scholarly journals Earthquakes track subduction fluids from slab source to mantle wedge sink

2019 ◽  
Vol 5 (4) ◽  
pp. eaav7369 ◽  
Author(s):  
Felix Halpaap ◽  
Stéphane Rondenay ◽  
Alexander Perrin ◽  
Saskia Goes ◽  
Lars Ottemöller ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Mantle Wedge ◽  
Plate Interface ◽  
Earth’S Mantle ◽  
Nucleation Sites ◽  
Fluid Supply ◽  
Subduction Fluids ◽  
Geodynamic Models ◽  
Western Greece ◽  
Source And Sink

Subducting plates release fluids as they plunge into Earth’s mantle and occasionally rupture to produce intraslab earthquakes. It is debated whether fluids and earthquakes are directly related. By combining seismic observations and geodynamic models from western Greece, and comparing across other subduction zones, we find that earthquakes effectively track the flow of fluids from their slab source at >80 km depth to their sink at shallow (<40 km) depth. Between source and sink, the fluids flow updip under a sealed plate interface, facilitating intraslab earthquakes. In some locations, the seal breaks and fluids escape through vents into the mantle wedge, thereby reducing the fluid supply and seismicity updip in the slab. The vents themselves may represent nucleation sites for larger damaging earthquakes.

The Fate of Subduction Fluids above the Subduction Interface: Implications for Mantle Wedge Deformation Processes

2020 ◽  
Author(s):  
Samuel Angiboust ◽  
Johannes Glodny ◽  
Aitor Cambeses ◽  
Tom Raimondo ◽  
Patrick Monié ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Hanging Wall ◽  
Plate Interface ◽  
Rock Interaction ◽  
Multi Scale ◽  
Hp Metamorphism ◽  
Elastic Loading ◽  
Deformation Processes ◽  
Subduction Fluids ◽  
Shed Light

&lt;p&gt;The physical and mechanical processes rooted in the hydrated, serpentinized mantle above subduction zones (the &amp;#8220;cold nose&amp;#8221;) remain debated and poorly understood, despite fundamental consequences on the elastic loading of the seismogenic interface. The fluids crossing this interface are expected to generate nests of seismicity and at the same time weaken the interface hanging wall through serpentinization and metasomatic processes. Ultramafic and jadeitite samples from two natural laboratories where such fossil settings are now visible at the Earth&amp;#8217;s surface are used here to document multi-scale deformation mechanisms and fluid-rock interaction processes. Field relationships enable tracking the pathways followed by the fluids during HP metamorphism. Petrographic, geochemical, geochronological and microstructural observations demonstrate the complex interplay between brittle and plastic deformation processes throughout the gradual hydration of the cold nose mantle over millions of years. Changes in bulk rock geochemical and paragenetic sequence also reveal the evolution of the composition of the fluid source through time. These results shed light on the geometry of the cold nose above the interface, with implications for volatile budget estimates, rheology of the plate interface (including the various types of seismicity) as well as the interpretation of Vp/Vs ratios from active subduction settings worldwide.&lt;/p&gt;

scholarly journals The effect of obliquity on temperature in subduction zones: insights from 3D numerical modeling

2018 ◽  
Author(s):  
Alexis Plunder ◽  
Cédric Thieulot ◽  
Douwe J. J. van Hinsbergen
Keyword(s):  
Subduction Zones ◽  
Mantle Wedge ◽  
Numerical Models ◽  
Mantle Flow ◽  
Mathematical Function ◽  
3D Numerical Modeling ◽  
Plate Interface ◽  
Geological Record ◽  
Parallel Component ◽  
Central Turkey

Abstract. In subduction zones the geotherm is thought to vary as a function of the subduction rate and the age of the subducting lithosphere. Along a single subduction zone the rate of subduction can strongly vary due to changes in the angle between the trench and the plate convergence vector, namely the subduction obliquity. We currently observe such a configuration all around the Pacific (e.g. Marianna, Chile, Aleutians). Subduction obliquity is also supposed in the geological record of Western and Central Turkey. In order to investigate this effect, we designed and computed simple thermo-kinematic finite element 3D numerical models. We prescribe the trench geometry by means of a simple mathematical function and compute the mantle flow in the mantle wedge only by solving the equation of mass and momentum conservation. We then solve the energy conservation equation until steady-state is reached. We analyse the results (i) in terms of mantle wedge flow with emphasis on the trench-parallel component and (ii) in terms of temperature along the plate interface by means of maps and depths-temperature path at the interface. We show that the effect of the trench curvature on the geotherm is substantial. A small obliquity yields a small but not negligible trench parallel mantle flow leading to differences of 50 °C along strike of the model. With increasing obliquity, the trench parallel component of the velocity consequently increases and the temperature variation can be as important as 200 °C along strike. This can even be larger with varying plate velocity. Finally, we discuss the implication of our simulations for the ubiquitous oblique systems that are observed on Earth, the limitation of our modeling approach and the significance for the geological record with an emphasis on the case study of Western and Central Turkey.

Petrologic and geochemical role of serpentinite in subduction zones and plate interface domains

2015 ◽  
Vol 37 ◽  
pp. 61-64
Author(s):  
Marco Scambelluri ◽  
Enrico Cannaò ◽  
Mattia Gilio ◽  
Marguerite Godard
Keyword(s):  
Subduction Zones ◽  
Plate Interface

Magmatic evidence for Late Carboniferous-Early Permian slab breakoff and extension of the southern Mongolia collage system in Central Asia

2021 ◽  
Author(s):  
Hai Zhou ◽  
Guochun Zhao ◽  
Donghai Zhang
Keyword(s):  
Subduction Zones ◽  
Volcanic Rocks ◽  
Early Carboniferous ◽  
Ocean Basin ◽  
Magma Source ◽  
Central Asian ◽  
Slab Rollback ◽  
Slab Breakoff ◽  
Subduction Fluids ◽  
Arc Setting

&lt;p&gt;Oceanic subduction and its last underthrusted part can both triggers arc-like magmatism. As the existence of multi-subduction zones in the Central Asian Orogenic Belt, controversy still surrounds on when and especially how the subduction of the (Paleo-Asian Ocean) PAO terminated. We present geochronological, geochemical, and Lu-Hf isotopic data for a suite of basalt-andesites, dacite-rhyolites and later trachyandesite-mugearitic dykes from the Khan-Bogd area in the Gobi Tianshan Zone (GTZ) of the southern Mongolia. U-Pb dating of zircons indicate the basalt-andesites and dacite-rhyolites were formed at ~334-338 Ma, and the dykes at ~300 Ma. These Early Carboniferous volcanic rocks display high U/Th, Ba/Th, low La/Sm and variable Zr/Nb ratios, implying the involvement of subduction fluids or sediment melt. They display arc geochemical features such as calc-alkaline and metaluminous nature and positive Ba and U and negative Nb, Ta and Ti anomalies. Moreover, their continental geochemical signals (e.g. positive Pb, K anomalies) and some old captured zircons implying a continental arc setting. Comparatively, the ~300 Ma dykes are characterized by high alkaline contents, which are common for coeval (~320-290 Ma) and widespread post-subductional granites there. Given a mainly crust-derived magma source for those granites, these dykes likely reflect a mantle disturbance due to: (1) their relative low SiO&lt;sub&gt;2 &lt;/sub&gt;(51.71-55.85 wt. %) and high Mg# (40.3-67.3) values, and (2) positive zircon &amp;#400;&lt;sub&gt;Hf&lt;/sub&gt;(t) (most &gt; 12). Considering a slab rollback model during the Carboniferous and Triassic, the mantle disturbance was possibly induced by the oceanic slab breakoff. Combined with previous work, this ~320-290 Ma slab breakoff-induced extension marks the closure of a wide secondary ocean (North Tianshan-Hegenshan ocean) north of the main ocean basin of the PAO. This research was financially supported by NSFC Projects (41730213, 42072264, 41902229, 41972237) and Hong Kong RGC GRF (17307918).&lt;/p&gt;

Earthquake ruptures tied to long-lived plate interface deformation 

2021 ◽  
Author(s):  
Nadaya Cubas ◽  
Philippe Agard ◽  
Roxane Tissandier
Keyword(s):  
Subduction Zones ◽  
Earthquake Hazard ◽  
Mechanical Analysis ◽  
Physical Parameters ◽  
Plate Interface ◽  
Interface Deformation ◽  
Earthquake Hazard Assessment ◽  
Interseismic Coupling ◽  
Rate And State Friction

&lt;p&gt;Predicting the spatial extent of mega-earthquakes is an essential ingredient of earthquake hazard assessment. In subduction zones, this prediction mostly relies on geodetic observations of interseismic coupling. However, such models face spatial resolution issues and are of little help to predict full or partial ruptures of highly locked patches. Coupling models are interpreted in the framework of the rate-and-state friction laws. However, these models are too idealized to take into account the effects of a geometrically or rheologically complex plate interface. In this study, we show, from the critical taper theory and a mechanical analysis of the topography, that all recent mega-earthquakes of the Chilean subduction zone are surrounded by distributed interplate deformation emanating from either underplating or basal erosion. This long-lived plate interface deformation builds up stresses ultimately leading to earthquake nucleation. Earthquakes then propagate along a relatively smooth surface and are stopped by segments of heterogeneously distributed deformation. Our results are consistent with long-term features of the subduction margin, with observed short-term deformation as well as physical parameters of recovered subducted fragments. They also provide an explanation for the apparent mechanical segmentation of the megathrust, reconciling many seemingly contradictory observations on the short- and long-term deformation. Consequently, we propose that earthquake segmentation relates to the distribution of deformation along the plate interface and that slip deficit patterns reflect the along-dip and along-strike distribution of the plate interface deformation. Topography would therefore mirror plate interface deformation and could serve to improve earthquake rupture prediction.&lt;/p&gt;

scholarly journals Ophiolitic Pyroxenites Record Boninite Percolation in Subduction Zone Mantle

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 565 ◽  
Author(s):  
Véronique Le Roux ◽  
Yan Liang
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Mantle Wedge ◽  
Major Element ◽  
Early Stage ◽  
Diffusion Modeling ◽  
Melt Infiltration ◽  
Melt Percolation ◽  
Back Arc ◽  
Parental Melts

The peridotite section of supra-subduction zone ophiolites is often crosscut by pyroxenite veins, reflecting the variety of melts that percolate through the mantle wedge, react, and eventually crystallize in the shallow lithospheric mantle. Understanding the nature of parental melts and the timing of formation of these pyroxenites provides unique constraints on melt infiltration processes that may occur in active subduction zones. This study deciphers the processes of orthopyroxenite and clinopyroxenite formation in the Josephine ophiolite (USA), using new trace and major element analyses of pyroxenite minerals, closure temperatures, elemental profiles, diffusion modeling, and equilibrium melt calculations. We show that multiple melt percolation events are required to explain the variable chemistry of peridotite-hosted pyroxenite veins, consistent with previous observations in the xenolith record. We argue that the Josephine ophiolite evolved in conditions intermediate between back-arc and sub-arc. Clinopyroxenites formed at an early stage of ophiolite formation from percolation of high-Ca boninites. Several million years later, and shortly before exhumation, orthopyroxenites formed through remelting of the Josephine harzburgites through percolation of ultra-depleted low-Ca boninites. Thus, we support the hypothesis that multiple types of boninites can be created at different stages of arc formation and that ophiolitic pyroxenites uniquely record the timing of boninite percolation in subduction zone mantle.

Fluid influence on the trace element compositions of subduction zone magmas

1991 ◽  
Vol 335 (1638) ◽  
pp. 377-392 ◽  
Keyword(s):  
Subduction Zones ◽  
Mantle Wedge ◽  
Chemical Fractionation ◽  
Ocean Island Basalts ◽  
Hydrous Melting ◽  
Dehydration Processes ◽  
Slab Dehydration ◽  
Subduction Magmatism ◽  
Element Flux ◽  
Continental Growth

Subduction zones represent major sites of chemical fractionation within the Earth. Element pairs which behave coherently during normal mantle melting may become strongly decoupled from one another during the slab dehydration processes and during hydrous melting conditions in the slab and in the mantle wedge. This results in the large ion lithophile elements (e.g. K, Rb, Th, U, Ba) and the light rare earth elements being transferred from the slab to the mantle wedge, and being concentrated within the mantle wedge by hydrous fluids, stabilized in hydrous phases such as hornblende and phlogopite, from where they are eventually extracted as magmas and contribute to growth of the continental crust. High-field strength elements (e.g. Nb, Ta, Ti, P, Zr) are insoluble in hydrous fluids and relatively insoluble in hydrous melts, and remain in the subducted slab and the adjacent parts of the mantle which are dragged down and contribute to the source for ocean island basalts. The required element fractionations result from interaction between specific mineral phases (hornblende, phlogopite, rutile, sphene, etc.) and hydrous fluids. In present day subduction magmatism the mantle wedge contributes dominantly to the chemical budget, and there is a requirement for significant convection to maintain the element flux. In the Precambrian, melting of subducted ocean crust may have been easier, providing an enhanced slab contribution to continental growth.

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