U-Pb single-zircon and Sm-Nd whole-rock isotopic data for the Tanghu Granite of the Zhuguangshan batholith suggest that a basement either composed of or derived from Middle Proterozoic to Late Archean rocks underlies southeast China The granite contains two kinds of inherited zircon components, whole anhedral zircons and small cores within younger magmatic zircons. The U-Pb data for a single analysis of four magmatic zircons yielded a concordant age of 433 ±2 Ma, whereas single zircons yielded two linear arrays with lower intercepts of 435 ±1 and 434 ±14 Ma and upper intercepts of 1415 ±3 and 2516 ±6 Ma, respectively. Xenocrystic zircons of Archean age had not previously been recognized in any rocks from southeast China Two whole-rock samples from the granite yielded ϵNd values of -7.1 and -8.3 at 434 Ma and Nd model ages of ∼1750 Ma relative to a depleted mantle. We conclude from this isotope data that the Tanghu Granite crystallized at 434 ±1.6 Ma (weighted average) and was derived from a source of unknown age, but had an average crustal-residence age of ∼1750 Ma, and was partially composed of a mixture of continental crustal material of at least two ages (∼1400 and ∼2500 Ma).

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