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The Tongshan porphyry Cu-Mo deposit is located in the northeast segment of the Xing'an-Mongolia Orogenic Belt, and the west of the Hegenshan-Heihe fault which is the boundary of the Xing'an Block and the Songnen Block. It represents the typical Early Paleozoic porphyry Cu-Mo mineralization (Zhao et al., 1997;Liu et al., 2010;Zeng et al., 2014) and provides good examples for the scientific research on such type of ore deposits in NE China.

The Duobaoshan mineralization area is located in the northeast part of the Xing'an-Mongolia orogenic belt which belongs to the eastern part of the Central Asian Orogenic Belt (CAOB). This region has experienced multiple tectonic-magmatic-metallogenic events that resulted in a number of large-superlarge mineral deposits, e.g. the early Palaeozoic Duobaoshan and Tongshan porphyry Cu-Mo deposits, the early Mesozoic Sankuanggou skarn Fe-Cu deposit and Xiaoduobaoshan skarn Cu deposit and the late Mesozoic Zhengguang epithermal Au deposit. By detailed field survey, we have examined the weak alteration and mineralization in the tonalite veins intruding early Palaeozoic ore-bearing granodiorite in the Duobaoshan deposit and the veinlet-disseminated Cu-Mo mineralization in the porphyritic granite veins intruding in the ore-hosting Ordovician strata of the Duobaoshan Formation in the Tongshan deposit. Zircon grains from the Duobaoshan tonalite, the Tongshan porphyritic granite, and the metallogenic granite porphyry and the granodiorite in the Xiaoduobaoshan deposit yield LA-ICP-MS U-Pb weighted mean ages of 230.9 ± 2.3 Ma, 235.4 ± 2.7 Ma, 226.6 ± 1.7 Ma and 232.8 ± 1.7 Ma, respectively. In addition, the Re-Os model age of molybdenites from the Tongshan porphyritic granite is 229.4 ± 3.5 Ma. Those isotope dating results indicate that the Duobaoshan mineralization area experienced the Triassic magmatic-mineralization event. Considering the regional tectonic history of the area and the fact that the major and trace element characteristics of the Triassic tonalite in the Duobaoshan deposit are similar to those of island-arc type igneous rocks, it is presented that the Triassic magmatic-metallogenic event might be closely related to the subduction of the Mongolia-Okhotsk plate, and that the metallogenic elements originated from the mantle wedge metasomatized by liquid of subduction oceanic slab. Previous research and new geochemical analyses presented in this study indicate that the Duobaoshan mineralization area experienced at least four epochs of magmatic-metallogenic events including the Ordovician, the Triassic, the Early Jurassic and the Late Jurassic to Early Cretaceous.

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The Gaogangshan Mo deposit, located in the northern part of the Lesser Xing'an Range (the eastern part of the Xing'an-Mongolia Orogenic Belt), is one of the newly discovered Mo deposits in northeast China. Ore bodies occur in the granite and are generally in vein and stockwork forms. Major metallic minerals in the ore include pyrite and molybdenite. The styles of mineralization are disseminated, veinlet-disseminated, and veinlet. The major types of wall-rock alteration are silicification-potassic alteration, phyllic alteration and propylitization. Fluid inclusion analyses indicate that the ore-forming fluid during the major mineralization stage is an H2O-NaCl-CO2 system, with wide homogenization temperature and salinity ranges. The abundant CO2-rich and coexisting halite-bearing fluid inclusion assemblages in the main stage of mineralization highlight the significance of intensive fluid boiling for porphyry Mo mineralization. Comprehensive study of the ore-forming conditions, geological features of the deposit, micro-thermometric analysis of fluid inclusions and comparison of the Gaogangshan deposit with other typical porphyry deposits leads to the conclusion that the deposit is a porphyry type. We obtained a weighted mean age of the molybdenite deposit at Gaogangshan of 250.7 ± 1.8 Ma. The isotopic dating results indicate that the Gaogangshan deposit was formed in the Permo-Triassic, which is the earliest Mo-only deposit in northeast China. The formation of the Gaogangshan Mo deposit may be related to the extension and break-up of the Songnen Block and Jiamusi Block in the Permo-Triassic.