Affiliation:
1. Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
2. CARS, University of Chicago, Chicago, IL 60637, USA.
Abstract
Unexplained features have been observed seismically near the middle (∼1700-kilometer depth) and bottom of the Earth's lower mantle, and these could have important implications for the dynamics and evolution of the planet. (Mg,Fe)SiO
3
perovskite is expected to be the dominant mineral in the deep mantle, but experimental results are discrepant regarding its stability and structure. Here we report in situ x-ray diffraction observations of (Mg,Fe)SiO
3
perovskite at conditions (50 to 106 gigapascals, 1600 to 2400 kelvin) close to a mantle geotherm from three different starting materials, (Mg
0.9
Fe
0.1
)SiO enstatite, MgSiO
3
glass, and an MgO+SiO
2
mixture. Our results confirm the stability of (Mg,Fe)SiO
3
perovskite to at least 2300-kilometer depth in the mantle. However, diffraction patterns above 83 gigapascals and 1700 kelvin (1900-kilometer depth) cannot presently rule out a possible transformation from
Pbnm
perovskite to one of three other possible perovskite structures with space group
P
2
1
/
m
,
Pmmn
, or
P
4
2
/
nmc
.
Publisher
American Association for the Advancement of Science (AAAS)
Cited by
89 articles.
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