Geochronology and Petrogenesis of the Early Paleozoic Jilongjie Granites in the Central South China Block: Implication for Post-Kinematic Lithospheric Delamination

Controversy over the geodynamic interpretation of the early Paleozoic granites in the South China Block constrains understanding of tectonic-magmatic evolution. In this paper, we present zircon U-Pb age, Hf isotope, and major and trace element data of the early Paleozoic granites in the Jilongjie region, south-central Hunan Province. A sample that yielded a weighted average Pb-206/U-238 age of 425 & PLUSMN; 3 Ma falls into the post-collisional granite field in the classification discriminant of magmatic rocks. Geochemical features indicate that the Jilongjie pluton is a shoshonitic metaluminous rock. The Jilongjie pluton's chondrite-normalized rare earth element patterns exhibit a slight enrichment of light rare earth elements (LREEs) relative to heavy rare earth elements (HREEs) with (La/Yb)(N) ratios of 15.1-23.7 and weak Eu anomalies (Eu/Eu* = 0.68-0.78). Zircon Hf isotope results show & epsilon;(Hf)(t) ranging from -9.94 to -0.69. Jilongjie granite's parent magma originated from a mixing of crust-derived felsic and mantle-derived mafic magmas, which then underwent fractional crystallization during its ascent. Jilongjie granite was generated through a post-collisional extensional setting associated with delamination of the thickened lithosphere.

Automated summary

In this study, the early Paleozoic granites in the Jilongjie region, south-central Hunan Province, were analyzed using zircon U-Pb age, Hf isotope, and major and trace element data. The results suggest that these granites belong to the post-collisional granite type with alkaline metaluminous characteristics. The geochemical features reveal the enrichment of light rare earth elements and weak Eu anomalies. The zircon Hf isotope results indicate a mixture of crust-derived felsic and mantle-derived mafic magmas as the parent magma for the Jilongjie granite, which underwent fractional crystallization during ascent. The formation of Jilongjie granite is associated with post-collisional extensional setting and delamination of the thickened lithosphere.