Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics

@article{Mnker2003EvolutionOP,
  title={Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics},
  author={Carsten M{\"u}nker and J{\"o}rg A. Pf{\"a}nder and Stefan Weyer and Anette B{\"u}chl and Thorsten Kleine and Klaus Mezger},
  journal={Science},
  year={2003},
  volume={301},
  pages={84 - 87}
}
It has been assumed that Nb and Ta are not fractionated during differentiation processes on terrestrial planets and that both elements are lithophile. High-precision measurements of Nb/Ta and Zr/Hf reveal that Nb is moderately siderophile at high pressures. Nb/Ta values in the bulk silicate Earth (14.0 ± 0.3) and the Moon (17.0 ± 0.8) are below the chondritic ratio of 19.9 ± 0.6, in contrast to Mars and asteroids. The lunar Nb/Ta constrains the mass fraction of impactor material in the Moon to… 

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References

SHOWING 1-10 OF 23 REFERENCES

Rutile-bearing refractory eclogites: missing link between continents and depleted mantle

Trace element compositions of minerals in xenolithic eclogites derived from cratonic lithospheric mantle show that rutile dominates the budget of Nb and Ta in the eClogites and imparts a superchondritic Nb/Ta, N b/La, and Ti/Zr to the whole rocks.

Fluid- and melt-related enrichment in the subarc mantle: Evidence from Nb/Ta variations in island-arc basalts

The single most distinctive feature of volcanic rocks from convergent-margin settings is a marked depletion of the high field strength elements (HFSE) Nb, Ta, and Ti relative to large ion lithophile

Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf–W chronometry

It is concluded that core formation in the terrestrial planets and the formation of the Moon must have occurred during the first ∼30 million years of the life of the Solar System.

A short timescale for terrestrial planet formation from Hf–W chronometry of meteorites

Measurements of tungsten isotope compositions and hafnium–tungsten ratios of several meteorites indicate that the bulk of metal–silicate separation in the Solar System was completed within <30 Myr, completely consistent with other evidence for rapid planetary formation.

Origin of the Moon in a giant impact near the end of the Earth's formation

This work reports a class of impacts that yield an iron-poor Moon, as well as the current masses and angular momentum of the Earth–Moon system, and suggests that the Moon formed near the very end of Earth's accumulation.