Seismological evidence of mantle flow driving plate motions at a palaeo-spreading centre

2014 ◽  
Vol 7 (5) ◽  
pp. 371-375 ◽  
Author(s):  
Shuichi Kodaira ◽  
Gou Fujie ◽  
Mikiya Yamashita ◽  
Takeshi Sato ◽  
Tsutomu Takahashi ◽  
...  
Keyword(s):  
Mantle Flow ◽  
Plate Motions

scholarly journals Feedbacks between a non-Newtonian upper mantle, mantle viscosity structure and mantle dynamics

2020 ◽  
Vol 224 (2) ◽  
pp. 961-972
Author(s):  
A G Semple ◽  
A Lenardic
Keyword(s):  
Upper Mantle ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Mantle Flow ◽  
Mantle Dynamics ◽  
Plate Motions ◽  
Low Viscosity ◽  
Mantle Viscosity ◽  
Flow Feature ◽  
Mantle Rheology

SUMMARY Previous studies have shown that a low viscosity upper mantle can impact the wavelength of mantle flow and the balance of plate driving to resisting forces. Those studies assumed that mantle viscosity is independent of mantle flow. We explore the potential that mantle flow is not only influenced by viscosity but can also feedback and alter mantle viscosity structure owing to a non-Newtonian upper-mantle rheology. Our results indicate that the average viscosity of the upper mantle, and viscosity variations within it, are affected by the depth to which a non-Newtonian rheology holds. Changes in the wavelength of mantle flow, that occur when upper-mantle viscosity drops below a critical value, alter flow velocities which, in turn, alter mantle viscosity. Those changes also affect flow profiles in the mantle and the degree to which mantle flow drives the motion of a plate analogue above it. Enhanced upper-mantle flow, due to an increasing degree of non-Newtonian behaviour, decreases the ratio of upper- to lower-mantle viscosity. Whole layer mantle convection is maintained but upper- and lower-mantle flow take on different dynamic forms: fast and concentrated upper-mantle flow; slow and diffuse lower-mantle flow. Collectively, mantle viscosity, mantle flow wavelengths, upper- to lower-mantle velocities and the degree to which the mantle can drive plate motions become connected to one another through coupled feedback loops. Under this view of mantle dynamics, depth-variable mantle viscosity is an emergent flow feature that both affects and is affected by the configuration of mantle and plate flow.

An analytical model concerning the possible initiation of subduction between the India and Africa plates, caused by the Morondova plume

2020 ◽  
Author(s):  
Bernhard Steinberger ◽  
Douwe van Hinsbergen
Keyword(s):  
Subduction Zones ◽  
Plate Tectonics ◽  
Eastern Mediterranean ◽  
Plate Boundary ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Motions ◽  
Subduction Initiation ◽  
Euler Pole ◽  
Geodynamic Processes

<p>Identifying the geodynamic processes that trigger the formation of new subduction zones is key to understand what keeps the plate tectonic cycle going, and how plate tectonics once started. Here we discuss the possibility of plume-induced subduction initiation. Previously, our numerical modeling revealed that mantle upwelling and radial push induced by plume rise may trigger plate motion change, and plate divergence as much as 15-20 My prior to LIP eruption. Here we show that, depending on the geometry of plates, the distribution of cratonic keels and where the plume rises, it may also cause a plate rotation around a pole that is located close to the same plate boundary where the plume head impinges: If that occurs near one end of the plate boundary, an Euler pole of the rotation may form along that plate boundary, with extension on one side, and convergence on the other.  This concept is applied to the India-Africa plate boundary and the Morondova plume, which erupted around 90 Ma, but may have influenced plate motions as early as 105-110 Ma. If there is negligible friction, i.e. there is a pre-existing weak plate boundary, we estimate that the total amount of convergence generated in the northern part of the India-Africa plate boundary can exceed 100 km, which is widely thought to be sufficient to initiate forced, self-sustaining subduction. This may especially occur if the India continental craton acts like an “anchor” causing a comparatively southern location of the rotation pole of the India plate. Geology and paleomagnetism-based reconstructions of subduction initiation below ophiolites from Pakistan, through Oman, to the eastern Mediterranean reveal that E-W convergence around 105 Ma caused forced subduction initiation, and we tentatively postulate that this is triggered by Morondova plume head rise. Whether the timing of this convergence is appropriate to match observations on subduction initiation as early as 105 Ma depends on the timing of plume head arrival, which may predate eruption of the earliest volcanics. It also depends on whether a plume head already can exert substantial torque on the plate while it is still rising – for example, if the plate is coupled to the induced mantle flow by a thick craton.</p>

Reconciling surface plate motions with rapid three-dimensional mantle flow around a slab edge

Nature ◽  
2010 ◽  
Vol 465 (7296) ◽  
pp. 338-341 ◽  
Author(s):  
Margarete A. Jadamec ◽  
Magali I. Billen
Keyword(s):  
Three Dimensional ◽  
Mantle Flow ◽  
Plate Motions ◽  
Surface Plate

Subduction zone seismo-dynamics: how to bridge the gap between long-term subduction dynamics and megathrust seismicity?

2021 ◽  
Author(s):  
Adam Beall ◽  
Fabio A. Capitanio ◽  
Ake Fagereng ◽  
Ylona van Dinther
Keyword(s):  
Stress State ◽  
Subduction Zone ◽  
Subduction Zones ◽  
Large Scale ◽  
Large Earthquake ◽  
Force Balance ◽  
Mantle Flow ◽  
Plate Interface ◽  
Plate Motions

<p>The largest and most devastating earthquakes on Earth occur along subduction zones. Here, long-term plate motions are accommodated in cycles of strain accumulation and release. Episodic strain release occurs by mechanisms ranging from rapid earthquakes to slow-slip and quasi-static creep along the plate interface. Slip styles can vary between and within subduction zones, though it is unclear what controls margin-scale variability. Current approaches to seismo-tectonics primarily relate the stress state and seismogenesis at subduction margins to interface material properties and plate kinematics, constrained by recorded seismic slip, GPS motions and integrated strain. At larger spatio-temporal scales, significant progress has been made towards the understanding of subduction dynamics and emerging self-consistent plate motions, tectonics and stress coupling at plate margins. The margin stress state is ultimately linked to the force balance arising from interactions between the slab, mantle flow and upper plate. These mantle and lithosphere dynamics are thus expected to govern the tectonic regimes under which seismicity occurs. It remains unclear how these longer- and shorter-term perspectives can be reconciled. We review the aspects of large-scale subduction dynamics that control tectonic loading at plate margins, discuss possible influences on the stress state of the plate interface, and summarise recent advances in integrating the earthquake cycle and large-scale dynamics. It is plausible that variations in large-scale subduction dynamics could systematically influence seismicity, though it remains unclear to what degree this interplay occurs directly through the plate interface stress state and/or indirectly, corresponding to variation of other subduction zone characteristics. While further constraints of the geodynamic controls on the nature of the plate interface and their incorporation into probabilistic earthquake models is required, their ongoing development holds promise for an improved understanding of the global variation of large earthquake occurrence and their associated risk.</p>

scholarly journals Mantle flow and plate motions

1986 ◽  
Vol 87 (1) ◽  
pp. 155-171 ◽  
Author(s):  
J. F. Harper
Keyword(s):  
Mantle Flow ◽  
Plate Motions

scholarly journals The influence of plate motions on three-dimensional back arc mantle flow and shear wave splitting

2000 ◽  
Vol 105 (B12) ◽  
pp. 28009-28033 ◽  
Author(s):  
Chad E. Hall ◽  
Karen M. Fischer ◽  
E. M. Parmentier ◽  
Donna K. Blackman
Keyword(s):  
Shear Wave ◽  
Three Dimensional ◽  
Shear Wave Splitting ◽  
Mantle Flow ◽  
Plate Motions ◽  
Wave Splitting ◽  
Back Arc

scholarly journals Effects of basal drag on subduction dynamics from 2D numerical models

2020 ◽  
Author(s):  
Lior Suchoy ◽  
Saskia Goes ◽  
Benjamin Maunder ◽  
Fanny Garel ◽  
Rhodri Davies
Keyword(s):  
Numerical Models ◽  
Force Balance ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Motions ◽  
Flow Models ◽  
Plate Size ◽  
Modelling Studies ◽  
Subduction System

Abstract. Subducting slabs are an important driver of plate motions, yet the force balance governing subduction dynamics remains incompletely understood. Basal drag has been proposed to be a minor contributor to subduction forcing, because of the lack of correlation between plate size and velocity in observed and reconstructed plate motions. Furthermore, in single subduction system models, low basal drag, associated with a low ratio of asthenospheric to lithospheric viscosity, leads to subduction behaviour most consistent with the observation that trench migration velocities are generally low compared to convergence velocities. By contrast, analytical calculations and global mantle flow models indicate basal drag can be substantial. In this study, we revisit this problem by examining the drag at the base of the lithosphere, for a single subduction system, in 2D models with a free trench and composite non-linear rheology. We compare the behaviour of short and long plates for a range of asthenospheric and lithospheric rheologies. We reproduce results from previous modelling studies, including low ratios of trench over plate motions. However, we also find that any combination of asthenosphere and lithosphere viscosity that produces Earth-like subduction behaviour leads to a correlation of velocities with plate size, due to the role of basal drag. By examining Cenozoic plate motion reconstructions, we find that slab age and plate size are positively correlated: higher slab pull for older plates tends to be offset by higher basal drag below these larger plates. This, in part, explains the lack of plate velocity-size correlation in observations, despite the important role of basal drag in the subduction force-balance.

Coupled evolution of supercontinents and lower mantle structure

2021 ◽  
Author(s):  
Xianzhi Cao ◽  
Nicolas Flament ◽  
Ömer Bodur ◽  
Dietmar Müller
Keyword(s):  
Lower Mantle ◽  
Reference Frames ◽  
Plate Motion ◽  
Motion Path ◽  
Mantle Flow ◽  
Plate Tectonic ◽  
Mantle Structure ◽  
Plate Motions ◽  
Flow Models ◽  
Over Time

<p>The relationships between plate motions and basal mantle structure remain poorly understood, with some models implying that the basal mantle structure has remained stable over time, while others suggest that it could be shaped by the aggregation and dispersal of supercontinents. Here we investigate the plate-basal mantle relationship through 1) building a series of end-member plate tectonic models over one billion years, and 2) creating mantle flow models assimilated by those plate models. To achieve that, we build synthetic plate tectonic models dating from 1 Ga to 250 Ma that we connect to an existing palaeogeographical plate reconstruction from 250 Ma to create a relative plate motion model for the last 1 Gyr, in which supercontinent breakup and reassembly occur via introversion. We consider three distinct reference frames that result in different net lithospheric rotation. We find that the flow models predict a dominant degree-2 lower mantle structure most of the time and that they are in first-order agreement (~70% spatial match) with tomographic models. Model thermochemical structures at the base of the mantle may split into smaller structures when slabs sink onto them, and smaller basal structures may merge into larger ones as a result of slab pushing. The basal thermochemical structure under the superocean is large and continuous, whereas the basal thermochemical structure under the supercontinent is smaller and progressively assembles during and shortly after supercontinent assembly. In the models, plumes also develop preferentially along the edge of the basal thermochemical structures and tend to migrate towards the interior of basal structures over time as they interact with the slabs. Lone plumes can also form away from the main thermochemical structures, often within a small network of sinking slabs. Lone plumes may migrate between basal structures. We analyse the relationship between imposed tectonic velocities and deep mantle flow, and find that at spherical harmonic degree 2, the maxima of lower mantle radial flow and temperature follow the motion path of the maxima of surface divergence. It may take ~160-240 Myr for lower mantle structure to reflect plate motion changes when the lower mantle is reorganised by slabs sinking onto basal thermochemical structures, and/or when slabs stagnate in the transition zone before sinking to the lower mantle. Basal thermochemical structures move at less than 0.6 °/Myr in our models with a temporal average of 0.16 °/Myr when there is no net lithospheric rotation, and between 0.20-0.23 °/Myr when net lithospheric rotation exists and is induced to the lower mantle. Our results suggest that basal thermochemical structures are not stationary, but rather linked to global plate motions and plate boundary reconfigurations, reflecting the dynamic nature of the co-evolving plate-mantle system.</p>

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