scholarly journals Melting Phase Relations of KLB-1 Peridotite and Mid-Ocean Ridge Basalt and Gravitational Stabilities of Partical Silicate Melts at the Uppermost Lower Mantle

2019 ◽  
Vol 29 (2) ◽  
pp. 75-85
Author(s):  
Hideharu KUWAHARA ◽  
Ryuichi NOMURA ◽  
Ryoichi NAKADA ◽  
Tetsuo IRIFUNE
Keyword(s):  
Lower Mantle ◽  
Phase Relations ◽  
Silicate Melts ◽  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

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.

Widespread strombolian eruptions of mid-ocean ridge basalt

2009 ◽  
Vol 180 (2-4) ◽  
pp. 171-188 ◽  
Author(s):  
David A. Clague ◽  
Jennifer B. Paduan ◽  
Alice S. Davis
Keyword(s):  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
Strombolian Eruptions ◽  
Ocean Ridge

Evidence from rare gases for magma-chamber degassing of highly evolved mid-ocean-ridge basalt

Nature ◽  
1990 ◽  
Vol 343 (6257) ◽  
pp. 450-452 ◽  
Author(s):  
David E. Fisher ◽  
Michael R. Perfit
Keyword(s):  
Magma Chamber ◽  
Rare Gases ◽  
Ridge Basalt ◽  
Mid Ocean Ridge ◽  
Ocean Ridge ◽  
Highly Evolved
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