关键词: 灵山岛, 岩石成因, 锆石U-Pb测年, Hf同位素, 后碰撞伸展

Abstract: In this study, we conducted systematically zircon U-Pb dating of two representative rhyolite samples from the Lingshan
Island in Qingdao, Shangdong Province. The results show that the weighted ages of two rhyolite samples are ca. 123.1±1.9 Ma and 121.4±
1.4 Ma. These two ages are consistent within the uncertainty, representing the formation and crystallization age of the rhyolite.
Geochemically, the rhyolite samples show high contents of SiO2 and Na2O+K2O, while they are characterized by low contents of P2O5 TiO2
and CaO, as well as low Mg# values. In addition, the rhyolite samples are enriched in LILEs (Rb, Th and K) and LREEs, but depleted in
HFSEs (e.g. Nb, Ta, Ti and P). Rock assemblages, geochemical features, and low whole-rock Zr saturation temperatures indicate that the
rhyolites belong to highly-fractionated I-type rhyolite rather than A-type rhyolite in an extensional setting, and are products of
post-collisional magmatism. The zircon εHf(t) values range from -27.2 to -32.3, and the sencond stage model ages are between 2662 and
3167 Ma, indicating that the rhyolite was origanited from partial melting of ancient crust. The presence of Neoproterozoic inherited
zircons indicates that it was originated from partial melting of the Yangtze middle-crustal material. These results suggest that the
destruction of North China Craton (NCC) was the cause, leading to large-scale partial melting of the Yangtze crustal material. The
regional extensional tectonics related to the destruction of NCC provided emplacement space for the rhyolite in the last stage.

Key words: Lingshan Island, petrogenesis, Zircon U-Pb dating, Hf isotope, post-collisional extension