scholarly journals Garnet-controlled very low velocities in the lower mantle transition zone at sites of mantle upwelling

Terra Nova ◽  
2018 ◽  
Vol 30 (5) ◽  
pp. 333-340 ◽  
Author(s):  
Thorsten J. Nagel ◽  
Erik Duesterhoeft ◽  
Christian Schiffer
Keyword(s):  
Transition Zone ◽  
Lower Mantle ◽  
Mantle Upwelling ◽  
Mantle Transition Zone

scholarly journals Mantle Transition Zone Thickness Beneath the Middle East: Evidence for Segmented Tethyan Slabs, Delaminated Lithosphere, and Lower Mantle Upwelling

2018 ◽  
Vol 123 (6) ◽  
pp. 4886-4905 ◽  
Author(s):  
Ayoub Kaviani ◽  
Eric Sandvol ◽  
Ali Moradi ◽  
Georg Rümpker ◽  
Zheng Tang ◽  
...  
Keyword(s):  
Middle East ◽  
Transition Zone ◽  
Lower Mantle ◽  
Mantle Upwelling ◽  
Mantle Transition Zone

Stability of Al-bearing superhydrous phase B at the mantle transition zone and the uppermost lower mantle

2018 ◽  
Vol 103 (8) ◽  
pp. 1221-1227 ◽  
Author(s):  
Sho Kakizawa ◽  
Toru Inoue ◽  
Hideto Nakano ◽  
Minami Kuroda ◽  
Naoya Sakamoto ◽  
...  
Keyword(s):  
Transition Zone ◽  
Lower Mantle ◽  
Mantle Transition Zone

Mantle transition zone discontinuities beneath the Indochina Peninsula: Implications for slab subduction and mantle upwelling

2017 ◽  
Vol 44 (14) ◽  
pp. 7159-7167 ◽  
Author(s):  
Youqiang Yu ◽  
Stephen S. Gao ◽  
Kelly H. Liu ◽  
Ting Yang ◽  
Mei Xue ◽  
...  
Keyword(s):  
Transition Zone ◽  
Mantle Upwelling ◽  
Indochina Peninsula ◽  
Mantle Transition Zone

scholarly journals High-pressure phase of brucite stable at Earth’s mantle transition zone and lower mantle conditions

2016 ◽  
Vol 113 (49) ◽  
pp. 13971-13976 ◽  
Author(s):  
Andreas Hermann ◽  
Mainak Mookherjee
Keyword(s):  
High Pressure ◽  
Transition Zone ◽  
Lower Mantle ◽  
Direct Detection ◽  
Geophysical Methods ◽  
High Pressure Phase ◽  
Mantle Transition Zone ◽  
Earth’S Mantle ◽  
3D Network ◽  
Pressure Phase

We investigate the high-pressure phase diagram of the hydrous mineral brucite, Mg(OH)2, using structure search algorithms and ab initio simulations. We predict a high-pressure phase stable at pressure and temperature conditions found in cold subducting slabs in Earth’s mantle transition zone and lower mantle. This prediction implies that brucite can play a much more important role in water transport and storage in Earth’s interior than hitherto thought. The predicted high-pressure phase, stable in calculations between 20 and 35 GPa and up to 800 K, features MgO6 octahedral units arranged in the anatase–TiO2 structure. Our findings suggest that brucite will transform from a layered to a compact 3D network structure before eventual decomposition into periclase and ice. We show that the high-pressure phase has unique spectroscopic fingerprints that should allow for straightforward detection in experiments. The phase also has distinct elastic properties that might make its direct detection in the deep Earth possible with geophysical methods.

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.

Prominent thermal anomalies in the mantle transition zone beneath the Transantarctic Mountains

Geology ◽  
2020 ◽  
Vol 48 (7) ◽  
pp. 748-752
Author(s):  
Erica L. Emry ◽  
Andrew A. Nyblade ◽  
Alan Horton ◽  
Samantha E. Hansen ◽  
Jordi Julià ◽  
...  
Keyword(s):  
Transition Zone ◽  
Upper Mantle ◽  
Lower Mantle ◽  
Low Velocity ◽  
Mantle Transition Zone ◽  
Thermal Anomalies ◽  
Victoria Land ◽  
Convective Thermal ◽  
Mantle Processes ◽  
Transantarctic Mountains

Abstract The Transantarctic Mountains (TAMs), Antarctica, exhibit anomalous uplift and volcanism and have been associated with regions of thermally perturbed upper mantle that may or may not be connected to lower mantle processes. To determine if the anomalous upper mantle beneath the TAMs connects to the lower mantle, we interrogate the mantle transition zone (MTZ) structure under the TAMs and adjacent parts of East Antarctica using 12,500+ detections of P-to-S conversions from the 410 and 660 km discontinuities. Our results show distinct zones of thinner-than-global-average MTZ (∼205–225 km, ∼10%–18% thinner) beneath the central TAMs and southern Victoria Land, revealing throughgoing convective thermal anomalies (i.e., mantle plumes) that connect prominent upper and lower mantle low-velocity regions. This suggests that the thermally perturbed upper mantle beneath the TAMs and Ross Island may have a lower mantle origin, which could influence patterns of volcanism and TAMs uplift.

scholarly journals Evolution of diamond-forming systems of the mantle transition zone: ringwoodite peritectic reaction (Mg,Fe)2SiO4 (experiment AT 20 GPa)

2019 ◽  
Vol 64 (9) ◽  
pp. 986-994
Author(s):  
А. V. Spivak ◽  
Yu. А. Litvin ◽  
Е. S. Zakharchenko ◽  
D. А. Simonova ◽  
L. S. Dubrovinsky
Keyword(s):  
Experimental Study ◽  
Transition Zone ◽  
Lower Mantle ◽  
Peritectic Reaction ◽  
Mantle Transition Zone ◽  
Earth’S Mantle ◽  
Silicate Carbonate ◽  
Melting Relations ◽  
Carbonate Melt

The peritectic reaction of ringwoodite (Mg,Fe)2SiO4 and silicate-carbonate melt with formation of magnesiowustite (Fe,Mg)O, stishovite SiO2 and Mg, Na, Ca, K-carbonates is revealed by experimental study at 20 GPa of melting relations of the multicomponent MgO-FeO-SiO2-Na2CO3-CaCO3-K2CO3 system of the Earth’s mantle transition zone. A reaction of CaCO3 and SiO2 with the formation of Ca-perovskite CaSiO3 is also detected. It is shown that the peritectic reaction of ringwoodite and melt with the formation of stishovite physic-chemically controls the fractional ultrabasic-basic evolution of both magmatic and diamond-forming systems of the deep horizons of the transition zone up to its boundary with the Earth’s lower mantle.

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