title: Effect of iron oxidation state on the electrical conductivity of the Earth's lower mantle.
abstract: Iron can adopt different spin states in the lower mantle. Previous studies indicate that the dominant lower-mantle phase, magnesium silicate perovskite (which contains at least half of its iron as Fe(3+)), undergoes a Fe(3+) high-spin to low-spin transition that has been suggested to cause seismic velocity anomalies and a drop in laboratory-measured electrical conductivity. Here we apply a new synchrotron-based method of Mössbauer spectroscopy and show that Fe(3+) remains in the high-spin state in lower-mantle perovskite at conditions throughout the lower mantle. Electrical conductivity measurements show no conductivity drop in samples with high Fe(3+), suggesting that the conductivity drop observed previously on samples with high Fe(2+) is due to a transition of Fe(2+) to the intermediate-spin state. Correlation of transport and elastic properties of lower-mantle perovskite with electromagnetic and seismic data may provide a new probe of heterogeneity in the lower mantle.
authors: European Synchrotron Radiation Facility, BP 220, Grenoble F-38043, France.
authors: V
authors: V
authors: Potapkin
authors: C
authors: C
authors: McCammon
authors: K
authors: K
authors: Glazyrin
authors: A
authors: A
authors: Kantor
authors: I
authors: I
authors: Kupenko
authors: C
authors: C
authors: Prescher
authors: R
authors: R
authors: Sinmyo
authors: G V
authors: GV
authors: Smirnov
authors: A I
authors: AI
authors: Chumakov
authors: R
authors: R
authors: Rüffer
authors: L
authors: L
authors: Dubrovinsky
references: J Synchrotron Radiat. 2009 Nov;16(Pt 6):737-41
references: 19844007
references: J Synchrotron Radiat. 2012 Jul;19(Pt 4):559-69
references: 22713890
references: Science. 2004 Jul 16;305(5682):383-6
references: 15256667
references: Proc Jpn Acad Ser B Phys Biol Sci. 2007 May;83(3):97-100
references: 24019587
references: Nature. 2004 Mar 25;428(6981):409-12
references: 15042086
references: Science. 2008 Apr 4;320(5872):89-91
references: 18388291
references: Rev Sci Instrum. 2012 Dec;83(12):125102
references: 23278021
references: Phys Rev Lett. 2011 Mar 18;106(11):118501
references: 21469904
references: Science. 2005 May 6;308(5723):807-8
references: 15879203