Hafnium isotope

The Mossbauer effect has been observed in the following four hafnium isotopes I76jjf I77jjf I78jjf isojjf jj lear transitions of 88.36, 112.97, 93.2,... 

Figure 6.2 Mass spectrum of hafnium isotopes measured by double-focusing sector field ICP-MS.

Figure 7 Hafnium isotopic compositions for in-house Ames Hf standard and international standard JMC-475 as measured on the VG Elemental Plasma 54 (P54) at the University of Michigan. (From Halliday et al., 1998b.)...

Ballentine, C. J., Lee, D-C., and Halliday, A. N. (1997) Hafnium isotopic studies of the Cameroon line and new HIMU paradoxes. Chem. Geol. Hofmann Volume, 139, 111-124. 

Thirlwall, M.F., and Walder, A.J. (1995) In situ hafnium isotope ratio analysis of zircon by inductively coupled plasma multiple collector mass spectrometry. Chem. Geol. 122, 241-247. 

In 2005, De Laeter discussed the role of isotope reference materials for the analysis of non-traditionaT stable isotopes. At present, no isotopically certified reference materials exist for a large number of elements, including Cu, Zn, Mo and Cd, and it is important that this situation be rectified as soon as practicable. Before the isotopically certified reference materials become available for selected elements, suitable reference materials can be created as a standard if sufficient and reliable isotope data have been obtained by interlaboratory comparisons. For example, the Hf/ Hf isotope ratio was measured using hafnium oxide from Johnson Matthey Chemicals, JMC-475, for hafnium isotope ratio measurements with different multi-collector mass spectrometers (ICP-MS and TIMS) as summarized in Table 8.1. However, no isotope SRM is certified for the element Mo either. Mo isotope analysis is relevant, for example, for studying the isotope fractionation of molybdenum during chemical processes or the isotope variation of molybdenum in nature as the result of the predicted double (3 decay of Zr or 18.26-28 spectroscopically pure sample from Johnson Mattey Specpure is proposed as a laboratory standard reference material if sufficient and reliable isotope data are collected via an interlaboratory comparison. 

It has been recognized that the Lu-Hf isotopic system in zircon is a powerful tool for deciphering the evolution of the earth s crust and mantle. " Zircon normally contains 0.5-2 wt % Hf, which results in an extremely low Lu/Hf ratio (" Lu/" Hf < 0.002) and consequently a negligible radiogenic growth of Hf due to the decay of Lu. Therefore, the Hf/" Hf ratio of zircon can be regarded as the initial value at the time when it crystaUized. LA-ICP-MS with a multiple ion collector system has also been employed to study the hafnium isotopic composition of zircon and baddeleyite standards in U-Pb geochronology. °°... 

With these caveats, one can deduce the following. Early single grains appear to have recorded hafnium isotopic compositions that provide evidence for chondritic or enriched reservoirs. There is no evidence of depleted reservoirs in the earliest (Hadean) zircons dated thus far (Amelin et al., 1999). Use of alternative values for the decay constants or values for the primitive mantle parameters increases the proportion of hafnium with an enriched signature (Amelin et al., 2000), but does not provide evidence for early mantle depletion events. Therefore, there is little doubt that the Hadean mantle was extremely well mixed. Why this should be is unclear, but it probably relates in some way to the lack of preserved continental material from prior to 4.0 Ga. 

Nature of the Earth s earliest crust from hafnium isotopes in single detrital zircons. Nature 399, 252-255. 

Another important observation is that, while strontium, neodymium, and hafnium isotopes all correlate with each other, they form poorer, but still signihcant, correlations with ° Pb/ °" Pb (or... 

Unlike. 208pb/204pb or 2 pb/204pb, which depend on Th/Pb and U/Pb, respectively, 208p 5 /206p]3 reflects the Th/U ratio integrated over the history of the Earth. The existence of global correlations between neodymium, strontium, and hafnium isotope ratios and, and the absence... 

Radiogenic isotope ratios of OIE are shown on Figure 15. These diagrams display remarkably similar topologies as the respective MORE data shown in Figures 4-6. Strontium isotope ratios are negatively correlated with neodymium and hafnium isotopes, and correlations between strontium, neodymium, and hafnium isotopes and lead... 

Implications of Neodymium and Hafnium Isotopic Evolution Curves Episodic Mantle Evolution ... 

As described in Section 2.13.2.4, there has been, and continues to be, much debate over the veracity of the highly positive isotopic compositions observed in >3.6 Ga rocks. Lute-tium and hafnium are sited in different phases than are samarium and neodymium, such that metamorphism and alteration should affect each isotopic system differently. One motivation for much of the hafnium isotopic work on Archean... 

Amelin Y., Lee D. C., and Halliday A. N. (1999) Nature of the Earth s earliest crust from hafnium isotopes in single detrital zircons. Nature 399, 252-255. 

Bizzarro M., Baker J., Haack H., Ulfbeck D., and Rosing M. (2003) Early history of the Earth s crust-mantle system inferred from hafnium isotopes in chondrites. Nature 421, 931-933. 

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