| Summary: | The Bagaladong Pb-Zn deposit is located in the eastern segment of the Gangdese back-arc uplift belt and lacks enough study with no available ages for ores and rocks. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) zircon U-Pb dating and in situ trace elements were carried out for mineralization-related biotite granite in the Bagaladong Pb-Zn deposit and are reported in this paper. The crystallization temperatures of zircons in the biotite granite are obtained by using the zircon Ti thermometer. Trace element composition of zircons in the biotite granite indicates a magmatic origin. Fourteen zircons yield a weighted average 206Pb/238U ages of 129.1±2.3 Ma (MSWD=1.5), suggesting that the biotite granite was established in the middle of the Early Cretaceous, which is consistent with the age of magmatic intrusions obtained by previous studies. Zircon has ΣLREEs values of 13.21-530.28 μg/g with an average of 61.90 μg/g and ΣHREEs values of 849.16-3981.54 μg/g with an average of 1826.91 μg/g. Zircon has left-inclined REEs patterns with relative LREEs depletion and HREEs enrichment. These zircons have δCe and δEu values of 1.20-701.77 and 0.01-0.12, respectively, indicating obviously positive Ce anomalies and negative Eu anomalies. Zircons have Ti contents varying from 0.60 to 7.40 and crystallization temperatures of 593.9-795.3℃ with an average of 724.3℃, which partially reflect the diagenetic temperature. It can be concluded that the Bagaladong biotite granite was probably formed during the extrusion stage of collision after the closure of the Bangong Co-Nujiang ocean basin. The age of the biotite granite in the Bagaladong deposit represents the upper limit of the metallogenic epoch and provides important evidence for prospecting the Early Cretaceous Pb-Zn mineralization in the east section of the Gangdese back-arc fault uplift area.
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