Abstract: Fig.1 and Fig.2 show the distribution of the available Nd isotopic data of about 240 granite plutons in South China. The majority of depleted mantle model ages of granites range between 1.0-2.0 Ga, with an average of 1.5Ga. The TDM ages of granites are consistent with the ages of the exposed Precambrian basement metamorphic rocks. The massive TDM values strongly indicate that the bulk of South China was formed during the Proterozoic. The majority of εNd(t) range between -5 and -10. The low ε Nd values require an ancient light rare earth element enriched source, as expected for rocks derived from Precambrian continental crust. Consequently the source materials for granites in South China interior are suggested to be dominated by old and recycled crust. One approach towards extracting further information on the source composition from the granites derived from the crustal source is to compare their isotopic composition to the values for exposed, weakly metamorphosed, Proterozoic crust. Field relationships suggest that granites of South China interior are intrllsives with respect to their immediate wall rocks and therefore must have been generated at greater paleo-crustal depths than that represented by the current levels of exposure. Because these granites were generally emplaced at depths between 5 and 15 km, it is probable that the granites derived from the crustal source represent mid crustal melting and so their isotopic composition should provide information regarding the crustal compositions at this depth. The correspondence of Sm-Nd isotopic composition between the granites derived from the crustal source and the exposed weakly metamorphosed Proterozoic crust (Fig.3-7) raves that there is an intermediate to felsic composition crust at mid-crustal depth through out South China interior, and the composition of mid-crustal has not significantly changed from the early Paleozoic to the Mesozoic. However, differentiation of the Nd which magma could result in fractionation of Sm from Nd which is an important factor in controlling the production of lithophile mineralization.