C. McCammon: Intermediate spin Fe 2+ in lower mantle perovskite Intermediate spin Fe Intermediate spin Fe 2+ 2+ in lower mantle in lower mantle perovskite perovskite C. McCammon, I. Kantor, O. Narygina, J. Rouquette, L. Dubrovinsky Bayerisches Geoinstitut, Universität Bayreuth, Germany U. Ponkratz, I. Sergueev, M. Mezouar ESRF, Grenoble, France V. Prakapenka APS, Chicago, USA Second VLab Workshop University of Minnesota August 5-10, 2007
21
Embed
C. McCammon: Intermediate spin Fe 2+ in lower mantle perovskite Intermediate spin Fe 2+ in lower mantle perovskite C. McCammon, I. Kantor, O. Narygina,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
Intermediate spin FeIntermediate spin Fe2+2+ in lower mantle perovskite in lower mantle perovskite
C. McCammon, I. Kantor, O. Narygina, J. Rouquette, L. DubrovinskyBayerisches Geoinstitut, Universität Bayreuth, Germany
U. Ponkratz, I. Sergueev, M. MezouarESRF, Grenoble, France
V. PrakapenkaAPS, Chicago, USA
Second VLab WorkshopUniversity of Minnesota
August 5-10, 2007
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
Evidence for FeEvidence for Fe2+2+ spin transition: XES spin transition: XESBadro et al. (2004)Mg0.9Fe0.1SiO3 perovskite
decrease of intensitymeans
reduction of S
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
Evidence for FeEvidence for Fe2+2+ spin transition: NFS spin transition: NFS
Li et al. (2004)
Mg0.9Fe0.1SiO3 perovskite
Fe2+ high spin
Fe3+ high spin
McCammon (1998) increase in QS with P
Jackson et al. (2005)
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
Spectra at high P,TSpectra at high P,T
55 GPa 800 K
Mössbauer spectroscopy
Fe2+ intermediate spin
62 GPa 1000 K
Nuclear forward scattering
Fe2+ intermediate spin
→ Intermediate spin stable at higher T
Fe0.12Mg0.88SiO3
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
Effect of AlEffect of Al3+3+ and Fe and Fe3+3+ on spin transition on spin transitionMg0.86Fe0.14Si0.98Al0.02O3
• 5 sample loadings
• 42 Mössbauer spectra
• P = 0 to 70 GPa
• T = 300 to 700 K
→ Fe2+ spin transition
also occurs in the
presence of trivalent
cations
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
Spin number variation with P,TSpin number variation with P,T
Sturhahn et al. 2005
Fe0.12Mg0.88SiO3
C. McCammon: Intermediate spin Fe2+ in lower mantle perovskite
SummarySummary
• Fe2+ in (Mg,Fe)(Si,Al)O3 perovskite is predominantly intermediate spin throughout entire lower mantle
• this conclusion is consistent with all existing data
• spin transition in Fe3+ not required to explain data, but cannot be ruled out
• spin transition might be coupled to lattice distortion. Variations in sample environment (e.g., deviatoric stress) can change spin state stability (already calculated by Li et al. 2005)
• challenge to computational community to reproduce experimental results on spin state
• return spotlight to perovskite phase to assess implications of spin state change for mantle properties and dynamics