Geochemistry Character Of Xiongcun Copper-gold Deposit, Xietongmen County, Tibet

Xiongcun copper-gold deposit locat at sorth of Gangdishi ore belt within Xietongmen county, Tibet. Xiongcun porphyry deposit is a new super-size copper and gold deposit. Copper-gold are forming within quartz eyes bearing hornblend-quartz diorite porphyry and nearby tuff. Ore-forming body is un-regular branch, and whole body mineralized. The main alteration within intrusions are strong K-silicate and silicification. Silicification, andalusite, biotite, muscovite, and pyrite-sericite-quartz alteration are present within nearby wallrock. Alterated wallrock are volcanic tuff.Base on the study of total 41 elements analysis data of 172 boreholes and elements distribution on north-sorth, east-west cross section, the informations indicate that:The main element are Cu, Au, Ag, Pb, Zn, and related with each other. Cu and Au are forming within chalcopyrite. Two process result in ore-forming: most of Cu, Au, and Ag were formed at the first stage. The later stage result in forming Pb, Zn, Au, Ag, Cu.Cu, Au, Ag, Bi, Sb, Fe were bring-in on the ore-forming stage. Mg, Al, Mn, Mo, Ca, Na, Ba were take out at same stage. The distribution character of elements on the plane and cross section indicate that: from center to outside, the elements separated into several belt: Cu, Au, Ag, Bi, Sb, Fe→K, Mo, Ni→Mn, Pb, Zn, Ca, Na, W, Ba, (Fe).The orebody were partly destroyed by F1 and F1 formed on the after-oreforming, denudation on the surface, and biotite granodiorite formed on Jurassic.Xiongcun tuff and porphyry are calci to calci-alkaline, approximate to tholeiite, and forming in the arc island based on the geochemistry study.The result of isotope are showing that: 206Pb/204Pb: 18.16160～18.25980, 207Pb/204Pb: 15.53840～15.56800,208Pb/204Pb: 38.12680～38.30720, showing Pb coming from both mantle and crust.δD(‰): -83.597~-92.464,δ18O: -2.4~-0.89, indicate thermal water coming from magma and rainfall.The study of geochemistry, geo-character of orebody indicate that Xiongcun copper-gold were formed on the downthrust stage between India plate and Eurasia plate. Relic-ocean crust re-melt and move to upside, mixed with up-part crush, and final inrush to the tuff. The ore-body was reconstructed by later geological process.