scholarly journals The Mantle Transition Zone in Fennoscandia: Enigmatic High Topography Without Deep Mantle Thermal Anomaly

2019 ◽  
Vol 46 (7) ◽  
pp. 3652-3662
Author(s):  
Anna Makushkina ◽  
Benoît Tauzin ◽  
Hrvoje Tkalčić ◽  
Hans Thybo
Keyword(s):  
Transition Zone ◽  
Thermal Anomaly ◽  
Mantle Transition Zone ◽  
Deep Mantle ◽  
High Topography

Subducting slab morphology and mantle transition zone upwelling in double-slab subduction models with inward-dipping directions

2019 ◽  
Vol 218 (3) ◽  
pp. 2089-2105 ◽  
Author(s):  
Tianyang Lyu ◽  
Zhiyuan Zhu ◽  
Benjun Wu
Keyword(s):  
Transition Zone ◽  
Lower Mantle ◽  
Numerical Models ◽  
Local Maximum ◽  
Substantial Effect ◽  
Mantle Flow ◽  
Slab Geometry ◽  
Mantle Transition Zone ◽  
Mantle Viscosity ◽  
Deep Mantle

SUMMARY Lithospheric plates on the Earth's surface interact with each other, producing distinctive structures comprising two descending slabs. Double-slab subduction with inward-dipping directions represents an important multiplate system that is not yet well understood. This paper presents 2-D numerical models that investigate the dynamic process of double-slab subduction with inward dipping, focussing on slab geometry and mantle transition zone upwelling flow. This unique double-slab configuration limits trench motion and causes steep downward slab movement, thus forming fold piles in the lower mantle and driving upward mantle flow between the slabs. The model results show the effects of lithospheric plate properties and lower-mantle viscosity on subducting plate kinematics, overriding plate stress and upward mantle flow beneath the overriding plate. Appropriate lower-mantle strength (such as an upper–lower mantle viscosity increase with a factor of 200) allows slabs to penetrate into the lower mantle with periodical buckling. While varying the length and thickness of a long overriding plate (≥2500) does not have a substantial effect on slab geometry, its viscosity has a marked impact on slab evolution and mantle flow pattern. When the overriding plate is strong, slabs exhibit an overturned geometry and hesitate to fold. Mantle transition zone upwelling velocity depends on the speed of descending slabs. The downward velocity of slabs with a large negative buoyancy (caused by thickness or density) is very fast, inducing a significant transition zone upwelling flow. A stiff slab slowly descends into the deep mantle, causing a small upward flow in the transition zone. In addition, the temporal variation of mantle upwelling velocity shows strong correlation with the evolution of slab folding geometry. In the double subduction system with inward-dipping directions, the mantle transition zone upwelling exhibits oscillatory rise with time. During the backward-folding stage, upwelling velocity reaches its local maximum. Our results provide new insights into the deep mantle source of intraplate volcanism in a three-plate interaction system such as the Southeast Asia region.

scholarly journals Anomalously deep mantle transition zone below Central Europe: Evidence of lithospheric instability

2009 ◽  
Vol 36 (21) ◽  
Author(s):  
György Hetényi ◽  
Graham W. Stuart ◽  
Gregory A. Houseman ◽  
Frank Horváth ◽  
Endre Hegedűs ◽  
...  
Keyword(s):  
Transition Zone ◽  
Central Europe ◽  
Mantle Transition Zone ◽  
Deep Mantle

Theoretical modeling of the regular olivine intergrowths in the mimetic paramorphosis after ringwoodite and wadsleyite

2018 ◽  
pp. 3-12
Author(s):  
B. B. Shkursky
Keyword(s):  
Transition Zone ◽  
Theoretical Modeling ◽  
Mantle Transition Zone ◽  
Misorientation Angles

Theoretical modeling of regular olivine grains misorientations in mimetic paramorphoses after ringwoodite and wadsleyite, the formation of which during the ascension of matter from the Mantle Transition Zone is expected, has been carried out. The coordinates of the misorientation axes and the misorientation angles, characterizing 10 operations of alignment in the pair intergrowths of olivine grains, eight of which are twins, are calculated. Possible conditions for the formation of mimetic paramorphoses predicted here, and the chances of their persistence are discussed. The calculated orientations are compared with the known twinning laws of olivine.

scholarly journals A thin mantle transition zone beneath the equatorial Mid-Atlantic Ridge

Nature ◽  
2021 ◽  
Vol 589 (7843) ◽  
pp. 562-566
Author(s):  
Matthew R. Agius ◽  
Catherine A. Rychert ◽  
Nicholas Harmon ◽  
Saikiran Tharimena ◽  
J.-Michael Kendall
Keyword(s):  
Transition Zone ◽  
Mantle Transition Zone ◽  
Mid Atlantic Ridge
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