Hydrothermal activity of the Hetaoqing iron-copper deposit in Wuding, Yunnan and its similarities and differences with the Yinachang iron-copper deposit

Just like the Yinachang iron-copper deposit, the Hetaoqing iron-copper deposit in the Wuding fault basin, Yunnan is interpreted to be the iron oxide copper-gold deposit in central Yunnan. Although the similarities appear in the two above-mentioned iron-copper deposits, there are additional differences in ore-forming element type and alteration type. The Hetaoqing iron-copper deposit occurs in the Luoxue Formation (Pt₂l), and abounds only in the element Fe and minor amount of the element Cu, without the enrichment of the element Au. The ore types are represented by the dense massive magnetite ores, and silicatization is considered to be the main alteration type associated with the mineralization. The imported elements SiO₂, Al₂O₃, MnO and Na₂O and the exported elements CaO, MgO, H₂O and CO₂ have disclosed that the silicatization may coexist with the decarbonatization in the Hetaoqing iron-copper deposit, while the sodiumization is nearly synchronous with the silicatization and decarbonatization, or slightly later than the silicatization. In the ore-bearing wall rocks, all the values of n(SiO₂)/n(Al₂O₃) > 3.6, n(Al)/n(Al + Fe + Mn) > 0.5, and n(Al₂O₃)/n(Al₂O₃ + Fe₂O₃)=0.12-0.36 have reflected that the Hetaoqing iron-copper deposit was formed in the extensional environments with the shallower sea water depths during the diagenetic processes.