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Static compression of ε‐FeSi and an evaluation of reduced silicon as a deep Earth constituent
Author(s) -
Knittle Elise,
Williams Quentin
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl03346
Subject(s) - silicon , inner core , materials science , bulk modulus , outer core , mantle (geology) , earth (classical element) , elasticity (physics) , core (optical fiber) , mineralogy , composite material , metallurgy , geology , geophysics , mathematical physics , physics
The volume of ε‐FeSi has been measured to pressures of 50 GPa. No high pressure transformations are observed in this system, including after laser‐heating at high pressures. The bulk modulus of this phase is 209 (±6) GPa, with a pressure derivative of 3.5 (±0.4). This high bulk modulus will slightly elevate the thermochemically‐inferred pressure conditions at which chemical reactions between iron and mantle silicates should commence at mid‐mantle depths. Moreover, because of the relatively low pressure derivatives of the bulk moduli of FeSi alloys manifested both in our data and in previous shock results, silicon as the sole light alloying component of the outer core is unlikely to produce a sufficiently large change in the bulk sound speed of the outer core relative to pure iron liquid. Therefore, silicon is not likely to be the primary alloying component in the outer core, unless its effect on the elasticity of the outer core is fortuitously offset by other light alloying constituents: its role is probably that of a subsidiary constituent. Thus, silicon is unique (to date) among proposed major outer core alloying constituents in being potentially precludable on purely geophysical grounds.