Sr-Nd and zircon Hf-O isotopic constraints on the petrogenesis of the orebearing granitic porphyry at Lengshuikeng, Jiangxi Province

The Lengshuikeng lead-zinc deposit in Jiangxi Province is a typical deposit in the northern section of the Wuyi metallogenic belt. The zircon SHRIMP U-Pb age of the ore-bearing granite porphyry in the mining area is (162.0±2.0) Ma. The granite porphyries are highly evolved, with high SiO₂ (69.46%~75.52%), high K₂O (K₂O/Na₂O>3.22) and strong peraluminous (ASI=1.20~1.96). The negative Eu anomalies of the rock mass are relatively strong, and enriched in LILE such as Rb, Th, and U, while the HFSE such as Ba, Sr, Nb, Ta, P, and Ti are depleted. In this study, the authors also report Sr-Nd and zircon Hf-O isotopic compositions of the granitic porphyries at Lengshuikeng. The results show that the granitic porphyries have relatively high initial ⁸⁷Sr/⁸⁶Sr ratios (0.74005~0.76518) and negative εNd values (-11.48~-10.78) as well as the zircon Hf-O isotope measurement value. The variation range of ¹⁷⁶Hf/¹⁷⁷Hf values (0.282317~0.282460) is small, with negative εHf(t) values (-12.39~-7.62) and relatively high δ¹⁸O values (7.23‰~8.81‰), indicating that the magma mainly came from the mature crust, which may have originated from metamorphic basement of North Wuyi area, and the source rocks were probably the metamorphic basement. The magmatic activity was probably related to the crust melting under the compressive background formed by northwestward subduction of the Paleo-Pacific Plate.