Geological And Geochemical Characteristics Of The Pb–Zn–Cu VMS Deposit Within The Changning-Menglian Suture Zone, Yunnan Province, SW China

Chang Ning-Meng Lian suture zone is located in Sanjiang tectonic belt, the southern tip of the region. It is one of the important metallogenic belt of Sanjiang.It has passed through the ancient tethys ocean basin opening and expansion, the marginal ocean basin subduction, ocean basin closure, and collision orogenic process, controlled by the formation and evolution of the Tethys Ocean, Changning-Menglian suture zone evolved a series of unique VMS-type deposits, like Tongchang Ji–LaochangVMS-type Ore concentration area.Tongchangjie Ore concentration area is produced in Carboniferous-Permian ophiolite of Tongchangjie,the ore body is lie in basic volcanic series. The Laochang Pb-Zn Ore concentration area locate in Carboniferous-Permian volcanic rocks-combination of Marine carbonate sequences, Often appear withmiddle ocean ridge basalt, Cu-Pb-Zn orebody is locate inthe early carboniferous-late carboniferous basic volcanic series. Mineralization zoningof the two concentration area is clear, have shown "black-yellow(galena-sphalerite) under(pyrite-chalcopyrite)" zoning properties.The ore-forming fluid environment of Tongchangjie is in the low, medium low salinity, density fluid; The ore-forming fluid of Laochang have a high temperature, high salinity,lowdensity and CO2 riched fluid environment;S isotope analysis showed that the sulfide ore δ34S values of Tongchangjie range between-0.76‰~3.79‰, the whole value was close to zero, and has a significant distribution tower, sulfur isotopic composition is similar to the mantlesulfur;the sulfide oreδ34Svalues of Laochang between around zero, indicating the sulfur mainly comes from direct differentiation shallow magma chamber.Whole-rock geochemistry results showed that the ore volcanic rocks of Tongchangjie are mainly sodic, potassium tholeiitic basalts, the ore volcanic rocks of Lachang are mainly high-K quality, sub-alkaline tholeiitic basalts.Basalt trace REE pattern of Tongchangjieis almost parallel with the N-MORB basalts, indicating its structural environment is middle ocean ridge(MORB); basalts of Laochang trace elements composition is similar to oceanic island basalts(OIB), it indicates that the metallogenic environment is oceanic island environments.So, it can concluded that Tongchangjie and Laochang VMS-type Ore concentration areawere produced at different stages of Changning-Menglian Tethys oceanic crust expansion environment,producedCyprus-type deposits of middle ocean ridgeenvironments and Besshi-type deposits of oceanic island environments.