Interaction of a mantle plume and a moving plate: insights from numerical modeling

2020 ◽  
Author(s):  
Sascha Brune ◽  
Marzieh Baes ◽  
Taras Gerya ◽  
Stephan Sobolev
Keyword(s):  
Boundary Condition ◽  
Mantle Plume ◽  
Critical Radius ◽  
Oceanic Lithosphere ◽  
Plate Motion ◽  
Moving Plate ◽  
Kinematic Boundary Condition ◽  
Mechanical Models ◽  
Stationary Plate ◽  
Do So

<p>The impingement of a hot buoyant mantle plume onto the lithosphere can result in either breaking of the lithosphere, which might results in subduction initiation or in under-plating of the plume beneath the lithosphere. Key natural examples of the former and latter are formation of subduction along the southern margin of Caribbean and northwestern South America in the late Cretaceous as well as the hotspot chains of Hawaii, respectively. In previous studies the interaction of a buoyant mantle plume with lithosphere was investigated either for the case of stationary lithosphere or for moving lithosphere but ignoring the effect of magmatic weakening of the lithosphere above the plume head. In this study we aim to investigate the response of a moving lithosphere to the arrival of a stationary mantle plume including the effect of magmatic lithospheric weakening. To do so we use 3d thermo-mechanical models employing the finite difference code I3ELVIS. Our setup consists of an oceanic lithosphere, mantle plume and asthenosphere till depth of 400 km. The moving plate is simulated by imposing a kinematic boundary condition on the lithospheric part of the side boundaries. The mantle plume in our models has a mushroom shape. The experiments differ in the age of the lithosphere, rate of the plate motion and size of the mantle plume. For different combinations of these parameters model results show either (1) breaking of the lithosphere and initiation of subduction above the plume head or (2) asymmetric spreading of the plume material below the lithosphere without large deformation of the lithosphere. We find that the critical radius of the plume that breaks the lithosphere and initiates subduction depends on plume buoyancy and the lithospheric age, but not on the plate speed. In general, the modeling results for the moving plate are similar to the results for a stationary plate, but the shapes of the region of the deformed lithosphere differ.</p>

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

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

<p>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.</p>

scholarly journals Motion fluency effects on object preference is limited to learned context

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0244110
Author(s):  
Jonathan Charles Flavell ◽  
Bryony McKean
Keyword(s):  
Boundary Condition ◽  
Original Work ◽  
Object Motion ◽  
Preference Change ◽  
Behavioural Interventions ◽  
Stimulus Choice ◽  
Critical Boundary ◽  
The Moment ◽  
Do So ◽  
Object Preference

Recently, Flavell et al. (2019) demonstrated that an object’s motion fluency (how smoothly and predictably it moves) influences liking of the object itself. Though the authors demonstrated learning of object-motion associations, participants only preferred fluently associated objects over disfluently associated objects when ratings followed a moving presentation but not a stationary presentation. In the presented experiment, we tested the possibility that this apparent failure of associative learning / evaluative conditioning was due to stimulus choice. To do so we replicate part of the original work but change the ‘naturally stationary’ household object stimuli with winged insects which move in a similar way to the original motions. Though these more ecologically valid stimuli should have facilitated object to motion associations, we again found that preference effects were only apparent following moving presentations. These results confirm the potential of motion fluency for ‘in the moment’ preference change, and they demonstrate a critical boundary condition that should be considered when attempting to generalise fluency effects across contexts such as in advertising or behavioural interventions.

scholarly journals IODP Expedition 330: Drilling the Louisville Seamount Trail in the SW Pacific

2013 ◽  
Vol 15 ◽  
pp. 11-22 ◽  
Author(s):  
A. A. P. Koppers ◽  
T. Yamazaki ◽  
J. Geldmacher ◽  
Keyword(s):  
Mantle Plume ◽  
Mantle Source ◽  
Isotope Geochemistry ◽  
Oceanic Lithosphere ◽  
Similar Amount ◽  
Mantle Plumes ◽  
Large Variability ◽  
Sw Pacific ◽  
Integrated Ocean Drilling Program ◽  
The Pacific

Deep-Earth convection can be understood by studying hotspot volcanoes that form where mantle plumes rise up and intersect the lithosphere, the Earth's rigid outer layer. Hotspots characteristically leave age-progressive trails of volcanoes and seamounts on top of oceanic lithosphere, which in turn allow us to decipher the motion of these plates relative to "fixed" deep-mantle plumes, and their (isotope) geochemistry provides insights into the long-term evolution of mantle source regions. However, it is strongly suggested that the Hawaiian mantle plume moved ~15° south between 80 and 50 million years ago. This raises a fundamental question about other hotspot systems in the Pacific, whether or not their mantle plumes experienced a similar amount and direction of motion. Integrated Ocean Drilling Program (IODP) Expedition 330 to the Louisville Seamounts showed that the Louisville hotspot in the South Pacific behaved in a different manner, as its mantle plume remained more or less fixed around 48°S latitude during that same time period. Our findings demonstrate that the Pacific hotspots move independently and that their trajectories may be controlled by differences in subduction zone geometry. Additionally, shipboard geochemistry data shows that, in contrast to Hawaiian volcanoes, the construction of the Louisville Seamounts doesn’t involve a shield-building phase dominated by tholeiitic lavas, and trace elements confirm the rather homogenous nature of the Louisville mantle source. Both observations set Louisville apart from the Hawaiian-Emperor seamount trail, whereby the latter has been erupting abundant tholeiites (characteristically up to 95% in volume) and which exhibit a large variability in (isotope) geochemistry and their mantle source components. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.15.02.2013" target="_blank">10.2204/iodp.sd.15.02.2013</a>

Radial Anisotropy and it's Relation to Fast and Slow Moving Tectonic Plates

2021 ◽  
Author(s):  
Tak Ho ◽  
Keith Priestley ◽  
Eric Debayle
Keyword(s):  
Upper Mantle ◽  
Large Scale ◽  
Oceanic Lithosphere ◽  
Azimuthal Anisotropy ◽  
Plate Motion ◽  
Moho Depth ◽  
Dispersion Characteristics ◽  
Anisotropic Models ◽  
Ocean Ridges ◽  
Average Dispersion

&lt;p&gt;We present a new radially anisotropic (&lt;strong&gt;&amp;#958;)&lt;/strong&gt;&amp;#160;tomographic model for the upper mantle to transition zone depths derived from a large Rayleigh (~4.5 x 10&lt;sup&gt;6&amp;#160;&lt;/sup&gt;paths) and Love (~0.7 x 10&lt;sup&gt;6&lt;/sup&gt;&amp;#160;paths) wave path average dispersion curves with periods of 50-250 s and up to the fifth overtone. We first extract the path average dispersion characteristics from the waveforms. Dispersion characteristics for common paths (~0.3 x 10&lt;sup&gt;6&lt;/sup&gt;&amp;#160;paths) are taken from the Love and Rayleigh datasets and jointly inverted for isotropic V&lt;sub&gt;s&amp;#160;&lt;/sub&gt;and&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;. CRUST1.0 is used for crustal corrections and a model similar to PREM is used as a starting model. V&lt;sub&gt;s&lt;/sub&gt;&amp;#160;and&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;&amp;#160;are regionalised for a 3D model. The effects of azimuthal anisotropy are accounted for during the regionalisation. Our model confirms large-scale upper mantle features seen in previously published models, but a number of these features are better resolved because of the increased data density of the fundamental and higher modes coverage from which our&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;(z) was derived. Synthetic tests show structures with radii of 400 km can be distinguished easily. Crustal perturbations of +/-10% to V&lt;sub&gt;p&lt;/sub&gt;, V&lt;sub&gt;s&lt;/sub&gt;&amp;#160;and density, or perturbations to Moho depth of +/-10 km over regions of 400 km do not significantly change the model. The global average decreases from&amp;#160;&lt;strong&gt;&amp;#958;~&lt;/strong&gt;1.06 below the Moho to&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;~1 at ~275 km depth. At shallow depths beneath the oceans&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;&gt;1 as is seen in previously published global mantle radially anisotropic models. The thickness of this layer increases slightly with the increasing age of the oceanic lithosphere. At ~200 km and deeper depths below the fast-spreading East Pacific Rise and starting at somewhat greater depths beneath the slower spreading ridges,&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;&lt;1. At depths &amp;#8805;200 km and deeper depths below most of the backarc basins of the western Pacific&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;&lt;1. The signature of mid-ocean ridges vanishes at about 150 km depth in V&lt;sub&gt;s&lt;/sub&gt;&amp;#160;while it extends much deeper in the&amp;#160;&lt;strong&gt;&amp;#958;&lt;/strong&gt;&amp;#160;model suggesting that upwelling beneath mid-ocean ridges could be more deeply rooted than previously believed. The pattern of radially anisotropy we observe, when compared with the pattern of azimuthal anisotropy determined from Rayleigh waves, suggests that the shearing at the bottom of the plates is only sufficiently strong to cause large-scale preferential alignment of the crystals when the plate motion exceeds some critical value which Debayle and Ricard (2013) suggest is about 4 cm/yr.&lt;/p&gt;

Mixed Convection in Air in an Open Ended Cavity With a Moving Plate Parallel to the Cavity Open Surface

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Nicola Bianco ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Mixed Convection ◽  
Plate Motion ◽  
Uniform Heat Flux ◽  
Geometrical Parameters ◽  
Heated Plate ◽  
Open Surface ◽  
Moving Plate ◽  
Plate Temperature

In this study, a numerical investigation of mixed convection in air in an open ended cavity, with a moving plate parallel to the cavity open surface, is carried out. The moving plate has a constant velocity, whereas a vertical plate of the open cavity is heated at uniform heat flux. All the other walls are adiabatic. The numerical analysis is obtained by means of the commercial code FLUENT. Two configurations, assisting and opposing, are analyzed. In the assisting configuration, natural convection is supported by the plate motion, whereas, in the opposing configuration, natural convection and plate motion have opposing effects. The effect of different geometrical parameters, heat flux and moving plate velocity are analyzed. Results in terms of heated plate and moving plate temperature profiles are presented and simple monomial correlation equations for both the configurations are proposed between the terms Nu/Re0.6 and Ri.

scholarly journals Layered Lithospheric Mantle Beneath the Ontong Java Plateau: Implications from Xenoliths in Alnöite, Malaita, Solomon Islands

2004 ◽  
Vol 45 (10) ◽  
pp. 2011-2044 ◽  
Author(s):  
AKIRA ISHIKAWA ◽  
SHIGENORI MARUYAMA ◽  
TSUYOSHI KOMIYA
Keyword(s):  
Mantle Plume ◽  
Solomon Islands ◽  
Oceanic Lithosphere ◽  
Mantle Xenoliths ◽  
Garnet Lherzolite ◽  
Ontong Java Plateau ◽  
Basaltic Melt ◽  
Normative Quartz ◽  
Intermediate Part ◽  
Compositional Diversity

Abstract A varied suite of mantle xenoliths from Malaita, Solomon Islands, was investigated to constrain the evolution of the mantle beneath the Ontong Java Plateau. Comprehensive petrological and thermobarometric studies make it possible to identify the dominant processes that produced the compositional diversity and to reconstruct the lithospheric stratigraphy in the context of a paleogeotherm. P–T estimates show that both peridotites and pyroxenites can be assigned to a shallower or deeper origin, separated by a garnet-poor zone of 10 km between 90 and 100 km. This zone is dominated by refractory spinel harzburgites (Fo91–92), indicating the occurrence of an intra-lithospheric depleted zone. Shallower mantle (∼Moho to 95 km) is composed of variably metasomatized peridotite with subordinate pyroxenite derived from metacumulates. Deeper mantle (∼95–120 km) is represented by pyroxenite and variably depleted peridotites that are unevenly distributed; the least-depleted garnet lherzolite (Fo90–91) lies just below the garnet-poor depleted zone (∼100–110 km), whereas the presence of pyroxenite is restricted to the deepest region (∼110–120 km), together with relatively Fe-enriched garnet lherzolite (Fo87–88). This depth-related variation (including the depleted zone) can be explained by assuming that the degree of melting for a basalt–peridotite hybrid source was systematically different at each level of arrival depth within a single adiabatically ascending mantle plume: (1) the depleted zone at the top of the mantle plume, where garnet was totally consumed in the residual solid; (2) an intermediate part of the plume dominated by the least-depleted garnet lherzolite just above the depth of the peridotite solidus; (3) the deepest pyroxenite-rich zone, whose petrochemical variation is best explained by the interaction between peridotite and normative quartz-rich basaltic melt, below the solidus of peridotite and liquidus of basalt. We explain the obvious lack of pyroxenites at shallower depths as the effective extraction of hybrid melt from completely molten basalt through the partially molten ambient peridotite, which caused the voluminous eruption of the Ontong Java Plateau basalts. From these interpretations, we conclude that the lithosphere forms a genetically unrelated two-layered structure, comprising shallower oceanic lithosphere and deeper impinged plume material, which involved a recycled basaltic component, now present as a pyroxenitic heterogeneity. This interpretation for the present lithospheric structure may explain the seismically anomalous root beneath the Ontong Java Plateau.

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