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Science 26 May 2006:
Vol. 312. no. 5777, p. 1139
DOI: 10.1126/science.1125301
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Technical Comments

Comment on "Heterogeneous Hadean Hafnium: Evidence of Continental Crust at 4.4 to 4.5 Ga"

John W. Valley1*, Aaron J. Cavosie1{dagger}, Bin Fu1, William H. Peck2 and Simon A. Wilde3

1 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.
2 Department of Geology, Colgate University, Hamilton, NY 13346, USA.
3 Department of Applied Geology, Curtin University, Perth, WA, Australia.


Figure 1 Fig. 1. Zircons 01JH54-77 and -81 from Jack Hills metaconglomerate showing sites of U-Pb analyses with age. Ages are in Ma and are >90% concordant. Scale bars, 50 µm. Additional analyses are shown in figure 5 in (2). [View Larger Version of this Image (66K GIF file)]
 

Figure 2 Fig. 2. Histograms for average Ti-in-zircon temperatures for individual zircons from kimberlite; mafic and ultramafic; felsic and intermediate composition rocks; and >4 Ga Jack Hills detrital zircons. Lithologic subsets of these groupings are more limited in range. For instance, Grenville anorthosites and gabbros average 720 ± 37°C (n = 47). From (12). [View Larger Version of this Image (18K GIF file)]
 

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