Baoshan Liu

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.

Fe-Mn carbonate is the dominant mineral in the Erdaokan Ag deposit, which represents the first large independent silver deposit during the Late Triassic Period in the Duobaoshan Cu-Mo-Au mineralization concentrated area of Heilongjiang Province, NE China. The Fe-Mn carbonates in the deposit frequently co-exist with Ag minerals. Thus, the presence of Fe-Mn carbonates plays a crucial role in the ore-formation process, making their analysis essential for obtaining valuable metallogenic information about the Erdaokan deposit. Through microexamination, SEM and EDS analysis, a clear relationship between Fe-Mn carbonate minerals and Ag minerals was established. Furthermore, electron probe microanalysis, LA-ICP-MS, and Sr-Nd isotope tests were conducted to analyze Fe-Mn carbonates for significant metallogenic insights. The distribution pattern of trace elements and rare-earth elements in Fe-Mn carbonates is similar, characterized by Zr depletion (below 0.131 ppm), enrichment of light rare-earth elements, a noticeable deficit of Eu (δEu = 0.06–0.63), and an average Y/Ho value of 34.29, indicating the involvement of upper mantle-derived deep magma in the formation of ore-forming materials. The samples had a Sm-Nd isochron age of 233.7 ± 1.2 Ma, suggesting that the Erdaokan Ag deposit was formed during the Late Triassic Period. This study highlights the significance of Fe-Mn carbonate as a valuable mineral indicator for regional silver prospecting purposes, and confirms the Late Triassic Period as another important metallogenic stage in the Duobaoshan Cu-Mo-Au mineralization concentrated area.