The composition and physical properties of the Earth's mantle and core
The chemical and physical properties of the Earth's deep interior, particularly the mantle and core, have controlled both the dynamics and the evolution of the planet. Seismic studies are only capable of determining the velocity of seismic waves and, in an average sense, densities at depth. The physical interpretation of seismic results relies on understanding the properties of materials. The experiments allow comparisons to be made between high pressure experiments and corresponding seismological observations, providing insight into the Earth's large-scale chemical structure. Electrical resistivity measurements to pressures of 83 GPa and temperatures ranging from 300 K to 4300 K confirm the presence of both crystalline and liquid metallic phases of FeO at pressures above 60 to 70 GPa and temperatures above 1000 K. By experimentally determining the melting temperature of FeO to 100 GPa, and of a model core composition at 83 GPa, it was found that the solid-melt equilibria can be described by complete solid solution across the Fe-FeO system at pressures above 70 GPa. The data suggest that the temperature at the Earth's core-mantle boundary is close to 4800 (+ or - 500) K. The thermal expansion of silicate perovskite, the most abundant in the Earth's lower mantle, was measured between 300 and 840 K at zero pressure. These data are combined with the 300 K isotherm of silicate perovskite, measured to pressures of 112 GPa, to obtain a thermal equation of state for this mineral. The thermal equation of state allows comparisons to be made between the physical properties of silicate perovskite and mineral assemblages dominated by perovskite with the same properties for lower mantle as determined by seismology. Chemical reactions between silicate perovskite and liquid iron were documented at pressures greater than 70 G
- Research Organization:
- California Univ., Berkeley, CA (USA)
- OSTI ID:
- 6864485
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ALLOYS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
EARTH PLANET
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
EQUATIONS
EQUATIONS OF STATE
EXPANSION
HIGH PRESSURE
IRON
IRON ALLOYS
ISOTHERMS
MELTING
METALS
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITES
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PLANETS
SEISMIC WAVES
SEISMOLOGY
SILICA
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
THERMAL EXPANSION
TRANSITION ELEMENTS