Genesis of the Huanggangliang Fe-Sn polymetallic deposit in the southern Da Hinggan Range, NE China: Constraints from geochronology and cassiterite trace element geochemistry

The Huanggangliang Fe-Sn deposit is located in the southern Da Hinggan Range (NE China), and it's one of the most important deposits within the Huanggangliang-Ganzhuermiao Sn polymetallic metallogenic belt. Nearly 90% of the orebodies (stratiform/lenticular) at Huanggangliang are hosted in the Lower Permian andesite or marble. Three ore deposit types were proposed, including: 1) stratabound skarn-type (Yanshanian); 2) exhalative sedimentary (SEDEX)-type (Hercynian); and 3) SEDEX (Hercynian)-hydrothermal (Yanshanian) superimposing-type. Two generations of cassiterite (Cst-1 and Cst-2) were identified based on their microscopic features and CL images: Cst-1 is dark brown with distinct banded texture (euhedral-subhedral), whilst Cst-2 is light brown in color and cut Cst-1 (as veins) or distributed on the Cst-1 margin. They are both replaced by chlorite and quartz. The Huanggangliang cassiterite has relatively high Fe (median 4828 ppm) and W (median 273 ppm), but low Nb2O5 (<0.08 wt%) and Ta2O5 (<0.09 wt%) contents, distinct from SEDEX-type cassiterite but similar to granite-related cassiterite.Cst-1 has higher Fe-W-U contents than Cst-2, which reflects that Cst-1 was formed under relatively high temperature. Meanwhile, Cst-2 is relatively HFSEs-enriched, suggesting that the metallogenic environment had become more acidic. The cassiterite, zircon and garnet samples were U-Pb dated to be 137.10 +/- 3.65 Ma, 138.45 +/- 0.45 Ma, and 136.03 +/- 1.22 Ma, respectively. Considering the Huanggangliang geology, cassiterite geochemistry and published ages from Sn-polymetallic deposits in the southern Da Hinggan Range, we suggest that the regional Sn mineralization occurred mainly in 139-134 Ma, and that the Huanggangliang deposit is best classified as skarn-type, closely related to Yanshanian magmatic-hydrothermal activity.