Constraints on the Petrogenesis and Metallogenic Setting of Lamprophyres in the World-Class Zhuxi W-Cu Skarn Deposit, South China

Whole-rock and apatite geochemical analyses and zircon U-Pb dating were carried out on the lamprophyres in the world-class Zhuxi W-Cu skarn deposit in northern Jiangxi, South China, in order to understand their origin of mantle sources and their relationship with the deposit, as well as metallogenic setting. The results show the lamprophyres were formed at ca. 157 Ma, just before the granite magmatism and mineralization of the Zhuxi deposit. These lamprophyres have from 58.98-60.76 wt% SiO2, 2.52-4.96 wt% K2O, 5.92-6.41 wt% Fe2O3t, 3.75-4.19 wt% MgO, and 3.61-5.06 wt% CaO, and enrichment of light rare earth elements (LREE) and large-ion lithophile elements (LILE), and depletion of high-field-strength elements (HFSE). Apatites in the lamprophyres are enriched in LREE and LILE, Sr, S, and Cl, and have(87)Sr/Sr-86 ratios ranging from 0.7076 to 0.7078. The conclusions demonstrate that the lithospheric mantle under the Zhuxi deposit was metasomatized during Neoproterozoic subduction. Late Jurassic crustal extension caused upwelling of the asthenospheric mantle and consecutively melted the enriched lithospheric mantle and then crustal basement, corresponding to the formation of lamprophyres and mineralization-related granites in the Zhuxi deposit, respectively.