Tectonic setting of Triassic magmatic and metallogenic event in the Duobaoshan mineralization area of Heilongjiang Province, 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 +/- 2.3Ma, 235.4 +/- 2.7Ma, 226.6 +/- 1.7Ma and 232.8 +/- 1.7Ma, respectively. In addition, the Re-Os model age of molybdenites from the Tongshan porphyritic granite is 229.4 +/- 3.5Ma. 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. Copyright (c) 2015 John Wiley & Sons, Ltd.