Metallogenic characteristics and prospecting indicators of Nb-REE polymetallic deposits in Hulunxibai area, Inner Mongolia

In recent years, many Nb-REE deposits (ore spots) have been discovered in Hulunxibai area on the eastern margin of Beishan metallogenic belt. The deposits (ore spot) occur in the external contact zone of Permian adamellite, and the orebodies occur in the littoral-shallow marine carbonate and metamorphic detrital rocks. The morphology, attitude and scale of the orebody are controlled by tectonic-magmatic activity, and orebody position is consistent with the magnetic anomaly. The Nb₂O₅ grade of northeast Huishi Mountain mining area is generally between 0.02% and 0.56%, with an average of 0.11%, and the REO grade is between 0.13% and 2.63%, with an average of 0.93%. The Nb₂O₅ grade of the west Huisenwula mining area is between 0.01% and 0.1%. The metallogenic type is similar to that of the superlarge Nb-REE-Fe deposit in Bayan Obo. The metallogenic potential of NbREE deposits in this area is enormous. Combined with regional geological setting and metallogenic characteristics of the Nb-REE polymetallic mineralization zone, the authors hold that prospecting indicators for this type of Nb-REE polymetallic deposits in this area are as follows:ⅰ. Permian littoral-shallow marine carbonate and metamorphic detrital rocks strata; ⅱ. free space or transfer sites between ductile and brittle deformation from the tectonic compression; ⅲ. Permian adamellite outer contact zone; ⅳ. aeroradiometric anomaly gradient zone and magnetic anomaly; ⅴ. wall-rock alteration (limonitization, silicification, carbonatization, etc); ⅵ. fine quartz network veins development area. The study of the metallogenic characteristics and prospecting indicators of the Nb-REE polymetallic deposits in this area is helpful to promoting the prospecting ideas of rare earth, rare metal and rare-scattered elements mineral resources in Beishan area, and can also provide a reference for the prospecting direction of such deposits.