Evolution of attached and detached slabs and their associated mantle dynamics

final report for NASA Grant NAG 5-1312
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National Aeronautics and Space Administration, National Technical Information Service, distributor , [Washington, DC, Springfield, Va
Slabs., Subduction z
Statementprincipal investigator: Albert T. Hsui.
Series[NASA contractor report] -- NASA CR-191920., NASA contractor report -- NASA CR-191920.
ContributionsUnited States. National Aeronautics and Space Administration.
The Physical Object
FormatMicroform
Pagination1 v.
ID Numbers
Open LibraryOL14693733M

Slab dip angles are found to be transient features. As they penetrate into the mantle and increase their lengths, the associated gravitational torque also increases resulting in a downward pulling of the slab to the steeper dip angle.

This is especially true once a slab penetrates the olivine-spinel phase boundary at about km : Albert T. Hsui. Get this from a library. Evolution of attached and detached slabs and their associated mantle dynamics: final report for NASA Grant NAG [Albert T Hsui; United States.

National Aeronautics and Space Administration.]. The mantle exerts another resistive force called anchor force F a to any forward or backward motion of the slab associated with trench advance or rollback (Fig. 1C; Scholtz and Campos, ).

The stratification in the viscosity between upper and lower mantle δη is critical in the slab dynamic evolution (e.g., Enns et al., ). ment of continental Evolution of attached and detached slabs and their associated mantle dynamics book by detached slabs in the mantle may play a role in the long term pro-cessesofcrustalrecycling[HildebrandandBowring, ].

[4] Given the potential implications of slab detachment, it is important to better understand the dynamics of slab detachment. In particular, we investigate the first-order thermomechanical pro-Cited by: transient slab ponding, from the mantle drag induced upon slab penetration into the lower mantle, and from an associated surge of mantle upwelling beneath Africa.

This process started at ~65–55Ma for Tibet-Himalaya, when the Tethyan slab penetrated into the lower mantle, and ~10 Myr later in the Andes, when the Nazca slab did. This surge of. et al. For example, viscous mantle flow associated with subduction of a cold, dense slab causes subsidence creating a dynamic topographic low(DTL;Figb).TheDTLcanextendthousands of kilometres from the subduction zone and have an amplitude of several hundred metres to more than 1 km depending on the dip and age of the slab (e.g.

Abstract Phase transformations in model mantle compositions and those in subducting slabs have been reviewed to a depth of km on the basis of recent high‐pressure experimental data. Seismic velocity and density profiles in these compositions have also been.

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Billen () studied the dynamics of slabs in mantle transition zone by coupling a similar thermomechanical model with a transformation kinetics model based on Mosenfelder et al.

The. Any detached lower mantle slab may, when viewed in isolation, be associated with a large number of geological records, since post-detachment plate motions may have displaced these records over thousands of kilometres relative to the location where its slab remnant sinks in the mantle.

subducted slab material can drive surface plate motions. If the slab is detached from the subducting plate, as in Figure 1a, the downward motion of the slab induces mantle flow that exerts tractions on the base of nearby plates, driving both subducting and overriding plates toward the subduction zone.

If the slab remains attached to the. The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate.

Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the.

Hot mantle from the two adjacent cells rises at the ridge axis, creating new ocean crust. The top limb of the convection cell moves horizontally away from the ridge crest, as does the new seafloor. The outer limbs of the convection cells plunge down into the deeper mantle, dragging oceanic crust as well.

This takes place at the deep sea trenches. the global‐scale magmatism, tectonics, mantle dynamics, and thermal evolution history for the Earth since the Early Paleozoic. Citation: Zhang, N., S. Zhong, W. Leng, and Z.‐X. Li (), A model for the evolution of the Earth’s mantle structure since.

Resolving the modes of mantle convection through Earth history, i.e. when plate tectonics started and what kind of mantle dynamics reigned before, is essential to the understanding of the evolution of the whole Earth system, because plate tectonics influences.

Cold, dense subducting lithosphere provides the primary force driving tectonic plates at Earth's surface. The force available to drive the plates depends on a balance between the buoyancy forces driving subduction and the mechanical and buoyancy forces resisting subduction.

Because both the buoyancy and rheology of the slab and mantle depend on temperature, composition, grain size, water. As the Pacific–Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates.

Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography.

The geodynamic model reproduces the first-order plate velocity evolution of the Australian plate, with a transient ∼5 m.y. period of acceleration from 2 to 8 cm/yr during upper mantle slab lengthening, an ∼5 m.y.

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period of rapid plate motion (∼5–8 cm/yr), and a short. Summary. We present 3-D laboratory experiments constructed to investigate the pattern of mantle flow around a subducting slab under different boundary conditio.

1] Comparisons of the paleogeographic record with seismic tomography sections from the mantle below Asia indicate that detached slab remnants associated with a range of ages since subduction. In summary, all the evidence we presented leads us to propose our scenario of the mantle dynamics, the crustal formation, and the hydrothermal activity of the Southern Mariana Trough back-arc basin: The subducting slab is located at the depth of – km just beneath the spreading axis that is different from most of the other areas in the.

The asthenosphere is the part of the mantle that flows and moves the plates of the Earth. The Mantle. The mantle is the layer located directly under the sima.

It is the largest layer of the Earth, miles thick. The mantle is composed of very hot, dense rock. This layer of.

Geophysics of Slab Dynamics: Jeju Session 2: Subduction Dynamics and Mantle Convection Paul Tackley Subduction in Global Models of Mantle Convection wit. Some slabs stagnate in the mantle transition zone (MTZ) for tens of millions of years, such as beneath Europe, East Asia, and North America.

Slab stagnation above the is explained by the combined effects of the endothermic phase transition and associated viscosity jump, particularly if the trench retreats and slabs roll back through the. nition of the importance of slab pull, and that subducting slabs are essentially cold downwellings, it is becomingmore widely accepted that the plates are an integral part of mantle convection, or more to the point they are mantle convec-tion [e.g., Davies and Richards, ].

However, the idea that the plates arise from or are generated by. dehydrating subducting slab into their mantle source region.

Description Evolution of attached and detached slabs and their associated mantle dynamics PDF

Subduction of a narrow oceanic basin is considered to be the most probable cause of the East Carpathian magmatism and its migration. As thick continental crust began to enter the northern part of the trench at around 9 Ma, slab breakoff began although subduction of the detached slab.

Slab breakoff, detachment of oceanic lithosphere highly expected during arc-continent collision, is one of the important mechanisms inducing passive upwelling of the asthenosphere and magma generation in arc environments [1].

In order to better understand the mantle dynamics of slab. Seismic tomography imaging shows that there are high-velocity anomalies landward of the Monterey, Guadalupe, and Magdalena microplates, which we interpret as the fossil slabs still attached to the remnant oceanic microplates.

The fossil Guadalupe slab extends to a depth of km or more, and the Monterey slab extends deeper than km. We build upon previous modeling studies and specifically test the Schmandt and Humphreys () dangling slab scenario by addressing further questions concerning the effects of slab chemical variations and nearby subduction dynamics on the residence time of stalled slabs within the upper mantle.

Although we do find that effects such as chemical. In a global geodynamic model, Conrad et al. [] concluded that slabs are likely to be detached from their subducting plate, which in turn reduce overall slab pull to produce a giant earthquake.

However, their models did not incorporate detailed geometry of subducting slabs and thus failed to match the present-day slab pull force arising from. Second, subducting slabs excite large-scale convecting cells that interact with multiple plate fragments.

Plate fragments connected to slabs drag the mantle, and conversely, fragments that are not attached to any slab are dragged by the interior flow, with fragments pulled by connected slabs moving faster.

Another possibility is that the northeastern end of the Eastern Alps slab in excess of km length (Figs. B2c, d) is an amalgamation of the Adriatic and European slabs, with the excess length representing a segment of torn, Oligocene to early Miocene European slab that, in the images of Dando et al.

(, their Figs. 10, 12), descends to the. Such upper mantle flow around the subducting slab was also suggested in the subduction rollback model (e.g. Funiciello et al., ; Piromallo and Faccenna, ). Similarly, in the western portion of the Eastern Alps, a deep EU slab can be associated with anisotropy due to stored deformation from past episodes of the tectonic evolution.1 1 2 Deflection of mantle flow beneath subducting slabs and the origin of sub-slab 3 anisotropy 4 5 6 Karen Paczkowski1,2*, Christopher J.

Thissen2, Maureen D. Long2, and Laurent G. J. Montési1 7 8 9 1Department of Geology, University of Maryland, College Park, MD USA 10 2Department of Geology and Geophysics, Yale University, New Haven, CT USA.