Petrogenesis and tectonic significance of the Lianhuashan intrusion in the western Yunnan: Constraints from zircon U-Pb geochronology, bulk element composition and Sr-Nd-Pb-Hf-O isotopic compositions

　　The Cenozoic potassic magmatic belt in western Yunnan is exposed along the Jinshajiang-Ailaoshan suture zone and is associated with numerous mineral deposits. It has become a focal area for geologists studying Cenozoic magmatism, metallogeny, and lithospheric architecture. The Lianhuashan intrusion, located at the western edge of this potassic magmatic belt and on the southeastern margin of the Lanping Basin in the northern Indo-China Block, holds significant tectonic implications. Typical quartz monzonite was sampled from the Lianhuashan pluton and systematic zircon U-Pb geochronology, Hf-O isotope analysis, whole-rock geochemistry, and Sr-Nd-Pb isotopic studies were conducted in this study. The results indicate that the Lianhuashan intrusion formed at 36.3 Ma. The quartz monzonites show shoshonitic affinity, characterized by high alkali and potassium contents, enriched in large ion lithophile elements such as Rb, Pb, and Sr, and depleted in high field strength elements like Ta and Zr, with distinct Nb-Ta-Ti negative anomalies. The ɛ_Hf(t) values range from +2.74 to +4.77, δ¹⁸O values from 7.76 to 9.04‰, and ɛ_Nd(t) values from -3.92 to -3.76, suggesting that the initial magma source was the lithospheric mantle metasomatized by the subduction of the Paleo-Tethys Ocean. Its formation is related to lithospheric delamination caused by the thickening of the lithosphere due to the Indian-Asian continental collision, representing a response to delamination processes within the Indo-China Block.