Genesis of the monzonitic granite in wangjiadian, Huadian, Jilin province, China: constraints from whole-rock geochemistry, zircon U-Pb geochronology, and Hf isotopes

Abstract

The Huadian area in Jilin Province records multiple tectonic phases from the Paleozoic to the Mesozoic, which have generated a complex geological framework. However, Jurassic magmatic rocks are extremely scarce in this region, resulting in a significant gap in the geological record for this critical period. This study presents integrated geochemical, zircon U-Pb geochronology, and Hf isotopic data for the Wangjiadian monzonitic granite. The intrusion yields an emplacement age of 185.1 ± 2.1 Ma, corresponding to the Early Jurassic. Geochemically, it is characterized by high SiO 2 (73.60-74.28 wt%), elevated alkali contents (Na 2 O+ K 2 O = 7.71-8.24 wt%), and high Al 2 O 3 (13.28-13.62 wt%), but is relatively depleted in MgO (0.18-0.21 wt%) and CaO (0.70-0.73 wt%). It exhibits strong enrichment in light rare earth elements (LREEs), a slightly moderate negative Eu (δEu = 0.65–0.79), and typical geochemical features of high-K calc-alkaline I-type granites. Trace element patterns display enrichment in LREEs, Rb, Th, U, and K, coupled with depletions in Sr, P, and Ti. The Hf isotopic compositions (ε Hf (t) = −10.98 to −4.61; t DM2 (Hf) = 1,518–1915 Ma) indicate that the magma was generated by partial melting of Paleoproterozoic crustal basement at lower crustal levels. In combination with coeval Early Jurassic granites in the upper Yanji area and bimodal magmatism in the Xiaoxing’anling-Zhangguangcai Ridge, these results suggest northwestward subduction of the Paleo-Pacific Plate beneath the northeastern margin of the Sino-Korean Block during the Early Jurassic.