Physical properties of the Earth's core

Stacey F.D. (1972) Physical properties of the Earth's core. Geophysical Surveys, 1 1: 99-119. doi:10.1007/BF01449553


Author Stacey F.D.
Title Physical properties of the Earth's core
Journal name Geophysical Surveys
ISSN 0046-5763
Publication date 1972
Sub-type Article (original research)
DOI 10.1007/BF01449553
Volume 1
Issue 1
Start page 99
End page 119
Total pages 21
Publisher Kluwer Academic Publishers
Subject 1908 Geophysics
1906 Geochemistry and Petrology
Abstract Calculations of the compression and temperature gradient of the core are facilitated by the use of the thermodynamic Grüneisen ratio, γ=3αKs/ρ{variant}CP. A pressure-dependent factor in γ is found to have the same numerical value for the core as for laboratory iron, justifying the use of a constant value for γ (1.6) in core calculations. The density of the outer core is satisfied by the assumption that it contains about 15% of light elements, particularly sulphur, whereas the inner core is probably ironnickel with very little lighter component. The presence of sulphur in the outer core reduces its liquidus at least 600° below pure iron, so that the adiabatic gradient does not intersect the liquidus, as Higgins and Kennedy have shown would occur in a pure iron core. The inner core is probably close to its melting point, 4700 K, and the adiabatic temperature gradient of the outer is calculated with this as a fixed point, giving 3380 K at the core-mantle boundary. The estimated electrical resistivity of the outer core, 3×10-6 Σm, corresponds to a thermal conductivity of 28 W·m-1·deg-1, which, with the adiabatic core gradient gives a minimum of 3.9×1012 W of heat conduction to the mantle. The only plausible source of this much heat is the radioactive decay of potassium in the core. As pointed out by Goles, Lewis, and Hall and Murthy, the presence of potassium becomes geochemically probable once sulphur is admitted as a core constituent. Thus it appears that the recognition of sulphur in the core resolves the two major difficulties which we have faced in attempting to understand the core.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import
 
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Created: Tue, 12 Jul 2016, 02:38:33 EST by System User