Model for the formation of the earth's core

Journal Article · Tue Feb 15 00:00:00 EST 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB088iS02p0A501· OSTI ID:5775218

McCammon, C A; Ringwood, A E; Jackson, I

The recent discovery of a phase transformation in Fe/sub 0.94/O by Jeanloz and Ahrens has allowed a more detailed development of a model for core formation involving oxygen as the principal light alloying element in the core. It is predicted, based on calculations, that an increasing pressure in the system FeO-MgO will result in a gradual exsolution of an almost pure high-pressure phase FeO(hpp), leaving an iron-depleted (Fe,Mg)O rocksalt (B1) phase. We also predict that FeO(hhp) will form a low-melting point alloy with Fe at high temperature and high pressure. On the basis of our interpretations, we have constructed a model for core segregation. Assuming the earth to have accreted from the primordial solar nebula as a relatively homogeneous mixture of metallic iron and silicate-oxide phases, core segregation involving oxygen would commence at a depth where pressure is sufficiently high to cause exsolution of FeO(hpp) from the rocksalt phase, and temperature is sufficiently high to allow formation of an Fe-FeO(hpp) melt. A gravitational instability arises, leading to vertical differentiation of the earth as molten blobs of the metal sink downwards to form the core and the residual depleted silicate material coalesces to form large bodies which rise diapirically upwards to form the mantle.

• Research Organization: Research School of Earth Sciences Australian National University, Canberra, A. C. T. 2600 Australia
• OSTI ID: 5775218
• Journal Information: J. Geophys. Res.; (United States), Vol. 88:S1
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
EARTH PLANET
GEOLOGIC MODELS
PLANETARY EVOLUTION
EARTH MANTLE
GRAVITATIONAL INSTABILITY
IRON OXIDES
MAGNESIUM OXIDES
PHASE TRANSFORMATIONS
PRESSURE DEPENDENCE
SILICATES
TEMPERATURE EFFECTS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
INSTABILITY
IRON COMPOUNDS
MAGNESIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANETS
PLASMA INSTABILITY
SILICON COMPOUNDS
SOLAR SYSTEM EVOLUTION
TRANSITION ELEMENT COMPOUNDS
580200* - Geophysics- (-1989)