Zircon U-Pb age and geochemical characteristics of ore-bearing granodiorite porphyry in the Duobuza porphyry copper deposit, Tibet

Abstract The Duobuza deposit is the first porphyry-type copper deposit discovered with giant prospect in the Bangongco metallogenic belt. Geochemical data indicates that the ore-bearing Duobuza granodiorite porphyry is high-K calc-alkaline to shoshonitic and peraluminous composition. The ore-bearing granodiorite porphyry is enriched in large-ion lithophile elements(LILE) such as Rb, K, Th, La, Ce and Sr, and depleted in high-field-strength elements(HFSE) such as Nb, Ta, P, and Ti. The rare-earth element (REE) patterns show enrichment in light REEs relative to heavy REEs. The major, rare-earth, and trace elements of the ore-bearing granodiorite porphyry show characteristics of adakites, formed in an island arc setting. The laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U–Pb age of the ore-bearing granodiorite porphyry is 123.4±1.2 Ma (MSWD = 1.7), which also represents the age of the copper-mineralization. Together with the age data of the early Cretaceous magmatic rocks in the Bangongco–Nujiang suture zone and the middle-northern Gangdese, it indicates that there was bidirectional (northward and southward) subduction of the Bangongco–Nujiang ocean during 120 Ma, and the Duobuza deposit was related to this event.