Geochronology of the Magmatic Rocks in the Duobaoshan Porphyry Cu-Mo Deposit in the Great Xing’an Range: Implication for the Metallogenic Epochs and Related Geodynamics

The Duobaoshan porphyry copper–molybdenum deposit is located in the Great Xing’an Range, eastern segment of the Xing-Meng orogenic belt. It is the largest porphyry Cu-Mo deposit in NE China. Based on the contact relations of intrusive rocks and the results of LA-ICP-MS zircon U-Pb ages, we found that there were five stages of magmatism in the mining area, including the Early Ordovician (478.1 ± 3.2 Ma) granodiorite, the Middle Ordovician (462.1 ± 3.3 Ma, 459.5 ± 2.3 Ma) granodiorite porphyry, the Late Triassic (226.3 ± 0.4 Ma) oligoclase granite, the Middle Jurassic (170.1 ± 5.6 Ma) andesitic porphyrite, and the Early Cretaceous (118.1 ± 6.6 Ma) diorite. The Early and Middle Ordovician granodiorite and granodiorite porphyry are the principal host rocks for the mineralization in the deposit. However, Cu-Mo mineralization was also observed within the Late Triassic oligoclase granite, indicating that there are two stages of Cu-Mo mineralization in the Duobaoshan deposit. Combined with the previously reported Late Triassic skarn Cu mineralization occurring in the Xiaoduobaoshan deposit, and the Early Jurassic skarn Cu mineralization in the Sankuanggou and Yubaoshan deposits, we conclude that there are four metallogenetic stages in the Duobaoshan ore-concentration area. Regionally, there are five stages of Cu-Mo mineralization occurring in the northern Great Xing’an Range, including the Ordovician, Late Triassic, Early Jurassic, Late Jurassic, and Early Cretaceous. After discussing the tectonic setting for the generation of these deposits, we propose that the Duobaoshan ore-concentration area was influenced by the subduction of the Paleo-Asian Ocean, Mongol-Okhotsk, and Paleo-Pacific Plates during the Phanerozoic.