England batholith, NSW, Australia: age implications for the crust

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Zircon Lu-Hf istopic data for representative plutons from the
five granite suites of the New England Batholith indicates a significant
Late Proterozoic lower crustal input for all except one of the
suites. Earlier published oxygen (O’Neil et al.) and recently published
Li isotopic data (Bryant et al., 2004) support the view that
the two Permo-Carboniferous suites (Bundarra and Hillgrove) are
S-type but with 87Sr/86Sr ratios that are lower than those of
Lachlan Fold Belt S-types and that of the three Permo-Triassic
metaluminous suites, one, the Clarence River, is an isotopically
primitive I-type, one, the Moonbi, is a more evolved I-type and
the third, the Uralla, has isotopic and mineralogical characteristics
transitional between I-type and S-type.
New 176Hf/Hf177 data from single zircon grains obtained using
the methods and elegant correction procedures in Griffin et al.
(2000) show that only the Clarence River suite has TDM model
ages close to the emplacement ages. Zircon data for the other four
suites suggests the crustal component underlying of the New England
Batholith could be as old as Late Proterozoic. The data are
consistent with the initiation of the Tasman Fold Belt System, of
which New England is part, around 830 and 730 Ma.

References
Bryant, C.J., Chappell, B.W., Bennett, V.C., McCulloch, M.T., 2004.
Trans. Roy. Soc. Edin. 95, 199–214.
Griffin, W.L., Xiang Wang, Jackson, S.E., Pearson, N.J., O’Reilly, S.Y.,
Xisheng Xu, Xinmin Zhou, 2000. Lithos 61, 237–269.
O’Neil, J., Shaw, S.E., Flood, R.H., Contrib. Mineral Petrol. 62 313–328.