Peeling oceanic crust in subduction zones

Kimura, Gaku; Ludden, John

doi:10.1130/0091-7613(1995)023<0217:pocisz>2.3.co;2

Cited by 149 publications

(98 citation statements)

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“…In this type of accretion, the FAT crust does not subduct completely, but instead builds out the accretionary wedge seaward, as in an accretionary plate margin (Clift and Vannucchi, 2004). Landward-verging imbricate thrust faults typically shear off blocks of tens to hundreds of meters of FAT or oceanic crust (Kimura and Ludden, 1995). For example, the Oso Melange and Oso Igneous Complex in Costa Rica records the history of accreted oceanic plateaus, island arcs, and seamounts which were mixed in with accretionary prism sediments (Buchs et al, 2009).…”

Section: Accretionary Orogenesis Processesmentioning

confidence: 99%

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Tetreault

Buiter

2014

Solid Earth

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Abstract. Allochthonous accreted terranes are exotic geologic units that originated from anomalous crustal regions on a subducting oceanic plate and were transferred to the overriding plate by accretionary processes during subduction. The geographical regions that eventually become accreted allochthonous terranes include island arcs, oceanic plateaus, submarine ridges, seamounts, continental fragments, and microcontinents. These future allochthonous terranes (FATs) contribute to continental crustal growth, subduction dynamics, and crustal recycling in the mantle. We present a review of modern FATs and their accreted counterparts based on available geological, seismic, and gravity studies and discuss their crustal structure, geological origin, and bulk crustal density. Island arcs have an average crustal thickness of 26 km, average bulk crustal density of 2.79 g cm −3 , and three distinct crustal units overlying a crust-mantle transition zone. Oceanic plateaus and submarine ridges have an average crustal thickness of 21 km and average bulk crustal density of 2.84 g cm −3 . Continental fragments presently on the ocean floor have an average crustal thickness of 25 km and bulk crustal density of 2.81 g cm −3 . Accreted allochthonous terranes can be compared to these crustal compilations to better understand which units of crust are accreted or subducted. In general, most accreted terranes are thin crustal units sheared off of FATs and added onto the accretionary prism, with thicknesses on the order of hundreds of meters to a few kilometers. However, many island arcs, oceanic plateaus, and submarine ridges were sheared off in the subduction interface and underplated onto the overlying continent. Other times we find evidence of terrane-continent collision leaving behind accreted terranes 25-40 km thick. We posit that rheologically weak crustal layers or shear zones that were formed when the FATs were produced can be activated as detachments during subduction, allowing parts of the FAT crust to accrete and others to subduct. In many modern FATs on the ocean floor, a sub-crustal layer of high seismic velocities, interpreted as ultramafic material, could serve as a detachment or delaminate during subduction.

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Section: Accretionary Orogenesis Processesmentioning

confidence: 99%

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Tetreault

Buiter

2014

Solid Earth

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“…As a result, the uppermost oceanic crust, which is mainly made up of basaltic rock, is eventually directly exposed to the upper plate of the lithified accretionary prism. This eventuality can be explained by duplex underplating due to "décollement step-down" into the ocean-plate basalts, as exemplified by several ancient accretionary prisms (Silver et al 1985;Kimura and Mukai 1991;Kimura and Ludden 1995). Paleothermal analyses (Matsumura et al 2003;Ikesawa et al 2005) and seismic reflection surveys of the modern accretionary margin in the Nankai Trough, southwest Japan (Park et al 2002), suggest that the site where décollement step-down is initiated almost coincides with the up-dip boundary of the seismogenic zone where great earthquakes repeatedly occur (normally defined as having a temperature range of ~100-150 to ~350 °C; Hyndman 2007).…”

Section: Introductionmentioning

confidence: 99%

Alteration and dehydration of subducting oceanic crust within subduction zones: implications for décollement step-down and plate-boundary seismogenesis

Kameda

Inoué

Tanikawa

et al. 2017

Earth Planets Space

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The alteration and dehydration of predominantly basaltic subducting oceanic crustal material are thought to be important controls on the mechanical and hydrological properties of the seismogenic plate interface below accretionary prisms. This study focuses on pillow basalts exposed in an ancient accretionary complex within the Shimanto Belt of southwest Japan and provides new quantitative data that provide insight into clay mineral reactions and the associated dehydration of underthrust basalts. Whole-rock and clay-fraction X-ray diffraction analyses indicate that the progressive conversion of saponite to chlorite proceeds under an almost constant bulk-rock mineral assemblage. These clay mineral reactions may persist to deep crustal levels (~320 °C), possibly contributing to the bulk dehydration of the basalt and supplying fluid to plate-boundary fault systems. This dehydration can also cause fluid pressurization at certain horizons within hydrous basalt sequences, eventually leading to fracturing and subsequent underplating of upper basement rock into the overriding accretionary prism. This dehydration-induced breakage of the basalt can explain variations in the thickness of accreted basalt fragments within accretionary prisms as well as the reported geochemical compositions of mineralized veins associated with exposed basalts in onland locations. This fracturing of intact basalt can also nucleate seismic rupturing that would subsequently propagate along seismogenic plate interfaces.© The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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“…The phyllites, however, most likely formed during shallow level underplating of continental detritus beneath the offscraped distal turbidites (Figure 11). The associated incipient blueschist facies metabasite strip was peeled off from the sinking oceanic crust and mixed tectonically with the phyllites during underplating along the basal décollement (Kimura and Ludden, 1995).…”

Section: Discussionmentioning

confidence: 99%

“…Tectonic frontal accretion is achieved by mainly scraping off trenchfill turbidites as imbricated packages and underplating them along the basal décollement beneath the offscraped part of the wedge (Karig and Sharman, 1975;Platt, 1986;Sample and Fischer, 1986;Kimura and Ludden, 1995). The wedges can reach several hundred kilometers in width at active continental margins when there is a high amount of sediment supply into trench, as in the Makran (e.g., Platt et al, 1985;McCall, 2002).…”

Section: Introductionmentioning

confidence: 99%

Thermal structure of low-grade accreted Lower Cretaceous distal turbidites, the Central Pontides, Turkey: insights for tectonic thickening of an accretionary wedge

Aygül¹,

Okay²,

Oberhänsli³

et al. 2015

Turkish J Earth Sci

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Albian-Turonian subduction-accretionary complexes are exposed widely in the Central Pontides. A major portion of the accretionary complexes is made up of a metaflysch sequence consisting of slate/phyllite and metasandstone intercalation with blocks of marble, Na-amphibole bearing metabasite, and serpentinite. The metaflysch sequence represents distal parts of a large Lower Cretaceous submarine turbidite fan deposited on the Laurasian active continental margin that was subsequently accreted and metamorphosed during the Albian. Raman spectra of carbonaceous material of the metapelitic rocks revealed that the metaflysch consists of metamorphic packets with distinct peak metamorphic temperatures. The majority of the metapelites are low-temperature (ca. 330°C) slates characterized by lack of differentiation of the graphite (G) and D2 defect bands. They possibly represent offscraped distal turbidites along the toe of the Albian accretionary wedge. Other phyllites are characterized by a slightly pronounced G band with a D2 defect band occurring on its shoulder. Peak metamorphic temperatures of these phyllites are constrained to 370-385 °C. The phyllites are associated with a strip of incipient blueschist facies metabasites and are found as a sliver within the offscraped distal turbidites. We interpret the phyllites as underplated continental sediments together with oceanic crustal basalt along the basal décollement. Tectonic emplacement of the underplated rocks into the offscraped distal turbidites was possibly achieved by out-of-sequence thrusting causing tectonic thickening and uplift of the wedge.

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Peeling oceanic crust in subduction zones

Cited by 149 publications

References 0 publications

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Alteration and dehydration of subducting oceanic crust within subduction zones: implications for décollement step-down and plate-boundary seismogenesis

Thermal structure of low-grade accreted Lower Cretaceous distal turbidites, the Central Pontides, Turkey: insights for tectonic thickening of an accretionary wedge

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