40Ar/39Ar and Rb‐Sr Ages of the Tiegelongnan Porphyry Cu‐(Au) Deposit in the Bangong Co‐Nujiang Metallogenic Belt of Tibet, China: Implication for Generation of Super‐Large Deposit

Abstract The Tiegelongnan deposit is a newly discovered super‐large porphyry‐epithermal Cu‐(Au) deposit in the western part of the Bangong Co‐Nujiang metallogenic belt, Tibet (China). Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate‐felsic intrusions (ca. 123–120 Ma). Various epithermal ore and gangue mineral types were discovered in the middle‐shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite (potassic zone), sericite (phyllic zone), and alunite (advanced argillic zone) in/around the ore‐bearing granodiorite porphyry yielded 121.1±0.6 Ma (1σ), 120.8±0.7 Ma (1σ) and 117.9±1.6 Ma (1σ), respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb‐Sr dated to be 117.5±1.8 Ma (2σ), representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic‐hydrothermal system. The Tiegelongnan super‐large Cu‐(Au) deposit may have undergone a prolonged magmatic‐hydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.