Iron-rich silicates in the Earth's D'' layer.
High-pressure experiments and theoretical calculations demonstrate that an iron-rich ferromagnesian silicate phase can be synthesized at the pressure-temperature conditions near the core-mantle boundary. The iron-rich phase is up to 20% denser than any known silicate at the core-mantle boundary. The high mean atomic number of the silicate greatly reduces the seismic velocity and provides an explanation to the low-velocity and ultra-low-velocity zones. Formation of this previously undescribed phase from reaction between the silicate mantle and the iron core may be responsible for the unusual geophysical and geochemical signatures observed at the base of the lower mantle.
Mao
Wendy L
WL
Department of the Geophysical Sciences and Chicago Center for Cosmochemistry, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA. wmao@uchicago.edu
Meng
Yue
Y
Shen
Guoyin
G
Prakapenka
Vitali B
VB
Campbell
Andrew J
AJ
Heinz
Dion L
DL
Shu
Jinfu
J
Caracas
Razvan
R
Cohen
Ronald E
RE
Fei
Yingwei
Y
Hemley
Russell J
RJ
Mao
Ho-kwang
HK