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- Dubrovinsky, L., et al.
(författare)
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Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle
- 2003
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 422:6927, s. 58-61
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Tidskriftsartikel (refereegranskat)abstract
- The boundary between the Earth's metallic core and its silicate mantle is characterized by strong lateral heterogeneity and sharp changes in density, seismic wave velocities, electrical conductivity and chemical composition(1-7). To investigate the composition and properties of the lowermost mantle, an understanding of the chemical reactions that take place between liquid iron and the complex Mg-Fe-Si-Al-oxides of the Earth's lower mantle is first required(8-15). Here we present a study of the interaction between iron and silica (SiO2) in electrically and laser-heated diamond anvil cells. In a multianvil apparatus at pressures up to 140 GPa and temperatures over 3,800 K we simulate conditions down to the core-mantle boundary. At high temperature and pressures below 40 GPa, iron and silica react to form iron oxide and an iron-silicon alloy, with up to 5 wt% silicon. At pressures of 85-140 GPa, however, iron and SiO2 do not react and iron-silicon alloys dissociate into almost pure iron and a CsCl-structured (B2) FeSi compound. Our experiments suggest that a metallic silicon-rich B2 phase, produced at the core-mantle boundary (owing to reactions between iron and silicate(2,9,10,13)), could accumulate at the boundary between the mantle and core and explain the anomalously high electrical conductivity of this region(6).
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