The pyrite-type FeO2 H-Fe O2 system has been experimentally confirmed to be stable in Earth's lowermost mantle but there is limited information about its physical properties at high pressures constraining our unde...The pyrite-type FeO2 H-Fe O2 system has been experimentally confirmed to be stable in Earth's lowermost mantle but there is limited information about its physical properties at high pressures constraining our understanding of its potential geophysical implications for the deep Earth.Here,static calculations demonstrate that the pyrite-type FeO2 H-FeO2 system has a high density and Poisson's ratio and ultra-low seismic velocities at conditions of Earth's lowermost mantle.It provides a plausible mechanism for the origin of ultra-low velocity zones at Earth's D″layer.The incorporation of hydrogen in the pyrite-type FeO2H-FeO2 system tends to decrease the S wave velocity(VS)but increase the bulk sound velocity(VΦ),and can potentially explain the observed anti-correlation of VS and VΦin the lowermost mantle.Additionally,FeO2 H exhibits nearly isotropic whereas Fe O2 is highly anisotropic,which may help understand some seismic anisotropies at the core-mantle boundary.展开更多
基金financial support from the National Natural Science Foundation of China (Nos. 41473056 and 41472037)
文摘The pyrite-type FeO2 H-Fe O2 system has been experimentally confirmed to be stable in Earth's lowermost mantle but there is limited information about its physical properties at high pressures constraining our understanding of its potential geophysical implications for the deep Earth.Here,static calculations demonstrate that the pyrite-type FeO2 H-FeO2 system has a high density and Poisson's ratio and ultra-low seismic velocities at conditions of Earth's lowermost mantle.It provides a plausible mechanism for the origin of ultra-low velocity zones at Earth's D″layer.The incorporation of hydrogen in the pyrite-type FeO2H-FeO2 system tends to decrease the S wave velocity(VS)but increase the bulk sound velocity(VΦ),and can potentially explain the observed anti-correlation of VS and VΦin the lowermost mantle.Additionally,FeO2 H exhibits nearly isotropic whereas Fe O2 is highly anisotropic,which may help understand some seismic anisotropies at the core-mantle boundary.
