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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 23, 2212, doi:10.1029/2003GL018515, 2003

High-pressure alloying of potassium and iron: Radioactivity in the Earth's core?

Kanani K. M. Lee

Department of Earth and Planetary Science, University of California, Berkeley, USA


Raymond Jeanloz

Department of Earth and Planetary Science, University of California, Berkeley, USA


Abstract

High-resolution x-ray diffraction provides evidence that potassium (K) alloys with iron (Fe) when the two pure elements are heated together at pressures above ∼26 gigapascals (GPa). Increases of 2–3% in volume of the ɛ (hexagonal close packed: hcp) high-pressure phase of Fe can be attributed to the incorporation of ∼1 atomic% (∼7000 ppm by weight) K into Fe. Our results provide experimental support for predictions, derived from quantum mechanical calculations, that pressure can induce the alloying of K with Fe due to a change in the chemical-bonding character of K from alkaline- to transition-metal. Radioactive decay through the incorporation of 40K into the core could therefore be an important source of energy deep inside the Earth, helping to power the geodynamo and mantle dynamics.

Received 28 August 2003; accepted 20 October 2003; published 10 December 2003.

Index Terms: 3924 Mineral Physics: High-pressure behavior; 8124 Tectonophysics: Earth's interior—composition and state; 8130 Tectonophysics: Heat generation and transport.

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Citation: Lee, K. K. M., and R. Jeanloz (2003), High-pressure alloying of potassium and iron: Radioactivity in the Earth's core?, Geophys. Res. Lett., 30(23), 2212, doi:10.1029/2003GL018515.