Zircon LA-ICP-MS U-Pb dating of gabbro of the Banpo Pt-Pd-polymetallic deposit in Jinggu, Yunnan Province, and its geological significance

Abstract：The Banpo Pt-Pd Complex Deposit of Jinggu is located in Lanping-Simao landmass along the southern part of the Lancang River. Its mineralization is related to Banpo complex. This complex mainly consists of mafic-ultramafic rocks such as peridotite, pyroxenite, gabbro, gabbro diorite and diorite. U-Pb age of zircons from the gabbro determined by LA-ICP-MS is 302.6±2. 0 Ma, indicating that Banpo Complex was formed in Late Carboniferous. The gabbro belongs to high aluminum basite. The rock samples are all characterized by slight enrichment of light rare earth elements relative to heavy rare earth elements, the enrichment of ion lithophile elements (Rb, Sr, K, Ba) and the depletion of high field strength elements (Nb, Ta, Zr and Hf). These characteristics are typical of island arc magmas and indicate that Banpo complex was formed in an island-arc environment related to plate subduction. Therefore, southern Lancang River is considered to have been an oceanic island arc subduction belt between the late period of Late Carboniferous and the early period of Early Permian.