Geochemical Characteristics And Genesis Of The Huize Yinchang Lead-zinc Deposit, Yunnan

Yinchang lead-zinc deposit is located in northeastern Yunnan,which is a Ge-Ag enriched lead-zinc polymetallic deposit concentrated district.The geotectonic position belongs to the transition zone of Xikang Yunnan axis of the southwestern margin of the Yangtze paraplatform and the southern part of platform fold belt in northeastern Yunnan.The ore-bearing strata of Yinchang lead-zinc deposit are dolomite strata in the upper part of Dengying Formation,which is a typical deposit hosted by carbonate strata of the Dengying Formation.Based on the regional geology and the geological characteristics of the deposit,this paper focus on the study of the geochemistry of Yinchang lead-zinc deposit,and ?34S of pyrite,sphalerite,galena,barite,and fluid inclusions in quartz.And discussed the sources of ore-forming fluid and ore-forming materials,as well as the genesiss of the deposit.The main achievements of this paper are as follows:1.The content of SiO2 in ore is between 23.61%and 49.55%,but the contents of Na2O?K2O and Al2O3 are relatively low.The content of ?REE range from 17.31×10-6 to 73.94×10-6(average of 35.54×10-6),LREE/HREE is between 1.89 and 3.84(average of 2.69),LaN/YbN is between 1.21 and 5.36(average of 2.9).It shows a relatively gentle right-leaning REE distribution pattern.The ?Ce are between 0.7 and 1.38(average of 0.95),most of which are more than 1.It shows a weak positive anomaly.The ?Eu are between 0.92 and 0.19(average of 1.05).It shows no obvious abnormality.2.?34S of galena and sphalerite were concentrated in 8.4‰?13.2‰(average of +10.5‰)and 10.8‰?13‰(average of +19.1‰),which were close to the range of seawater sulfur.Therefore,the sulfur might be mainly derived from seawater sulfate,which may be affected by mantle derived sulfur.?34S of barite change from +26.8‰ to +29.3‰(the range value is only 1.5‰),which indicate that the sulfur source is relatively single,and should be derived from the sulfate formation of lower Cambrian.?34S of pyrite change from-3.3?+1.5‰ and +4.6?+10.60‰(average of +1.3‰),which are wide range and within range of mantle derived sulfur.It is shown that the source of sulfur is not only the addition of mantle derived sulfur,but also with the participation of sulfur in seawater sulfate.3.The type of fluid inclusions in the quartz is rich in liquid phase.The average temperature is 178? to 240?,and the salinity is from 7.86wt%NaCleq to 12.84wt%NaCleq,and the density is from 0.89g/cm3 to 0.97g/cm3,and the metallogenic pressure is from 119.29 Mpa to 160.92Mpa,and the mineralization depth is between 1.3km and 1.8km.It shows that the fluid in the inclusion is medium low temperature,medium low salinity and low density fluid.4.The source of ore-forming materials of Yinchang lead-zinc deposit with the characteristics of multi-source.The dolomite of Dengying Formation is the main source of ore-forming material,and which is affected by magmatic rocks.So we summrize its metallogenic model for the"sedimentation-transformation" genesis.