Whole-mantle convection and the transition-zone water filter

Nature ◽  
2003 ◽  
Vol 425 (6953) ◽  
pp. 39-44 ◽  
Author(s):  
David Bercovici ◽  
Shun-ichiro Karato
Keyword(s):  
Transition Zone ◽  
Mantle Convection ◽  
Water Filter ◽  
Zone Water

The Transition-Zone Water Filter Model for Global Material Circulation: Where Do We Stand?

2013 ◽  
pp. 289-313 ◽  
Author(s):  
Shun-Ichiro Karato ◽  
David Bercovici ◽  
Garrett Leahy ◽  
Guillaume Richard ◽  
Zhicheng Jing
Keyword(s):  
Transition Zone ◽  
Filter Model ◽  
Water Filter ◽  
Material Circulation ◽  
Zone Water

Sharpness of the 410-km discontinuity from the P410s and P2p410s seismic phases

2019 ◽  
Author(s):  
Lev Vinnik ◽  
Yangfan Deng ◽  
Grigoriy Kosarev ◽  
Sergey Oreshin ◽  
Zhou Zhang ◽  
...  
Keyword(s):  
Transition Zone ◽  
Southern Africa ◽  
Amplitude Ratio ◽  
Southern China ◽  
Broad Band ◽  
Receiver Functions ◽  
P Wave ◽  
Seismic Model ◽  
Yangtze Craton ◽  
Zone Water

Summary Sharpness of the 410-km boundary is of interest because it is sensitive to water content in the transition zone. We evaluate the width of the 410-km discontinuity with a new seismic method. Our estimates are inferred from the amplitude ratio of the P2p410s and P410s seismic phases that are detected in P-wave receiver functions. We applied this method to seismic recordings from arrays of broad-band stations deployed in central Fennoscandia, southern Africa and southern China. The obtained estimates of width of the 410-km discontinuity range from 10 to 22 km and always exceed the width of 7 km which is expected for anhydrous conditions. The enlarged width may be interpreted in terms of hydrous conditions, but we have found only one region (the eastern Yangtze Craton in China) where the broad 410-km discontinuity, as expected, is accompanied by a broad transition zone. Water in the transition zone may be a kind of a global phenomenon, but evidence of the enlarged width of the transition zone may be missing in most of our data because the reference seismic model is affected by water, as well.

Mantle convection with continental drift and heat source around the mantle transition zone

2013 ◽  
Vol 24 (3-4) ◽  
pp. 1080-1090 ◽  
Author(s):  
Hiroki Ichikawa ◽  
Masanori Kameyama ◽  
Kenji Kawai
Keyword(s):  
Heat Source ◽  
Transition Zone ◽  
Mantle Convection ◽  
Continental Drift ◽  
Mantle Transition Zone

scholarly journals Neo-Tethys geodynamics and mantle convection: from extension to compression in Africa and a conceptual model for obduction

2016 ◽  
Vol 53 (11) ◽  
pp. 1190-1204 ◽  
Author(s):  
Laurent Jolivet ◽  
Claudio Faccenna ◽  
Philippe Agard ◽  
Dominique Frizon de Lamotte ◽  
Armel Menant ◽  
...  
Keyword(s):  
Transition Zone ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Large Scale ◽  
Time Window ◽  
Numerical Models ◽  
Conveyor Belt ◽  
Arabian Plate ◽  
African Plate ◽  
Northern Margin

Since the Mesozoic, Africa has been under extension with shorter periods of compression associated with obduction of ophiolites on its northern margin. Less frequent than “normal” subduction, obduction is a first order process that remains enigmatic. The closure of the Neo-Tethys Ocean, by the Upper Cretaceous, is characterized by a major obduction event, from the Mediterranean region to the Himalayas, best represented around the Arabian Plate, from Cyprus to Oman. These ophiolites were all emplaced in a short time window in the Late Cretaceous, from ∼100 to 75 Ma, on the northern margin of Africa, in a context of compression over large parts of Africa and Europe, across the convergence zone. The scale of this process requires an explanation at the scale of several thousands of kilometres along strike, thus probably involving a large part of the convecting mantle. We suggest that alternating extension and compression in Africa could be explained by switching convection regimes. The extensional situation would correspond to steady-state whole-mantle convection, Africa being carried northward by a large-scale conveyor belt, while compression and obduction would occur when the African slab penetrates the upper–lower mantle transition zone and the African plate accelerates due to increasing plume activity, until full penetration of the Tethys slab in the lower mantle across the 660 km transition zone during a 25 Myr long period. The long-term geological archives on which such scenarios are founded can provide independent time constraints for testing numerical models of mantle convection and slab–plume interactions.

A mechanism for ocean-floor spreading

1971 ◽  
Vol 268 (1192) ◽  
pp. 731-731 ◽  
Keyword(s):  
Transition Zone ◽  
Upper Mantle ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Garnet Peridotite ◽  
Ocean Floor ◽  
Ocean Floor Spreading ◽  
Melted Layer ◽  
Lithospheric Plates ◽  
Melted Material

I wish to suggest a mechanism for ocean-floor spreading, other than deep mantle convection cells. If the geotherm intersects the mantle solidus at the base of the upper mantle, a partly melted layer will result. It will be less dense than the overlying unmelted garnet peridotite lithosphere and the situation will be gravitationally unstable. It will be more voluminous than the overlying unmelted mantle and will distend the lithosphere which will break up into plates. It will have low rigidity and decouple those lithospheric plates from the underlying transition zone and lower mantle. Melted material, perhaps with crystals, will escape in two ways.

Global electromagnetic induction constraints on transition-zone water content variations

Nature ◽  
2009 ◽  
Vol 460 (7258) ◽  
pp. 1003-1006 ◽  
Author(s):  
Anna Kelbert ◽  
Adam Schultz ◽  
Gary Egbert
Keyword(s):  
Water Content ◽  
Transition Zone ◽  
Electromagnetic Induction ◽  
Zone Water
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