Slab (geology)

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The figure is a schematic diagram depicting a subduction zone. The subduction slab on the right enters the mantle with a varying temperature gradient while importing water in a downward motion. Cross-section of a subduction zone and back-arc basin.jpg
The figure is a schematic diagram depicting a subduction zone. The subduction slab on the right enters the mantle with a varying temperature gradient while importing water in a downward motion.
A model of the subducting Farallon Slab under North America Farallon Plate.jpg
A model of the subducting Farallon Slab under North America

In geology, the slab is a significant constituent of subduction zones. [1]

Subduction slabs drive plate tectonics by pulling along the lithosphere to which they attach in a process known as slab pull and by inducing currents in the mantle via slab suction. [2] The slab affects the convection and evolution of the Earth's mantle due to the insertion of the hydrous oceanic lithosphere. [3] Dense oceanic lithosphere retreats into the Earth's mantle, while lightweight continental lithospheric material produces active continental margins and volcanic arcs, generating volcanism. [4] Recycling the subducted slab presents volcanism by flux melting from the mantle wedge. [5] The slab motion can cause dynamic uplift and subsidence of the Earth's surface, forming shallow seaways [2] and potentially rearranging drainage patterns. [6]

Geologic features of the subsurface can infer subducted slabs by seismic imaging. [7] [8] Subduction slabs are dynamic; slab characteristics such as slab temperature evolution, flat-slab, deep-slab, and slab detachment can be expressed globally near subduction zones. [9] Temperature gradients of subducted slabs depend on the oceanic plate's time and thermal structures. [10] Slabs experiencing low angle (less than 30 degrees) subduction is considered flat-slab, primarily in southern China and the western United States. [11] [12] Marianas Trench is an example of a deep slab, thereby creating the deepest trench in the world established by a steep slab angle. [13] Slab breakoff occurs during a collision between oceanic and continental lithosphere, [14] allowing for a slab tear; an example of slab breakoff occurs within the Himalayan subduction zone. [4]

See also

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<span class="mw-page-title-main">Oceanic trench</span> Long and narrow depressions of the sea floor

Oceanic trenches are prominent, long, narrow topographic depressions of the ocean floor. They are typically 50 to 100 kilometers wide and 3 to 4 km below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about 50,000 km (31,000 mi) of oceanic trenches worldwide, mostly around the Pacific Ocean, but also in the eastern Indian Ocean and a few other locations. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of 10,994 m (36,070 ft) below sea level.

<span class="mw-page-title-main">Lithosphere</span> Outermost shell of a terrestrial-type planet or natural satellite

A lithosphere is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy.

<span class="mw-page-title-main">Subduction</span> A geological process at convergent tectonic plate boundaries where one plate moves under the other

Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the heavier plate dives beneath the second plate and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with rates of convergence as high as 11 cm/year.

<span class="mw-page-title-main">Convergent boundary</span> Region of active deformation between colliding tectonic plates

A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.

<span class="mw-page-title-main">Island arc</span> Arc-shaped archipelago formed by intense seismic activity of long chains of active volcanoes

Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone. They are the principal way by which continental growth is achieved.

<span class="mw-page-title-main">Volcanic arc</span> Chain of volcanoes formed above a subducting plate

A volcanic arc is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc located further from the subducting plate than the trench. The oceanic plate is saturated with water, mostly in the form of hydrous minerals such as micas, amphiboles, and serpentines. As the oceanic plate is subducted, it is subjected to increasing pressure and temperature with increasing depth. The heat and pressure break down the hydrous minerals in the plate, releasing water into the overlying mantle. Volatiles such as water drastically lower the melting point of the mantle, causing some of the mantle to melt and form magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.

<span class="mw-page-title-main">Izanagi Plate</span> Ancient tectonic plate

The Izanagi Plate was an ancient tectonic plate, which began subducting beneath the Okhotsk Plate 130–100 Ma. The rapid plate motion of the Izanagi Plate caused northwest Japan and the outer zone of southwest Japan to drift northward. High-pressure metamorphic rocks were formed at the eastern margin of the drifting land mass in the Sanbagawa metamorphic belt, while low-pressure metamorphic rocks were formed at its western margin in the Abukuma metamorphic belt. At approximately 55 Ma, the Izanagi Plate was completely subducted and replaced by the western Pacific Plate, which also subducted in a northwestern direction. Subduction-related magmatism took place near the Ryoke belt. No marked tectonics occurred in the Abukuma belt after the change of the subducted plate.

<span class="mw-page-title-main">Back-arc basin</span> Submarine features associated with island arcs and subduction zones

A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of them result from tensional forces, caused by a process known as oceanic trench rollback, where a subduction zone moves towards the subducting plate. Back-arc basins were initially an unexpected phenomenon in plate tectonics, as convergent boundaries were expected to universally be zones of compression. However, in 1970, Dan Karig published a model of back-arc basins consistent with plate tectonics.

<span class="mw-page-title-main">Hikurangi Plateau</span> A large igneous province and subsurface plateau in the Pacific Ocean

The Hikurangi Plateau is an oceanic plateau in the South Pacific Ocean east of the North Island of New Zealand. It is part of a large igneous province (LIP) together with Manihiki and Ontong Java, now located 3,000 km (1,900 mi) and 3,500 km (2,200 mi) north of Hikurangi respectively. Mount Hikurangi, in Māori mythology the first part of the North Island to emerge from the ocean, gave its name to the plateau.

Slab pull is a geophysical mechanism whereby the cooling and subsequent densifying of a subducting tectonic plate produces a downward force along the rest of the plate. In 1975 Forsyth and Uyeda used the inverse theory method to show that, of the many forces likely to be driving plate motion, slab pull was the strongest. 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. The ridge push at rifts contributes only 5 to 10%.

<span class="mw-page-title-main">Back-arc region</span>

The back-arc region is the area behind a volcanic arc. In island volcanic arcs, it consists of back-arc basins of oceanic crust with abyssal depths, which may be separated by remnant arcs, similar to island arcs. In continental arcs, the back-arc region is part of the continental platform, either dry land (subaerial) or forming shallow marine basins.

<span class="mw-page-title-main">Crustal recycling</span> Tectonic recycling process

Crustal recycling is a tectonic process by which surface material from the lithosphere is recycled into the mantle by subduction erosion or delamination. 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 is proof of crustal recycling.

A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin. The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops. The magmatism and petrogenesis of continental crust are complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.

<span class="mw-page-title-main">Flat slab subduction</span> Subduction characterized by a low subduction angle

Flat slab subduction is characterized by a low subduction angle beyond the seismogenic layer and a resumption of normal subduction far from the trench. A slab refers to the subducting lower plate. A broader definition of flat slab subduction includes any shallowly dipping lower plate, as in western Mexico. Flat slab subduction is associated with the pinching out of the asthenosphere, an inland migration of arc magmatism, 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.

<span class="mw-page-title-main">Subduction polarity reversal</span>

Subduction polarity reversal is a geologic process in which two converging plates switch roles: The over-lying plate becomes the down-going plate, and vice versa. There are two basic units which make up a subduction zone. This consists of an overriding plate and the subduction plate. Two plates move towards each other due to tectonic forces. The overriding plate will be on the top of the subducting plate. This type of tectonic interaction is found at many plate boundaries.

<span class="mw-page-title-main">Slab detachment</span> Process occurring in plate tectonics

In plate tectonics, slab detachment or slab break-off may occur during continent-continent or arc-continent collisions. When the continental margin of the subducting plate reaches the oceanic trench of the subduction zone, the more buoyant continental crust will in normal circumstances experience only a limited amount of subduction into the asthenosphere. The slab pull forces will, however, still be present and this normally leads to the breaking off or detachment of the descending slab from the rest of the plate. The isostatic response to the detachment of the downgoing slab is rapid uplift. Slab detachment is also followed by the upwelling of relatively hot asthenosphere to fill the gap created, leading in many cases to magmatism.

<span class="mw-page-title-main">Kevin C. A. Burke</span> British geologist (1929–2018)

Kevin C. A. Burke was a geologist known for his contributions in the theory of plate tectonics. In the course of his life, Burke held multiple professorships, most recent of which (1983-2018) was the position of professor of geology and tectonics at the Department of Earth and Atmospheric Science, University of Houston. His studies on plate tectonics, deep mantle processes, sedimentology, erosion, soil formation and other topics extended over several decades and influenced multiple generations of geologists and geophysicists around the world.

<span class="mw-page-title-main">Earth system interactions across mountain belts</span>

Earth system interactions across mountain belts are interactions between processes occurring in the different systems or "spheres" of the Earth, as these influence and respond to each other through time. Earth system interactions involve processes occurring at the atomic to planetary scale which create linear and non-linear feedback(s) involving multiple Earth systems. This complexity makes modelling Earth system interactions difficult because it can be unclear how processes of different scales within the Earth interact to produce larger scale processes which collectively represent the dynamics of the Earth as an intricate interactive adaptive system.

<span class="mw-page-title-main">Mariana mud volcanoes</span>

Mud volcanoes in the Mariana fore-arc are a hydrothermal geologic landform that erupt slurries of mud, water, and gas. There are at least 10 mud volcanoes in the Mariana fore-arc that are actively erupting, including the recently studied Conical, Yinazao, Fantagisna, Asut Tesoro, and South Chamorro serpentinite mud volcanoes. These mud volcanoes erupt a unique serpentinite mud composition that is related to the geologic setting in which they have formed. Serpentinite mud is the product of mantle metasomatism due to subduction zone metamorphism and slab dehydration. As a result, the serpentinite mud that erupts from these mud volcanoes often contains pieces of mantle peridotite material that has not fully altered during the serpentinization process. In addition to pieces of altered mantle material, pieces of subducted seamounts have also been found within the serpentinite muds. Serpentinite mud volcanoes in the Mariana fore-arc are often located above faults in the fore-arc crust. These faults act as conduits for the hydrated mantle material to ascend towards the surface. The Mariana mud volcanoes provide a direct window into the process of mantle hydration that leads to the production of arc magmas and volcanic eruptions.

<span class="mw-page-title-main">Oblique subduction</span> Tectonic process

Oblique subduction is a form of subduction for which the convergence direction differs from 90° to the plate boundary. Most convergent boundaries involve oblique subduction, particularly in the Ring of Fire including the Ryukyu, Aleutian, Central America and Chile subduction zones. In general, the obliquity angle is between 15° and 30°. Subduction zones with high obliquity angles include Sunda trench and Ryukyu arc.

References

  1. Conrad, C. P. "How Mantle Slabs Drive Plate Motions". Archived from the original on June 13, 2011. Retrieved 24 April 2011.
  2. 1 2 Mitrovica, J. X.; Beaumont, C.; Jarvis, G. T. (1989). "Tilting of continental interiors by the dynamical effects of subduction". Tectonics. 8 (5): 1079. Bibcode:1989Tecto...8.1079M. doi:10.1029/TC008i005p01079.
  3. Wada, Ikuko; Behn, Mark D.; Shaw, Alison M. (2012-11-01). "Effects of heterogeneous hydration in the incoming plate, slab rehydration, and mantle wedge hydration on slab-derived H2O flux in subduction zones". Earth and Planetary Science Letters. 353–354: 60–71. Bibcode:2012E&PSL.353...60W. doi:10.1016/j.epsl.2012.07.025. ISSN   0012-821X.
  4. 1 2 Frisch, Wolfgang; Meschede, Martin; Blakey, Ronald (2011), "Subduction zones, island arcs and active continental margins", Plate Tectonics, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 91–122, doi:10.1007/978-3-540-76504-2_7, ISBN   978-3-540-76503-5 , retrieved 2021-12-10
  5. Iwamori, Hikaru (1998-07-01). "Transportation of H2O and melting in subduction zones". Earth and Planetary Science Letters. 160 (1): 65–80. Bibcode:1998E&PSL.160...65I. doi:10.1016/S0012-821X(98)00080-6. ISSN   0012-821X.
  6. Shephard, G. E.; Müller, R. D.; Liu, L.; Gurnis, M. (2010). "Miocene drainage reversal of the Amazon River driven by plate–mantle interaction". Nature Geoscience. 3 (12): 870–75. Bibcode:2010NatGe...3..870S. CiteSeerX   10.1.1.653.4596 . doi:10.1038/ngeo1017.
  7. Rondenay, Stéphane; Abers, Geoffrey A.; van Keken, Peter E. (2008). "Seismic imaging of subduction zone metamorphism". Geology. 36 (4): 275. Bibcode:2008Geo....36..275R. doi:10.1130/G24112A.1. ISSN   0091-7613.
  8. Zhao, Dapeng; Ohtani, Eiji (2009-12-01). "Deep slab subduction and dehydration and their geodynamic consequences: Evidence from seismology and mineral physics". Gondwana Research. 16 (3): 401–413. Bibcode:2009GondR..16..401Z. doi:10.1016/j.gr.2009.01.005. ISSN   1342-937X.
  9. Hu, Jiashun; Gurnis, Michael (April 2020). "Subduction Duration and Slab Dip". Geochemistry, Geophysics, Geosystems. 21 (4). Bibcode:2020GGG....2108862H. doi: 10.1029/2019GC008862 . ISSN   1525-2027. S2CID   216305697.
  10. Holt, A. F.; Condit, C. B. (June 2021). "Slab Temperature Evolution Over the Lifetime of a Subduction Zone". Geochemistry, Geophysics, Geosystems. 22 (6). Bibcode:2021GGG....2209476H. doi:10.1029/2020GC009476. ISSN   1525-2027. S2CID   232378621.
  11. Schellart, Wouter Pieter (2020). "Control of Subduction Zone Age and Size on Flat Slab Subduction". Frontiers in Earth Science. 8: 26. Bibcode:2020FrEaS...8...26S. doi: 10.3389/feart.2020.00026 . ISSN   2296-6463.
  12. Liu, Xiaowen; Currie, Claire A. (2019). "Influence of Upper Plate Structure on Flat-Slab Depth: Numerical Modeling of Subduction Dynamics". Journal of Geophysical Research: Solid Earth. 124 (12): 13150–13167. Bibcode:2019JGRB..12413150L. doi:10.1029/2019JB018653. ISSN   2169-9356. S2CID   210254422.
  13. Gvirtzman, Zohar; Stern, Robert J. (April 2004). "Bathymetry of Mariana trench-arc system and formation of the Challenger Deep as a consequence of weak plate coupling". Tectonics. 23 (2): n/a. Bibcode:2004Tecto..23.2011G. doi: 10.1029/2003tc001581 . ISSN   0278-7407. S2CID   21354196.
  14. Huw Davies, J.; von Blanckenburg, Friedhelm (1995-01-01). "Slab breakoff: A model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens". Earth and Planetary Science Letters. 129 (1): 85–102. Bibcode:1995E&PSL.129...85D. doi:10.1016/0012-821X(94)00237-S. ISSN   0012-821X.