Characteristics Of Ore Geology And Ore-forming Fluids Of The Shangdaohui Mo Deposit In Xiong’ershan Region

The Shangdaohui Mo deposit is located in the Xiong’ershan-Waifangshan region which is in the western region of Henan Province, China. The orebodies,controlled by the secondary fault of the Machaoying fault, occur as veins and are hosted by Mesoproterozoic intermediate to felsic volcanic rocks of the Xiong’er Group. The metallic minerals are molybdenite and pyrite. The silicification,K-felsparization and carbonatization are the main hydrothermal alteration types.The hydrothermal ore forming process can be divided into three stages, quartz+ pyrite stage（early stage）, quartz + molybdenite + polymetallic sulfide stage（middle stage） and quartz + calcite stage（late stage）. Three types of fluid inclusions can be identified in the Shangdaohui Mo deposit, including W-type（aqueous）, C-type（CO₂-rich）, S-type（daughter mineral-bearing）. The early stage quartz contains mostly W-type, C-type and minor S-type fluid inclusions, the middle stage quartz contains C-type, W-type and S-type fluid inclusions, and the late stage calcite only contains the W-type fluid inclusions. The homogenization temperature of early-stage fluid inclusions ranges from 210°C to 390°C, with salinity of 1.0%-13.4% and27.2%-33.2%. The middle-stage homogenization temperature is 180°C-300°C, with salinity of 0.3%-14.1% and 27.3%-28.5%, and the last-stage homogenization temperature ranges 120°C-220°C, with salinity 0.1%-14.2%. The ore-forming fluid evolved from carbonic to aqueous from early to late mineralization stage. Fluid boiling occurred in both early and middle stages, and resulted in release of CO₂,which caused the precipitation of the Mo S2 and other sulfides. Trapping pressures estimated according to the C-type fluid inclusions are 148-371 MPa and 108-383 MPa in the early and middle stages, corresponding to metallogenic depth of 5-14 km.The results of Hydrogen, Oxygen, Carbon, Sulfur stable isotope show that theδ¹⁸O of quartz ranges 9.7 ‰ to 14.1 ‰, the δ¹⁸OH₂O in the range of 0.38‰- 5.14 ‰.The dD of the fluid ranges-83 ‰ to-73 ‰. H-O isotopic composition of the fluid inclusion in quartz indicates that the water meanly from metamorphic water（magmatic water） and rain water. C-O isotopes show that the δ13CPDB ranges-6.3 ‰ to-11.8 ‰, average of-8.2 ‰. C-O isotope figure shows from granite to the trend of Marine carbonate. It showed that C-O isotope source may come from the magmatichydrothermal or Guandaokou group and Luanchuan group, at the same time may join the atmospheric precipitation. Pyrite δ34S ranges-8 ‰ to-6 ‰（except-14.7 ‰）, and it is 1 ‰ to 3 ‰, 4 ‰- 6 ‰ in the Xiong’ershan group and Taihua group.It is easy to find that the formation of the Shangdaohui Mo deposit belongs to Mesozoic. It belongs to the typical orogenic metallogenic stage. Combined with regional data, the Shangdaohui Mo deposit formed in the collision of post-orogenic extensional tectonic of the Qinling orogenic belt in Mesozoic. we have researched the regional geology, geological characteristics, fluid inclusions and stable isotope.Considering the tectonic evolution of the Shangdaohui Mo deposit, we suggest the deposit was formed in continental collision regime and the CMF model can be used to interpret its origin.