Three-dimensional thermal structure of subduction zones: effects of obliquity and curvature

Bengtson, A. K.; Keken, Peter E. van

doi:10.5194/sed-4-919-2012

Cited by 13 publications

(13 citation statements)

References 56 publications

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“…6). These results agree well with previous numerical modeling work (Bengtson and Van Keken, 2012;Morishige and van Keken, 2014;Ji and Yoshioka, 2015;Wada et al, 2015). Our systematic study of the influence of the 10 shape of the trench on the geotherm shows that a larger amplitude in the model (convex of concave) leads to a larger trench parallel flow and consequently a larger difference in the temperature at the plate interface.…”

Section: Implications Of Obliquity In Subduction Systemssupporting

confidence: 81%

“…Following our experiments, Φ remains certainly the first order parameter but we demonstrate that the trench parallel mantle flow influences on the temperature at the plate interface and may thus explain along-strike temperature differences in subduction zones. A 2D approach remains viable in systems with small obliquity, as stated in Bengtson and Van Keken (2012), but important variations of geometry should be considered in further studies to reliably represent subduction zone dynamics both for present-day and past systems. …”

Section: Implications Of Obliquity In Subduction Systemsmentioning

confidence: 99%

“…Kneller and van Keken, 2007). Numerical models also suggested that the obliquity of subduction zones may have an effect on the temperature at the subduction interface (Bengtson and Van Keken, 2012;Morishige and van Keken, 2014;Ji and Yoshioka, 25 2015) but did not explore the relationship of such effects with the geological record. These studies have primarily shown that mantle flow may be related to the geometry of the slab edges that lead to the development of toroidal cells (i.e.…”

Section: Introductionmentioning

confidence: 99%

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

Plunder¹,

Thieulot²,

Hinsbergen³

2018

Preprint

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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 5 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 trenchparallel 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 10 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.

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Section: Implications Of Obliquity In Subduction Systemssupporting

confidence: 81%

Section: Implications Of Obliquity In Subduction Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Plunder¹,

Thieulot²,

Hinsbergen³

2018

Preprint

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“…Geodynamical modeling studies of trench‐parallel flow have invoked along‐strike pressure gradients due to effects such as trench migration [e.g., Conder and Wiens , ], rapid flow around a slab edge facilitated by a non‐Newtonian rheology [e.g., Jadamec and Billen , , ], or complex slab morphology [ Kneller and van Keken , , ]. Oblique subduction may also play a role in transporting material in an along‐strike direction in mantle wedges [e.g., Nakajima et al ., ; Bengtson and van Keken , ] and may result in transpressive deformation in the shallow part of the mantle wedge [e.g., Mehl et al ., ].…”

Section: Conceptual Models For Subduction Zone Anisotropy and Mantle mentioning

confidence: 99%

Constraints on Subduction Geodynamics From Seismic Anisotropy

Long

2013

Reviews of Geophysics

187

234

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[1] Much progress has been made over the past several decades in delineating the structure of subducting slabs, but several key aspects of their dynamics remain poorly constrained. Major unsolved problems in subduction geodynamics include those related to mantle wedge viscosity and rheology, slab hydration and dehydration, mechanical coupling between slabs and the ambient mantle, the geometry of mantle flow above and beneath slabs, and the interactions between slabs and deep discontinuities such as the core-mantle boundary. Observations of seismic anisotropy can provide relatively direct constraints on mantle dynamics because of the link between deformation and the resulting anisotropy: when mantle rocks are deformed, a preferred orientation of individual mineral crystals or materials such as partial melt often develops, resulting in the directional dependence of seismic wave speeds. Measurements of seismic anisotropy thus represent a powerful tool for probing mantle dynamics in subduction systems. Here I review the observational constraints on seismic anisotropy in subduction zones and discuss how seismic data can place constraints on wedge, slab, and sub-slab anisotropy. I also discuss constraints from mineral physics investigations and geodynamical modeling studies and how they inform our interpretation of observations. I evaluate different models in light of constraints from seismology, geodynamics, and mineral physics. Finally, I discuss some of the major unsolved problems related to the dynamics of subduction systems and how ongoing and future work on the characterization and interpretation of seismic anisotropy can lead to progress, particularly in frontier areas such as understanding slab dynamics in the deep mantle.

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“…The speed of the slab is the projection of the plate velocity onto the cross section, leading to an effective reduction in plate convergence speed. As is shown in Bengtson and van Keken (2012) this approach of taking cross sections perpendicular to the trench and using the projected velocity component is preferred over the approach where the cross section is taken parallel to convergence velocity. As in Wada and Wang (2009) and Syracuse et al (2010) we assume in general full coupling between slab and wedge at depths below 80 km.…”

Section: Modeling Approachmentioning

confidence: 99%

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

2012

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Abstract. The cause of intermediate-depth (> 40 km) seismicity in subduction zones is not well understood. The viability of proposed mechanisms, which include dehydration embrittlement, shear instabilities and the presence of fluids in general, depends significantly on local conditions, including pressure, temperature and composition. The wellinstrumented and well-studied subduction zone below Northern Japan (Tohoku and Hokkaido) provides an excellent testing ground to study the conditions under which intermediatedepth seismicity occurs. This study combines new finite element models that predict the dynamics and thermal structure of the Japan subduction system with a high-precision hypocenter data base. The upper plane of seismicity is principally contained in the crustal portion of the subducting slab and appears to thin and deepen within the crust at depths > 80 km. The disappearance of seismicity overlaps in most of the region with the predicted phase change of blueschist to hydrous eclogite, which forms a major dehydration front in the crust. The correlation between the thermally predicted blueschist-out boundary and the disappearance of seismicity breaks down in the transition from the northern Japan to Kurile arc below western Hokkaido. Adjusted models that take into account the seismically imaged modified upper mantle structure in this region fail to adequately recover the correlation that is seen below Tohoku and eastern Hokkaido. We conclude that the thermal structure below Western Hokkaido is significantly affected by timedependent, 3-D dynamics of the slab. This study generally supports the role of fluids in the generation of intermediatedepth seismicity.

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Three-dimensional thermal structure of subduction zones: effects of obliquity and curvature

Cited by 13 publications

References 56 publications

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

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

Constraints on Subduction Geodynamics From Seismic Anisotropy

Thermal structure and intermediate-depth seismicity in the Tohoku-Hokkaido subduction zones

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