Melt evolution above a spontaneously retreating subducting slab in a three-dimensional model

Zhu, Guizhi; Gerya, Taras; Yuen, David A.

doi:10.1007/s12583-011-0165-x

Cited by 7 publications

(4 citation statements)

References 34 publications

(36 reference statements)

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“…All model boundaries are free slip, except for the lower one that is permeable. More detailed information about numerical modelling approach and material properties are given in Zhu et al 28 and Supplementary Table S2. An oceanic geotherm 29 defines the initial temperature field of the oceanic plates.…”

Section: Methodsmentioning

confidence: 99%

Oblique subduction modelling indicates along-trench tectonic transport of sediments

et al. 2013

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Convergent plate margins are currently distinguished as 'accretional' or 'erosional', depending on the tendency to accumulate sediments, or not, at the trench. Accretion and erosion can coexist along the same margin and we have noticed that this mostly occurs where subduction is oblique. Here we show that at oblique subduction zones, sediments that enter the trench are first buried, and later migrate laterally parallel to the trench and at various depths. Lateral migration of sediments continues until they reach a physical barrier where they begin to accumulate. The accretionary wedge size decreases along the trench moving away from the barrier. We therefore suggest that the gradual variation of the accretionary wedge size and sediment amount at the trench along one single subduction zone, as observed in many active plate margins worldwide, can be explained by the lateral tectonic migration of sediments driven by obliquity of subduction as well.

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Section: Methodsmentioning

confidence: 99%

Oblique subduction modelling indicates along-trench tectonic transport of sediments

et al. 2013

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“…Although foundering is probably an important mechanism in some places [ DeBari and Sleep , ; Kelemen et al ., ], recent studies have shown that felsic material may also detach from the slab because of the intrinsic buoyancy of the sediment layer itself [ Currie et al ., , Behn et al ., , Hacker et al ., ; Miller and Behn , ] and hence modify the sub‐arc mantle. Alternatively, hydration and partial melting atop the slab may trigger the formation of composite diapirs composed of partially molten basalt, sediment, and hydrated/serpentinized mantle [ Gerya and Yuen , ; Gerya et al ., ; Gerya and Meilick , ; Zhu et al ., , Zhu et al ., , ; Vogt et al ., ]. Some of these latter studies were examined using laboratory experiments in terms of major element compositions and phase relations [ Castro and Gerya , , Castro et al ., ; Castro et al ., ; Castro et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of geochemical variations caused by crustal relamination

Vogt

Castro

Gerya

2013

Geochem Geophys Geosyst

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[1] Geochemical consequences of composite diapirs formed in subduction zones have been studied using a thermomechanical numerical model of an ocean-continent subduction zone. This model includes dehydration of subducted crust, aqueous fluid transport, partial melting, and melt emplacement. Subduction of crustal material to sublithospheric depth results in the formation of a tectonic rock mélange composed of basalt, sediment, and hydrated /serpentinized mantle. At asthenospheric depth, this rock mélange may evolve into partially molten diapirs and rise through the mantle prior to emplacement (relamination) at crustal levels. We have investigated the composition and the geochemical evolution of liquids derived from such composite diapirs by analyzing the differing proportions of the crustal end-members in the source, i.e., basalt and sediment. Our results show that the proportions of the components (in the diapiric mélange) are limited to short-range variations within an interval of X b [=volume fraction of basalt/(basalt + sediment)] = 0.4 À 0.8, yielding melt with a relatively stable granodioritic major element composition. Hence, granodioritic melt is transported by rising composite diapirs to crustal levels, contributing to the growth of the continental crust. In addition to this, we have calculated Sr and Nd isotopic initial ratios of the diapiric mélange as a function of time, based on the fraction of the components in the mélange. Liquids derived from composite diapirs inherit the geochemical characteristics of the composite source and show distinct temporal variations of radiogenic isotopes depending on the changing values of X b . Partial melting of composite diapirs is therefore expected to produce melt with a constant major element composition but substantial changes in terms of radiogenic isotopes.

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“…They proposed that preexisting cracks and fissures in initially homogeneous oceanic crust are important factors for clustering of the arc volcanoes. Our initial model with a homogeneous oceanic crust without preexisting cracks and fissures can also produce volcanoes in clusters due to spontaneous clustering of dehydration and melting processes above the slabs driven by water‐induced buoyancy in the mantle wedge [e.g., Zhu et al ., , , ; Honda et al ., ]. That means, preexisting cracks are not a prerequisite for volcanic clustering when we take into account the role of fluid in the subduction zone.…”

Section: Discussionmentioning

confidence: 65%

“…England and Katz [] argued that the arc is located above the place where the boundary defined by the anhydrous solidus makes its closest approach to the trench. In this study, we analyze 3‐D variations in the concentration of mobile water and water release rate in the subduction zone, which reflect the path and source of the fluids/melts in the mantle wedge [e.g., Zhu et al ., ]. Profiles of the mobile water concentration and water release rate for the reference model “Rvp65” and the slow‐subduction‐velocity model “Rvp2” are shown in the fourth and fifth columns of Figures and , respectively.…”

Section: Resultsmentioning

confidence: 99%

Four‐dimensional numerical modeling of crustal growth at active continental margins

et al. 2013

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[1] Crustal growth and topography development in subduction-related arcs are intimately related to magmatic processes and melt production above subducting slabs. Lateral and temporal variations in crustal thickness and composition have been observed in nature, but until now no integrated approach has been developed to comprehensively understand magmatic activity in subduction-related arcs. Here we investigate the 4-D spatial, temporal, and compositional character of continental crustal growth at active margins using a new 4-D (space-time) petrological-thermomechanical numerical model of a subduction-related magmatic arc. Based on a series of numerical experiments, we demonstrate that crustal growth inside the arc is inherently clustered in both space and time. The characteristic wavelength of variations in crustal thickness and topography along the arc is on the order of 30-80 km and is comparable to volcano clustering in natural arcs. The clusters of new crust are formed mainly by basaltic melt episodically extracted from partially molten peridotite due to lateral variation of water release and transport in the mantle wedge. Melts derived from subducted oceanic crust and sediments could contribute up to 15-50 vol% to the arc crust growth and their relative proportion is maximal at the onset of subduction. The total amount of newly formed crust correlates mainly with the amount of convergence since the beginning of subduction and is not strongly influenced by the plate convergence velocity. Indeed, slower subduction and lower melt extraction efficiency helps partially molten sediments and oceanic crust to be transported into the mantle wedge by hydrated, partially molten diapiric structures. For the modeled regime of stable subduction, the maximum crustal additional rate (25-40 km 3 /km/Myr) occurs when the amount of convergence reaches around 700 km. Mantle wedge structures developed in our models correlate well with available geophysical (seismological) observations for the Alaskan subduction zone. In particular, partially molten mantle plumes found in our models could explain low seismic anomalies in the mantle wedge, whereas mobile water and water release patterns could reflect paths and sources for magmatic activity evidenced by seismic b-value and Vp/Vs ratio analysis.

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Melt evolution above a spontaneously retreating subducting slab in a three-dimensional model

Abstract: Dehydration of the subducting slab favors the melting of the surrounding mantle. Water content and melt evolution atop a spontaneously retreating subducting slab are reported in a three-

Cited by 7 publications

References 34 publications

Oblique subduction modelling indicates along-trench tectonic transport of sediments

Oblique subduction modelling indicates along-trench tectonic transport of sediments

Numerical modeling of geochemical variations caused by crustal relamination

Four‐dimensional numerical modeling of crustal growth at active continental margins

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