Evidence of oceanic plate delamination in the Northern Atlantic

Abstract The Earth’s surface is constantly being recycled by plate tectonics. Subduction of oceanic lithosphere and delamination of continental lithosphere constitute the two most important mechanisms by which the Earth’s lithosphere is recycled into the mantle. Delamination or detachment in continental regions typically occurs below mountain belts due to a weight excess of overthickened lithospheric mantle, which detaches from overlying lighter crust, aided by the existence of weak layers within the continental lithosphere. Oceanic lithosphere is classically pictured as a rigid plate with a strong core that does not allow for delamination to occur. Here, we propose that active delamination of oceanic lithosphere occurs offshore Southwest Iberia. The process is assisted by the existence of a lithospheric serpentinized layer that allows the lower part of the lithosphere to decouple from the overlying crust. Tomography images reveal a sub-lithospheric high-velocity anomaly below this region, which we interpret as a delaminating block of old oceanic lithosphere. We present numerical models showing that for a geological setting mimicking offshore Southwest Iberia delamination of oceanic lithosphere is possible and may herald subduction initiation, which is a long-unsolved problem in the theory of plate tectonics. We further propose that such oceanic delamination is responsible for the highest-magnitude earthquakes in Europe, including the M8.5-8.7 Great Lisbon Earthquake of 1755 and the M7.9 San Vincente earthquake of 1969. In particular, our numerical models, in combination with calculations on seismic potential, provide a solution for the instrumentally recorded 1969 event below the flat Horseshoe abyssal plain, away from mapped tectonics faults. Delamination of old oceanic lithosphere near passive margins constitutes a new class of subduction initiation mechanisms, with fundamental implications for the dynamics of the Wilson cycle.

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Forced subduction initiation at passive continental margins: Numerical modeling

10.5194/egusphere-egu2020-1761 ◽

2020 ◽

Author(s):

Xinyi Zhong ◽

Zhong-Hai Li

Keyword(s):

Subduction Zones ◽

Plate Tectonics ◽

Numerical Models ◽

Oceanic Lithosphere ◽

Ocean Basin ◽

Passive Margin ◽

Complex Case ◽

Subduction Initiation ◽

Boundary Force ◽

Time Required

Subduction initiation (SI) induced by the tectonic boundary force may play a significant role in the Wilson cycle. In the previous analog and numerical models, the constant convergent velocity is generally applied, which may lead to large boundary forces for SI. In this study, we begin with testing the simple case of SI at passive margin with constant convergent force. The results indicate that the boundary force required to trigger the SI at passive margin with a thin and young oceanic lithosphere is much lower than that with a thick and old one. It is consistent with the multiple Cenozoic subduction zones in the Southwest Pacific, which are young ocean basin within 40 Ma and compressed by the India-Australia plate. Furthermore, we extended our model to explore a more complex case, forced SI during the collision-induced subduction transference, which is critical for Tethyan evolution. Both collision and SI processes are integrated in the numerical models. The results indicate that the forced convergence, rather than pure free subduction, is required to trigger and sustain the SI in the neighboring passive margin after collision of terrane. In addition, a weak passive margin can significantly promote the occurrence of subduction initiation, by decreasing required boundary force within reasonable range of plate tectonics. However, the lengths of subducted oceanic slab and accreting terrane play secondary roles in the occurrence of SI after collision. Under the favorable conditions of collision-induced subduction transference, the time required for subduction initiation after collision is generally within 10 Myrs, which is consistent with the general geological records of Neo-Tethys. In contrast, both Atlantic passive margin and Indian passive margin are old and stable with absence of subduction initiation in the present, which remains an open question.

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Lateral propagation–induced subduction initiation at passive continental margins controlled by preexisting lithospheric weakness

Science Advances ◽

10.1126/sciadv.aaz1048 ◽

2020 ◽

Vol 6 (10) ◽

pp. eaaz1048 ◽

Cited By ~ 3

Author(s):

Xin Zhou ◽

Zhong-Hai Li ◽

Taras V. Gerya ◽

Robert J. Stern

Keyword(s):

Subduction Zones ◽

Plate Tectonics ◽

Numerical Models ◽

Three Dimensional ◽

Passive Margin ◽

Continental Margins ◽

Subduction Initiation ◽

Passive Margins ◽

The North ◽

Lateral Propagation

Understanding the conditions for forming new subduction zones at passive continental margins is important for understanding plate tectonics and the Wilson cycle. Previous models of subduction initiation (SI) at passive margins generally ignore effects due to the lateral transition from oceanic to continental lithosphere. Here, we use three-dimensional numerical models to study the possibility of propagating convergent plate margins from preexisting intraoceanic subduction zones along passive margins [subduction propagation (SP)]. Three possible regimes are achieved: (i) subducting slab tearing along a STEP fault, (ii) lateral propagation–induced SI at passive margin, and (iii) aborted SI with slab break-off. Passive margin SP requires a significant preexisting lithospheric weakness and a strong slab pull from neighboring subduction zones. The Atlantic passive margin to the north of Lesser Antilles could experience SP if it has a notable lithospheric weakness. In contrast, the Scotia subduction zone in the Southern Atlantic will most likely not propagate laterally.

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The role of Edge-Driven Convection in the generation of volcanism I: a 2D systematic study

10.5194/se-2020-120 ◽

2020 ◽

Author(s):

Antonio Manjón-Cabeza Córdoba ◽

Maxim Ballmer

Keyword(s):

Numerical Models ◽

High Volume ◽

Oceanic Lithosphere ◽

Companion Paper ◽

Small Scale ◽

Continental Lithosphere ◽

Transient Phenomenon ◽

Mantle Viscosity ◽

Wide Range

Abstract. The origin of intraplate volcanism is not explained by the plate tectonic theory, and several models have been put forward for explanation. One of these models involves Edge-Driven Convection (EDC), in which cold and thick continental lithosphere is juxtaposed to warm and thin oceanic lithosphere to trigger convective instability. To test whether EDC can produce long-lived high-volume magmatism, we run numerical models of EDC for a wide range of mantle properties and edge (i.e., the oceanic-continental transition) geometries. We find that the most important parameters that govern EDC are the rheological paramaters mantle viscosity η0 and activation energy Ea. However, even the maximum melting volumes found in our models are insufficient to account for island-building volcanism on old seafloor, such as at the Canary Islands and Cape Verde. Also, beneath old seafloor, localized EDC-related melting commonly transitions into widespread melting due to small-scale sublithospheric convection, inconsistent with the distribution of volcanism at these volcanic chains. In turn, EDC is a good candidate to sustain the formation of small seamounts on young seafloor, as it is a highly transient phenomenon that occurs in all our models soon after initiation. In a companion paper, we investigate the implications of interaction of EDC with mantle-plume activity.

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EVIDENCE OF MANTLE INHERITANCE ON THE ULTRA-DISTAL WESTERN IBERIAN MARGIN FROM TRANSFORMED TOTAL MAGNETIC ANOMALY

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v36i3.1957 ◽

2018 ◽

Vol 36 (3) ◽

pp. 1 ◽

Cited By ~ 2

Author(s):

Luizemara Soares Alves Szameitat ◽

Francisco José Fonseca Ferreira ◽

Gianreto Manatschal ◽

Monica da Costa Pereira Lavalle Helbron

Keyword(s):

Steady State ◽

Magnetic Anomaly ◽

Oceanic Crust ◽

Oceanic Lithosphere ◽

Magnetic Data ◽

Continental Lithosphere ◽

Flow Lines ◽

Passive Margins ◽

Magnetic Features ◽

Iberian Margin

ABSTRACT. Inheritance on continental lithosphere is considered as an important aspect on passive margins, since they may control magmatic budget and strain evolution during rifting and lithospheric breakup. On the distal Western Iberian margin, the transition to a steady state oceanic crust was little sampled and less investigated, in comparison to the more proximal parts near to the continental edge. In this work, we use marine magnetic data to analyze some aspects of the transition between the zone of exhumed continental mantle (ZECM) and the unequivocal oceanic crust, using transformed magnetic data. We observe that the end of the ZECM presents some straight magnetic features, especially at the eastern limit of the J anomaly. These magnetic lineaments are consistent with Early Cretaceous flow lines of the Iberian Plate. Straight structures are not expected in a newly formed oceanic lithosphere. Instead, it seems to be controlled by mantle inheritance. These straight magnetic features may indicate basement inheritance controlling magmatic insertions at the beginning of the oceanic crust formation.Keywords: Iberia, Magnetometry, Ocean-Continent Transition, Inherited Structures, Magma-Poor Margin. RESUMO. Estruturas herdadas na litosfera continental são um aspecto importante em margens passivas, pois poderão condicionar a entrada de magma e a evolução da deformação durante o rifteamento e quebra litosférica. Na porção distal da Margem Ibérica Ocidental, a transição da crosta continental até a crosta oceânica bem estabelecida possui menos dados e é menos investigada em comparação com a porção junto do limite de crosta continental. Neste trabalho, usamos dados magnéticos marinhos para analisar alguns aspectos entre a zona de exumação mantélica e a crosta oceânica inequívoca, através de dados magnéticos transformados. Observa-se que o final da zona de exumação mantélica apresenta algumas feições retilíneas, especialmente no limite leste da Anomalia J. Estes lineamentos magnéticos estão em conformidade com linhas de fluxo mesozoicas da Placa Ibérica. Feições retilíneas não são esperadas em uma litosfera oceânica neoformada. Ao contrário, estas aparentam ser um controle dado por estruturas pretéritas do manto. Portanto, estas feições magnéticas retilíneas sugerem uma herança do embasamento continental controlando as intrusões magmáticas no início da formação da crosta oceânica.Palavras-chave: Ibéria, Magnetometria, Transição Continente-Oceano, Estruturas Herdadas, Margem Pobre em Magma.

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Boninitic blueschists record subduction initiation and subsequent accretion of an arc–forearc in the northeast Proto-Tethys Ocean

Geology ◽

10.1130/g49457.1 ◽

2021 ◽

Cited By ~ 1

Author(s):

Dong Fu ◽

Bo Huang ◽

Tim E. Johnson ◽

Simon A. Wilde ◽

Fred Jourdan ◽

...

Keyword(s):

Subduction Zones ◽

Plate Tectonics ◽

Oceanic Lithosphere ◽

Island Arc ◽

Early Paleozoic ◽

Subduction Initiation ◽

North Qilian Orogenic Belt ◽

Mariana Arc ◽

Tethys Ocean ◽

North Qilian

Subduction of oceanic lithosphere is a diagnostic characteristic of plate tectonics. However, the geodynamic processes from initiation to termination of subduction zones remain enigmatic mainly due to the scarcity of appropriate rock records. We report the first discovery of early Paleozoic boninitic blueschists and associated greenschists from the eastern Proto-Tethyan North Qilian orogenic belt, northeastern Tibet, which have geochemical affinities that are typical of forearc boninites and island arc basalts, respectively. The boninitic protoliths of the blueschists record intra-oceanic subduction initiation at ca. 492–488 Ma in the eastern North Qilian arc/forearc–backarc system, whereas peak blueschist facies metamorphism reflects subsequent subduction of the arc/forearc complex to high pressure at ca. 455 Ma. These relations therefore record the life circle of an intra-oceanic subduction zone within the northeastern Proto-Tethys Ocean. The geodynamic evolution provides an early Paleozoic analogue of the early development of the Izu–Bonin–Mariana arc and its later subduction beneath the extant Japanese arc margin. This finding highlights the important role of subduction of former upper plate island arc/forearcs in reducing the likelihood of preservation of initial subduction-related rock records in ancient orogenic belts.

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The future of Earth's oceans: consequences of subduction initiation in the Atlantic and implications for supercontinent formation

Geological Magazine ◽

10.1017/s0016756816000716 ◽

2016 ◽

Vol 155 (1) ◽

pp. 45-58 ◽

Cited By ~ 15

Author(s):

JOÃO C. DUARTE ◽

WOUTER P. SCHELLART ◽

FILIPE M. ROSAS

Keyword(s):

Atlantic Ocean ◽

Conceptual Model ◽

Subduction Zone ◽

Subduction Zones ◽

Plate Tectonics ◽

Turning Point ◽

Oceanic Lithosphere ◽

Subduction Initiation ◽

The Pacific ◽

The Future

AbstractSubduction initiation is a cornerstone in the edifice of plate tectonics. It marks the turning point of the Earth's Wilson cycles and ultimately the supercycles as well. In this paper, we explore the consequences of subduction zone invasion in the Atlantic Ocean, following recent discoveries at the SW Iberia margin. We discuss a buoyancy argument based on the premise that old oceanic lithosphere is unstable for supporting large basins, implying that it must be removed in subduction zones. As a consequence, we propose a new conceptual model in which both the Pacific and the Atlantic oceans close simultaneously, leading to the termination of the present Earth's supercycle and to the formation of a new supercontinent, which we name Aurica. Our new conceptual model also provides insights into supercontinent formation and destruction (supercycles) proposed for past geological times (e.g. Pangaea, Rodinia, Columbia, Kenorland).

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The subduction initiation stage of the Wilson cycle

Geological Society London Special Publications ◽

10.1144/sp470.3 ◽

2018 ◽

Vol 470 (1) ◽

pp. 415-437 ◽

Cited By ~ 17

Author(s):

Robert Hall

Keyword(s):

Subduction Zones ◽

Plate Tectonics ◽

Oceanic Lithosphere ◽

The West ◽

Subduction Initiation ◽

Deep Crust ◽

Close Relationship ◽

Wilson Cycle ◽

Initiation Stage ◽

Time Required

AbstractIn the Wilson cycle, there is a change from an opening to a closing ocean when subduction begins. Subduction initiation is commonly identified as a major problem in plate tectonics and is said to be nowhere observable, yet there are many young subduction zones at the west Pacific margins and in eastern Indonesia. Few studies have considered these examples. Banda subduction developed by the eastwards propagation of the Java trench into an oceanic embayment by tearing along a former ocean–continent boundary. The earlier subducted slab provided the driving force to drag down unsubducted oceanic lithosphere. Although this process may be common, it does not account for young subduction zones near Sulawesi at different stages of development. Subduction began there at the edges of ocean basins, not at former spreading centres or transforms. It initiated at a point where there were major differences in elevation between the ocean floor and the adjacent hot, weak and thickened arc/continental crust. The age of the ocean crust appears to be unimportant. A close relationship with extension is marked by the dramatic elevation of land, the exhumation of deep crust and the spectacular subsidence of basins, raising questions about the time required to move from no subduction to active subduction, and how initiation can be identified in the geological record.

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Accretionary orogenesis in the Lake Superior region, USA: modern-like tectonics during the Paleoproterozoic

10.5194/egusphere-egu2020-21104 ◽

2020 ◽

Author(s):

Daniel R. Viete ◽

Robert M. Holder

Keyword(s):

Plate Tectonics ◽

Lake Superior ◽

Oceanic Lithosphere ◽

Ocean Basin ◽

Length Scale ◽

Subduction Initiation ◽

Suprasubduction Zone ◽

Lithospheric Extension ◽

Rapid Switching ◽

Terrane Accretion

Terrane accretion and tectonothermal activity associated with the Penokean and Yavapai Orogenies are recorded in various geologic elements of the Lake Superior region, USA, including: (1) mafic&#8211;ultramafic terranes comprising tholeiitic basalts and gabbros, boninites and calc-alkaline volcanics and intrusives (e.g., the Pembine&#8211;Wausau Terrane), and (2) multiple and distinct, short-length-scale (5&#8211;15 km) chlorite&#8211;biotite&#8211;garnet&#8211;staurolite&#8211;(kyanite&#8211;)sillimanite regional metamorphic isograd sequences. These geologic associations reflect development of a suprasubduction zone system (subduction initiation?) within a Paleoproterozoic ocean in the Orosirian Period, followed by episodes of short-duration (limited-length-scale) tectonometamorphism during accretionary orogenesis in the Statherian Period.The geologic processes recorded in the Paleoproterozoic terranes of the Lake Superior region are very common in the Phanerozoic. We suggest that Paleoproterozoic tectonism in the Lake Superior region may reflect a West Pacific-type setting, involving distinct, short-lived tectonothermal events marking periods of subduction rollback and lithospheric extension, punctuated by episodes of arc/microcontinent collision, terrane accretion and lithospheric shortening.The apparent operation of modern-like plate tectonics&#8212;accretionary tectonics involving rapid switching between lithospheric extension and shortening&#8212;in the Paleoproterozoic requires that a scenario of temporally-varying buoyancy forces at the subduction zone (spatially-varying density of the subducting slab?) be reconciled with the thicker (slower-densifying) oceanic lithosphere expected for a hotter Earth. Such a scenario may be explained by: (1) an anomalously cool mantle (producing anomalously thin oceanic crust) beneath the ocean basin whose closure led to the accretionary orogenesis recorded in the Lake Superior region, or (2) an incredibly long-lived (>> 100 Myr) ocean basin that allowed widespread development of critically-overdense lithosphere prior to subduction initiation and onset of accretionary orogenesis associated with the Penokean and Yavapai Orogenies.We are currently investigating geologic associations in the Lake Superior region and their potential tectonic origins, using whole-rock geochemistry to test for the tectonic origins of the Pembine&#8211;Wausau Terrane, and 40Ar/39Ar geochronology/geospeedometry to constrain time scales for the tectonometamorphism that produced the metamorphic isograd sequence in the region of Republic, Michigan. Results will provide new insights into accretionary tectonics during the Paleoproterozoic, and processes controlling the emergence and evolution of plate tectonics on Earth.

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Vertically Driven Dynamics and Magmatism of Rapid Subduction Initiation in the Western Pacific

10.5194/egusphere-egu2020-19611 ◽

2020 ◽

Author(s):

Ben Maunder ◽

Saskia Goes ◽

Julie Prytulak ◽

Mark Reagan

Keyword(s):

Plate Tectonics ◽

Numerical Models ◽

Plate Boundaries ◽

Temporal And Spatial Distribution ◽

Subduction Initiation ◽

Primary Driver ◽

International Ocean Discovery Program ◽

Subduction System ◽

The Western Pacific

Plate tectonics requires the formation of plate boundaries. Particularly important is the enigmatic initiation of subduction: the sliding of one plate below the other, and the primary driver of plate tectonics. A continuous, in situ record of subduction initiation was recovered by the International Ocean Discovery Program Expedition 352, which drilled a segment of the fore-arc of the Izu-Bonin-Mariana subduction system, revealing a distinct magmatic progression with a rapid timescale (approximately 1 million years). Here, using numerical models, we demonstrate that these observations cannot be produced by previously proposed horizontal external forcing. Instead a geodynamic evolution that is dominated by internal, vertical forces produces both the temporal and spatial distribution of magmatic products, and progresses to self-sustained subduction. Such a primarily internally driven initiation event is necessarily whole-plate scale and the rock sequence generated (also found along the Tethyan margin) may be considered as a smoking gun for this type of event.

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Plume-induced subduction initiation: single- or multi-slab subduction?

10.5194/egusphere-egu2020-7783 ◽

2020 ◽

Author(s):

Marzieh Baes ◽

Stephan Sobolev ◽

Taras Gerya ◽

Sascha Brune

Keyword(s):

Mantle Plume ◽

Subduction Zones ◽

Plate Tectonics ◽

Large Scale ◽

Oceanic Lithosphere ◽

Extension Rate ◽

Subduction Initiation ◽

Lithospheric Extension ◽

Mechanical Models ◽

Mantle Temperature

The formation of new subduction zones is a key component of global plate tectonics. Initiation of subduction following the impingement of a hot buoyant mantle plume is one of the few scenarios that allow breaking the lithosphere and recycling a stagnant lid without requiring any pre-existing weak zones. According to this scenario, upon arrival of a hot and buoyant mantle plume beneath the lithosphere, the lithosphere breaks apart and the hot mantle plume materials flow atop of the broken parts of the lithosphere. This leads to bending of the lithosphere and eventually initiation of subduction. Plume-lithosphere interaction can lead to subduction initiation provided that the plume causes a critical local weakening of the lithospheric material above it, which depends on the plume volume, its buoyancy, and the thickness of the lithosphere. Previous modeling studies showed that plume-lithosphere interaction can result in initiation of multi- or single-slab subduction zones around the newly formed plateau. However, they did not explore the parameters playing key roles in discriminating between the single- and multi-slab subduction scenarios. Here, we investigate factors controlling the number and shape of retreating subducting slabs formed by plume-lithosphere interaction. Using 3d thermo-mechanical models we show that the response of the lithosphere to arrival of a mantle plume beneath it depends on several parameters such as age of oceanic lithosphere, thickness of the crust, large-scale lithospheric extension rate, relative location of plume head and plateau edge and mantle temperature. The numerical experiments reveal that plume-lithosphere interaction in present day Earth can result in three different deformation regimes: (a) multi-slab subduction initiation, (b) single-slab subduction initiation and (c) plateau formation without subduction initiation. On early Earth (in Archean times) plume-lithosphere interaction could result in formation of either multi-slab subduction zones, very efficient in production of new crust, or episodic short-lived circular subduction. Extension eases subduction initiation caused by plume-lithosphere interaction. Plume-induced subduction initiation of old oceanic lithosphere with a plateau with thick crust is only possible if the lithosphere is subjected to extension.

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