Abstract: The Erdaokan Ag-Pb-Zn deposit is a large Triassic Ag-Pb-Zn deposit newly discovered in the Duobaoshan metallogenic belt, Heilongjiang Province. Till now, little research has been conducted on  its formation mechanism, and its genesis is not clear yet. We selected the hydrothermal rhodochrosite as the research object, and systematically studied its mineralogical properties and geochemical characteristics by using optical microscope and LA-ICP-MS dating. The results show that the rhodochrosite is characterized by strong negative Eu anomaly and positive Ce anomaly, enrichment of light rare earth elements, and depletion of heavy rare Earth elements. In addition, the fractionation degree of light rare Earth elements  is significantly higher than that of the heavy rare earth elements, showing an overall right REE  distribution curve. On this basis，it is considered that the rhodochrosite in the Erdaokan Ag-Pb-Zn deposit was formed in a reducing environment, and the ore-forming materials  came from mixed sources. The deep ore-forming materials from the mantle, the carbonaceous shale and limestone near the ore all have important contributions to the formation of rhodochrosite.

Key words: Duobaoshan metallogenic belt, Erdaokan Ag-Pb-Zn deposit, rhodochrosite, geochemistry