scholarly journals Water Concentration in Single‐Crystal (Al,Fe)‐Bearing Bridgmanite Grown From the Hydrous Melt: Implications for Dehydration Melting at the Topmost Lower Mantle

2019 ◽  
Vol 46 (17-18) ◽  
pp. 10346-10357 ◽  
Author(s):  
Suyu Fu ◽  
Jing Yang ◽  
Shun‐ichiro Karato ◽  
Alexander Vasiliev ◽  
Mikhail Yu. Presniakov ◽  
...  
Keyword(s):  
Single Crystal ◽  
Lower Mantle ◽  
Water Concentration ◽  
Dehydration Melting ◽  
Hydrous Melt

Dehydration melting at the top of the lower mantle

Science ◽  
2014 ◽  
Vol 344 (6189) ◽  
pp. 1265-1268 ◽  
Author(s):  
B. Schmandt ◽  
S. D. Jacobsen ◽  
T. W. Becker ◽  
Z. Liu ◽  
K. G. Dueker
Keyword(s):  
Lower Mantle ◽  
Dehydration Melting

Reactive bulk assimilation: A model for crust-mantle mixing in silicic magmas

Geology ◽  
2005 ◽  
Vol 33 (8) ◽  
pp. 681-684 ◽  
Author(s):  
James S. Beard ◽  
Paul C. Ragland ◽  
Maria Luisa Crawford
Keyword(s):  
Dehydration Melting ◽  
Crustal Rocks ◽  
Host Magma ◽  
Ti Oxides ◽  
Energy Penalty ◽  
Magma Crystallization ◽  
Hydrous Melt ◽  
Silicic Magmas ◽  
Solid Form ◽  
Hydrous Magma

Abstract Bulk assimilation of small (millimeters to ∼1 km) fragments of crust—driven and (ultimately) masked by reactions during xenolith melting and magma crystallization—is an important mechanism for crust-mantle mixing. Xenoliths containing mica or amphibole undergo dehydration melting when incorporated into a host magma, yielding mainly plagioclase, pyroxene, Fe-Ti oxides, and hydrous melt. The xenolith is physically compromised by partial melting and begins to disintegrate; xenolithic melt and crystals are mixed into the host magma. Xenocrystic zircon is liberated at this stage. The cryptic character of assimilation is greatly enhanced in any hydrous magma by hydration crystallization reactions (the reverse of dehydration melting). All pyroxenes and oxides (phenocrysts, xenocrysts, or crystals having a hybrid signature) will be subject to these reactions, producing feldspars, amphiboles, and micas that incorporate material from several sources, a particularly effective mixing mechanism. Implicit in the model is a reduced energy penalty for bulk assimilation—much of the assimilant remains in solid form—compared to melt-assimilation models. A large role for bulk assimilation supports stoping as a credible mechanism for the ascent of magmas. While the assimilation of low-density crust and concomitant fractionation provide the isostatic impetus for ascent, the wholesale incorporation and processing of crustal rocks in the magma chamber helps create the room for ascent.

Single-crystal synchrotron X-ray diffraction study of wüstite and magnesiowüstite at lower-mantle pressures

2005 ◽  
Vol 12 (5) ◽  
pp. 577-583 ◽  
Author(s):  
Steven D. Jacobsen ◽  
Jung-Fu Lin ◽  
Ross J. Angel ◽  
Guoyin Shen ◽  
Vitali B. Prakapenka ◽  
...  
Keyword(s):  
Single Crystal ◽  
Diffraction Study ◽  
Lower Mantle ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Single‐crystal elasticity of MgSiO 3 bridgmanite to mid‐lower mantle pressure

2021 ◽  
Author(s):  
G. Criniti ◽  
A. Kurnosov ◽  
T. Boffa Ballaran ◽  
D. J. Frost
Keyword(s):  
Single Crystal ◽  
Lower Mantle

Single-crystal equation of state of phase D to lower mantle pressures and the effect of hydration on the buoyancy of deep subducted slabs

2013 ◽  
Vol 118 (12) ◽  
pp. 6124-6133 ◽  
Author(s):  
A. D. Rosa ◽  
M. Mezouar ◽  
G. Garbarino ◽  
P. Bouvier ◽  
S. Ghosh ◽  
...  
Keyword(s):  
Equation Of State ◽  
Single Crystal ◽  
Lower Mantle

scholarly journals Incorporation mechanism of Fe and Al into bridgmanite in a subducting mid-ocean ridge basalt and its crystal chemistry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Akihiko Nakatsuka ◽  
Hiroshi Fukui ◽  
Seiji Kamada ◽  
Naohisa Hirao ◽  
Makio Ohkawa ◽  
...  
Keyword(s):  
Single Crystal ◽  
Bond Length ◽  
Lower Mantle ◽  
Structural Distortion ◽  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
Coupled Substitution ◽  
The Difference ◽  
A Site ◽  
Ocean Ridge

AbstractThe compositional difference between subducting slabs and their surrounding lower-mantle can yield the difference in incorporation mechanism of Fe and Al into bridgmanite between both regions, which should cause heterogeneity in physical properties and rheology of the lower mantle. However, the precise cation-distribution has not been examined in bridgmanites with Fe- and Al-contents expected in a mid-ocean ridge basalt component of subducting slabs. Here we report on Mg0.662Fe0.338Si0.662Al0.338O3 bridgmanite single-crystal characterized by a combination of single-crystal X-ray diffraction, synchrotron 57Fe-Mössbauer spectroscopy and electron probe microanalysis. We find that the charge-coupled substitution AMg2+  + BSi4+  ↔ AFe3+(high-spin) + BAl3+ is predominant in the incorporation of Fe and Al into the practically eightfold-coordinated A-site and the sixfold-coordinated B-site in bridgmanite structure. The incorporation of both cations via this substitution enhances the structural distortion due to the tilting of BO6 octahedra, yielding the unusual expansion of mean <A–O> bond-length due to flexibility of A–O bonds for the structural distortion, in contrast to mean <B–O> bond-length depending reasonably on the ionic radius effect. Moreover, we imply the phase-transition behavior and the elasticity of bridgmanite in slabs subducting into deeper parts of the lower mantle, in terms of the relative compressibility of AO12 (practically AO8) and BO6 polyhedra.

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