Silicon in the metal phase of enstatite chondrites and some geochemical implications

Details Silicon in the metal phase of enstatite chondrites and some geochemical implications Silicon in the metal phase of enstatite chondrites and some geochemical implications

Aug 1961

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1961gecoa..25....1r&link_type=abstract

Geochimica et Cosmochimica Acta, vol. 25, Issue 1, pp.1-13

Computer Science

16

Scientific paper

Some recent hypotheses have proposed that silicon occurs as a major component of the earth's core. Since the chemical evolution of the earth may have been analogous in some respects to that which occurred in meteorites, a search for silicon was made in the metal phases of chondrites. Using X-ray and chemical methods, it was established that between 2 and 6 atomic per cent of silicon occurred in solid solution in the metal phases of all eight enstatite chondrites which were examined. No silicon was found in the metal phase of ordinary chondrites. Evidence relating to the possible occurrence of silicon in the earth's core is reviewed, and the significance of the new meteoritic data in relation to this hypothesis is discussed in some detail. A study of the conditions which accompany the segregation of a core, both in the earth and in the parent meteoritic body, lead to the conclusion that the core is unlikely to be in chemical equilibrium with the surrounding mantle. One of the principal effects of this disequilibrium is the diffusion of silicon from the core into the adjacent region of the mantle, resulting in the reduction of oxidized iron and precipitation of metallic iron. This effect may be responsible for the anomalous seismic velocity gradients which are observed in the bottom 200 km of the mantle. This region is likely to be mechanically unstable, owing to the tendency of precipitated iron to collect and sink into the core. Owing to inhomogenieties in ionic and electronic transport properties in this region, attainment of chemical equilibrium across the core-mantle boundary is accompanied by generation of electric currents. These may be relevant to the origin of the earth's magnetic field, and may also affect the electromagnetic coupling between core and mantle.

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