle melting, continues creating a wider and wider basin that will be composed of new oceanic crust generated by mantle melting.

Legend – The 3 panels are showing different views of the same model: side/top view (top left panel), top view (top right panel), and front view (bottom panel). The slab is shown in blue, continental crust in grey. In the top view (top right panel), the subducting plate is on the left side and the overriding plate is the grey area to the left. The slab will subduct towards the right. The contour in the red-to-white colour map indicates the regions where the mantle melts and the amount of melt fraction. The spheres are tracers passively transported in the mantle and colour-coded by depth; they are useful to show how the mantle flows around the slab (toroidal flow).

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Volcanic arc creation

A conceptual view of a volcanic arc growing through the evolution of magmatism in subduction zones controlled by fluid and melt fluxes.

A series of schematic cartoons (both as still and animated images) to show how a volcanic arc grows through the evolution of magmatism in subduction zones controlled by fluid and melt fluxes.

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Deep geologic water cycle

A schematic cartoon of the deep water cycle in the Earth’s mantle.

A schematic cartoon of the deep water cycle. Water percolates through the oceanic tectonic plates at the surface, hydrating the oceanic crust and lithospheric mantle below it. When the oceanic plates subduct, part of the water is released at shallow depths (<250 km) into the mantle wedge above the slab. This triggers mantle melting and the formation of volcanic arcs at the surface, in the overriding plate. The rest of the water stays in the slab and is carried deep down into the mantle. Depending on the subduction dynamics, this water can either be released at the mantle transition zone (410-660 km), where large amount of water can be stored in nominally anhydrous minerals, or go even deeper, up to the core-mantle boundary. Part of the water present in the mantle can then be released at the surface again by melt at intraplate volcanoes and mid-ocean ridges as it is transported by plumes and mantle convection.

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SZI geologic evidence

Schematic illustration of the emplacement of subduction zone initiation (SZI)-typical rock evidence during SZI, and a typical SZI ophiolite sequence.

Schematic illustration of the emplacement of subduction zone initiation (SZI)-typical rock evidence during SZI, and a typical SZI ophiolite sequence. Note that this is a text-book example (according to e.g., the Izu-Bonin-Mariana SZI) and that pre-existing structures (e.g., a pre-existing volcanic arc) or variable SZI dynamics (e.g., horizontal compression) could inhibit various stages and therefore their typical rock signatures.

  • Creator: Fabio Crameri
  • This version: 18.08.2021
  • License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
  • Specific citation: This graphic by Fabio Crameri from Crameri et al. (2020) is available via the open-access s-Ink repository.
  • Related reference: Crameri, F., V. Magni, M. Domeier, G.E. Shephard, K. Chotalia, G. Cooper, C. Eakin, A.G. Grima, D. Gürer, A. Király, E. Mulyukova, K. Peters, B. Robert, and M. Thielmann (2020), A transdisciplinary and community-driven database to unravel subduction zone initiation, Nature Communications, 11, 3750. doi:10.1038/s41467-020-17522-9
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