Jack Hills

Loss of Barth s early atmo.sphcrc lianh s accretion, core fonnation. aJKl desaasing essemially oompkie Farliesl Jack Hills zircon fragment... 

Mojzsis S. J., HarrisonT. M., and Pidgeon R. T. (2001) Oxygen isotope evidence from ancient zircons for liquid water at the Earth s surface 4300 Myr ago Jack Hills, evidence for more very old detrital zircons in Western Australia. Nature 409, 178-181. 

Figure 4 Initial snf values of >3.9 Ga detrital zircons from the Jack Hills, Western Australia (Amelin et al., 1999) and Early Archean Itsaq complex gneisses (Vervoort and Blichert-Toft, 1999). The same data have been recalculated using two recently proposed revisions to the Lu decay constant the closed symbols use the decay constant proposed by Bizzarro et al. (2003). The open samples are calculated using the 6% lower decay constant proposed by Scherer et al. (2001). The present-day chondrite parameters used are Hf/ Hf = 0.282772 and Lu/ Hf = 0.0332 (Blichert-Toft and Albarede, 1997).

Amelin Y. V. (1998) Geochronology of the Jack Hills detrital zircons by precise U-Pb isotope dilution analysis of crystal fragments. Chem. Geol. 146, 25—38. 

Maas R., Kinny P. D., Wilhams 1. S., Froude D. O., and Compston W. (1992) The Earth s oldest known crust a geochronological and geochemical smdy of 3,900-4,200 Ma old detrital zircons from Mt. Narryer and Jack Hills, Western Australia. Geocliim. Cosmochim. Acta 56, 1281-1300. 

Figure 2 Zircon grain, in part 4.3 Ga old (Compston and Pidgeon, 1986). Jack Hills, Western Australia. Scale bar is 100 p,m long.

The oldest known terrestrial materials are 4.1-4.4Ga detrital zircons from the Mount Narryer area of western Australia (Froude et al., 1983). The first locality to be shown to host extremely ancient zircons (4.1-4.2Ga) was a sequence of highly metamorphosed quartzites, conglomerates, and pelites from Mount Narryer, at the northwestern edge of the Yilgarn Craton in western Australia. Subsequent discoveries, in a less metamorphosed sequence of sediments from the Jack Hills, some 60 km away identified even older zircons, some 4.28 Ga old (Compston Pidgeon, 1986). Recently, Wilde et al. (2001) reported a zircon grain with an age of 4.404 0.008 Ga (Fig. 1.10). To date this is the... 

The results of the fast decay scheme (Fig. 3.29b) are similar to the original curve by Vervoort and Blichert-Toft (1999) and imply a very early (pre-3.5 Ga) mantle differentiation event, followed by less extreme mantle depletion. The early depletion event was most likely caused by the production of a very early mafic crust. Thus the ultimate source of the parental magmas of the Jack-Hills zircons, the Amitsoq gneisses, and some Barberton komatiites, was mantle that had already been depleted in the early Archaean. Bizzarro et. al. (2003) proposed that this early differentiation of the mantle took place prior to 4.33 Ga. This result is consistent with evidence from 142Nd for a very early mantle melting event, as outlined in the previous section of this chapter. 

A, zircons from Amitsoq Gneisses, west Greenland B [black squares], komatiites and basalts from Barberton Greenstone Belt, South Africa JH, zircons from the Jack Hills,... 

Compston, W. and Pidgeon, R.T., 1986. Jack Hills, evidence of more very old detrital zircons in western Australia. Nature, 321, 766-9. 

MennekenM, NemchinAA, GeislerT, Pidgeon RT, Wilde SA Hadean diamonds in zircon from Jack Hills, Western Australia. Nature 2007, 448(7156) 917— 920. 

Begins her first extant diary (3 January). Half-sister Stella Duckworth marries Jack Hills (10 April), but dies soon afterwards (19 July). Begins classes in Greek and History at King s College, London (November). 

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