Characteristics And Genesis Of The Chengmenshan Copper And Molybdenum Deposit In Jiujiang, Jiangxi Province

The Jiurui ore concentrated district is an important part of the Middle and Lower Yangtze River metallogenic belt. The Chengmenshan Cu-Mo deposit is a representative multiple deposit in the district, with porphyry, skarn and massive sulfide orebodies. It is significant to study this deposit owing to its larger scale and unique geological characteristics. Detailed field investigation and indoor synthetic analysis have been carried out on the deposit, and its geological and geochemical characteristics ascertained in this thesis, with a focus on the discussion of the genesis of the Chengmenshan deposit, especially the massive sulfide orebody in them.The Chengmenshan Cu-Mo deposit is composed of three types of orebodies, namely porphyry Cu-Mo orebody, skarn Cu orebody and massive sulfide Cu orebody. There are some obvious differences in major ore mineral, ore texture and ore structure among these orebodies. The major ore mineral includes pyrite, chalcopyrite and molybdenite with a little magnetite and chalcocite in the porphyry Cu-Mo orebody, pyrite and chalcopyrite with a little sphalerite, panabase, bornite and digenite in the skarn Cu orebody, and lamellate pyrite and chalcopyrite in the massive sulfide Cu orebody. The ore texture is predominated by leaf-shaped and corroded-like textures in the porphyry Cu-Mo orebody, by relic and droplet-like textures in the skarn Cu orebody, and by colloidal and coble creep deformation in the massive sulfide Cu orebody. Correspondingly, the ore structure changes from disseminated and veinlet disseminated structures in the porphyry Cu-Mo orebody through lumpy and banded structures in the skarn Cu orebody to brecciated and laminar structures in the massive sulfide Cu orebody.The orebody associations and ore mineral assemblages combined;with isotopic analyses for ore minerals of the deposit indicate an overprinting origin of the Chengmenshan Cu-Mo deposit through two stages of hydrothmal mineralization. The obtained data support formation of the massive sulfide Cu orebody in the deposit not by contemporaneous sedimentation but by magmatic hydrothermal process.