Origin of the Darongshan-Shiwandashan S-type granitoid belt from southeastern Guangxi: geochemical and Sr-Nd-Hf isotopic constraints

Comprehensive geochemical, Sr-Nd isotopic and in-situ zircon Hf isotopic data are reported for the Pubei pluton, the Jiuzhou pluton and the Taima pluton, which consist dominantly of the Darongshan-Shiwandashan granitoid belt in SE Guangxi. Petrographic and element geochemical features show that these plutons are typical S-type granites. High I-Sr > 0.721) and low epsilon(Nd) (t) values (- 13. 0 similar to - 9. 9) indicate that they were originated from evolved crustal materials. Among the 230Ma magmatic zircons, most have a limited range of epsilon(Hf)(t) values between - 11 and - 9 corresponding to T-DM2 ages of ca. 1. 9 - 1. 8 Ga, and the remainder have relatively high epsilon(Hf)(t) values up to - 4. 5 corresponding to younger T-DM2 ages of ca. 1. 5Ga. Inherited zircons in age of 1681 similar to 384Ma have epsilon(Hf)(t) of - 17. 1 similar to + 3. 4, and T-DM2 ages clustering at 2. 4Ga, 1. 9Ga and 1. 5Ga. Considering that most - 230Ma magmatic zircc.ns have epsilon(Hf)(t) values consistent with the estimated values in terms of Hf-Nd isotopic array, we interpret that the crust with average residential time of 1. 9Ga is the dominant material source for the studied granites. Some magmatic and inherited zircons have nearly the same T-DM2 ages of similar to 1. 5Ga, indicating that the crust with average residential time of 1. 5Ga is also involved in formation of these granitoids. Given that no igneous zircons with T-DM2 older than 2.0Ga have been detected, minor amount of recycled crustal materials with average residential time of 2. 4Ga could also be involved. Because new mantle inputs have not been identified in terms of zircon Hf isotopes, mantle-derived magmas might not have been involved in formation of this S-type granitoid belt.