Hf: isotopic composition

Ionov D. A., and Weis D. (2002) Hf isotope composition of mantle peridotites first results and inferences for the age and evolution of the hthospheric mantle. Abstract, 4th Int. Workshop on Orogenic Lherzolites and Mantle Processes, Samani, Japan, pp. 56—57. 

The Lu-Hf isotope composition of cratonic lithosphere disequilibrium between garnet and clinopyroxene in kimberlite xenoliths. Geochim. Cosmochim. Acta 6651, Ain. 

Beard B. L. and Johnson C. M. (1993) Hf isotope composition of late Cenozoic basaltic rocks from northwestern Colorado,... 

Machado N. and Simonetti A. (2001) U-Pb dating and Hf isotopic composition of zircon by laser ablation-MC-ICP-MS. In Laser-Ablation-ICPMS in the Earth Sciences Principles and Applications (ed. P. Sylvester). Mineralogical Association of Canada, Ottawa, pp. 121-146. 

Corfu E. and Stott G. M. (1996) Hf isotopic composition and age constraints on the evolution of the Archean central Uchi Subprovince, Ontario, Canada. Precamb. Res. 78, 53-63. 

PiotrowsM A. M., Lee D. C., Christensen J. N., Burton K. W., HalUday A. N., Hein J. R., and Gunther D. (2000) Changes in erosion and ocean circulation recorded in the Hf isotopic compositions of North Atlantic and Indian Ocean ferromanganese crusts. Earth Planet Sci. Lett 181(3), 315-325. 

Transport balance or box models have been used by many workers in the past in efforts to understand the trace element and isotope characteristics of the Earth s major silicate reservoirs, i.e. continental crust, and upper and lower mantle (e.g. Jacobsen Wasserburg 1979 Zartman Haines 1988). Although simple mass balance calculations can be applied to present-day trace element concentrations and Pb, Nd and Hf isotope compositions of major reservoirs, e.g. continental crust and depleted mantle, to test the hypothesis that these reservoirs are complementary, transport balance models are needed to test ideas on their evolution in time. The reason is that the isotope ratio variations are the result of time-integrated trace element variations in the reservoir, modified by fluxes between them. Below, recent transport balance models in which the evolution of the continental crust is examined using Th-U-Pb (Kramers T olstikhin 1997) and... 

Blichert-Toft and Arndt (1999) proposed an alternative different set of reference values for the BSE. If these were to be adopted, then it is necessary that either the Earth accreted at a different time from the normally accepted 4.57 Ga or from a bulk composition different from that of Cl chondrites. This latter option was explored by Patchett et al. (2004) who found significant variation in the Hf-isotopic composition of chondritic meteorites, indicating that the future resolution of terrestrial Hf-isotope systematics is likely to be found in an appropriate choice of meteoritic parent for the Earth. 

Blichert-Toft, J. and Arndt, N.T., 1999. Hf isotope compositions of komatiites. Earth Planet. Sci. Lett., 171, 439-51. 

J. W., 2001. The Hf isotopic composition of global seawater and the evolution of Hf isotopes in deep Pacifc Ocean from Fe-Mn crusts. Chemical Geology, 178 23-42. 

Unlike the situation for the U-Pb systems, where the enrichment of U over Pb is generally so high that single-collector ICP-MS analysis may suffice, Hf isotopic compositions can only be determined using MC instrumentation with sufficient precision to be of any use. 

The geochronological information that can be obtained from such Hf isotopic analysis is a so-called model age (Figure 9.6), representing the moment at which the zircon would have formed from a reservoir with an Hf isotopic composition similar to the depleted mantle (DM) or chondritic uniform reservoir (CHUR), the latter being a model for the whole Earth. 

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