关键词: 浅成热液大规模成矿作用, 成矿结构, 成矿系统, 地球动力学背景, 中国东北部陆缘

Abstract: Epithermal deposits are important sources of nonferrous and precious metals as well as rare and critical metal resources such as indium. Due to their vectors toward deep porphyry mineralization, they have attracted the attentions of global geologists. The continental margin of Northeast China is one of the areas where epithermal ore deposits are widespread, characterized by epithermal Au and Ag-Pb-Zn-Cu polymetallic deposits being occur. According to the deposit geology, these epithermal-type deposits in Northeast China were divided into three types, low-sulfidation type (LS), intermediate-sulfidation type (IS) and high-sulfidation type (HS). The mineralization occurred in the Late Jurassic to Early Cretaceous volcanic basins and uplift areas spatially close to granite complex margins, comprising four separated mineralizationstages as a function of time, including (1) 151 to 141 Ma, (2) 140 to 131 Ma, (3) 123 to 120 Ma, and (4) 110 to 100 Ma. Stage 1 is restricted in the eastern portion of the Great Xing’an Range, characterized by regional epithermal HS copper polymetallic deposits. Stage 2 is developed in the western portion of the Great Xing’an Range, where large-scale epithermal LS-IS Ag-Pb-Zn mineralization. Stage 3 occurs in middle portion between the north of the Great Xing’an Range and the Lesser Xing’an Range and in Yanbian and western Liaoning, characterized by epithermal IS Cu and LS Te-Au mineralization. Stage 4 occurs in the Northern Great Xing’an Range-the Lesser Xing’an Range-Raohe-Dongning-Yanbian area. There is a younger mineralization time from the eastern portion of the Great Xing’an Range-the western portion of the Great Xing’an Range-the northern margin of the North China platform (Liaoxi+Yanbian)-the northern margin of the eastern portion of the Great Xing’an Range (Heihe) to the northern portion of the Great Xing’an Range-the Lesser Xing’an Range-Wanda Mountains-Taiping Mountains-Yanbian. There is a transition in mineralization type, from Cu polymetallic to Ag-Pb-Zn to Cu-Au + Te-Au to Au (± Sb) +large-scale Au and Cu. The tectonic environments for the various mineralization are related to the episodic subduction of ate Mesozoic Paleo-Pacific plate towards the eastern end of Eurasia, in which there is a transition from compressional to crustal extensional conditions. Except the mineralization in the Yanbian area occurring in the late stage of intermediate-basic volcanic eruption-hypabyssal emplacement, the remnant mineralization formed in the late stage of bimodal volcanic eruption-hypabyssal emplacement. Considering the genetic relation between epithermal metallic and porphyry Cu and Mo mineralization, the early-stage epithermal Ag-Pb-Zn-Cu mineralization and the coeval porphyry mineralization constitute the porphyry Mo-epithermal Ag-Pb-Zn system, whereas the epithermal LS Ag-IS Pb-Zn-HS Cu polymetallic and porphyry Cu-Mo mineralization constitute the porphyry Mo-Cu-epithermal Ag-Pb-Zn hydrothermal system. Similarly, the intermediate- and late-stage epithermal Au mineralization and Au-rich porphyry Cu mineralization constitute the Au-rich porphyry Cu-epithermal IS Cu-Au hydrothermalsystem and the Au-rich porphyry Cu-epithermal IS Cu-Au-epithermal HS Au (Cu) hydrothermal system. Nevertheless, more evidence is needed to clarify whether the epithermal LS Te-Au, Sb-Au, and Au deposits are individual ore system or not. Late Mesozoic epithermal ore systems are the results  the underplating of mantle-sourced basaltic magmas and their interactions with lower-crustal magmas during a roll-back of subducting slab and a thinning crust episode from Late Jurassic to Early Cretaceous.

Key words:  , large-scale epithermal mineralization, mineralization frames, ore system, geodynamic setting, continental edge of Northeast China