Hafnium-tungsten Isotopes

The refractory elements, hafnium (Hf) and tungsten (W), are marvels when it comes to studying the history of planetary bodies and the timing of accretion, differentiation, and core formation. The siderophile nature of W and the lithophile manner of Hf make the short-lived Hf-W isotope system a valuable dating technique in planetary science (for example, see PSRD article: Hafnium, Tungsten, and the Differentiation of the Moon and Mars).

Thorsten Kleine (Institue für Planetologie, University of Münster) and Richard Walker (Department of Geology, University of Maryland) provide a thorough review of the ¹⁸²Hf-¹⁸²W chronometer, a precision timer based on the decay of the short-lived radionuclide ¹⁸²Hf (half-life of only 9 million years) to stable ¹⁸²W. Their paper "Tungsten Isotopes in Planets" covers the basic principles of the chronometer and its use in chondritic meteorites, differentiated meteorites, achondrites, Martian meteorites, the Moon, and Earth. Among the important discoveries made with tungsten isotopic data, we now know timescales of accrection and core formation increased with planetary mass. In their wrap-up, Kleine and Walker discuss the immense value of tungsten isotopes in understanding the origin of the Moon (for example, see PSRD article: Tungsten Isotopes, Formation of the Moon, and Lopsided Addition to Earth and Moon).

 (pdf version)

See Reference:
·   Kleine, T. and Walker, R. J. (2017) Tungsten Isotopes in Planets, Annual Review of Earth and Planetary Sciences, v. 45, p. 389-417, doi: 10.1146/annurev-earth-063016-020037. [ view online ]

See also:
·   Taylor, G. J. (Nov. 2003) Hafnium, Tungsten, and the Differentiation of the Moon and Mars. Planetary Science Research Discoveries. http://www.psrd.hawaii.edu/Nov03/Hf-W.html.
·   Taylor, G. J. (June 2015) Tungsten Isotopes, Formation of the Moon, and Lopsided Addition to Earth and Moon. Planetary Science Research Discoveries. http://www.psrd.hawaii.edu/June15/W-Earth-Moon.html.

Written by Linda M. V. Martel, Hawai‘i Institute of Geophysics and Planetology, for PSRD.