Occurrence State And Enrichment Mechanism Of Dispersed Elements In Typical Lead-zinc Deposits Of Shaanxi

The content of dispersed element is very low in the earth’s crust (mostly10^-9)，widely dispersed in the rock，rarely appearing in the form of an independent mineral，mainly presented in lead and zinc deposits in the manner of isomorphism ormechanical mixing，playing an important role in the national economy. Lead-zincmine in Shaanxi Province is rich， associated dispersed elements with greatereconomic value. Making Fengtai ore cluster region Qiandongshan ore deposit，Zhenxun ore cluster region Huangshiban ore deposit，Yangtze margin Mayuan oredeposit as typical lead-zinc deposits，the thesis studys the regional geologicalbackground，geological characteristics，ore geochemical characteristics and otheraspects of deposit characteristics， analysising the occurrence and enrichmentregularity of dispersed elements in the deposit.The results of eological survey and mineral petrography，geochemistry，isotopegeochemistry shows：Qiandongshan lead and zinc deposit located in the southwest ofFengtai ore cluster region，occurs in the chert of the top of Gudaoling group. Theorebody is bedded，lenticular. The main ore minerals are sphalerite，galena and pyrite.Ore structure mainly are strawberry-like texture，account texture，skeletal texture，and banded，disseminated and massive structure. The Fe2O3/FeO ratio of rocks andores were less than1. Eu also shows a low negative anomalies，which shows ore wasformed in a relatively reductive environment. The high content of W，Sn in ore showsthe deposit was influenced by hydrothermal activities. Combined with S isotope，Pbisotopic compositions，we regard the deposit as an SEDEX-type lead-zinc deposit.Mayuan lead-zinc deposit located in beiba uplift monument in the southeast edge ofthe Yangtze platform margin. The deposit is located in dolomitic breccia of DengyingFormation，controlled by stratum and structure control. The main ore minerals aresphalerite， galena and pyrite. Ore texture mainly are hypidiomorphic andxenomorphic granular textures and ore structure mainly are brecciated，banded，stockwork structure. Ore enrich Cs、Ba、Sr、Tl and other high field-strength elements.The REE curve of Sphalerite is Eu positive anomalies，which shows deposit wasformed in an oxidizing environment. S isotopic composition indicate that S came from the Sinian seawater sulfate，and Pb isotope composition indicate that Pb came frommantle mixed source characteristics，so we consider the deposit belongs to MVT-typePb-Zn deposit. Huangshiban lead-zinc deposit located in the south of Zhenxun orecluster region. Orebody located in the sericite quartz schist of the Lower SilurianMeiziya Formation. Orebody is layerd and lenticular. The main ore minerals aresphalerite，galena and pyrite. Ore structure mainly are strawberry-like structure，account structure，and lamellar，banded，brecciated structure，so we consider thedeposit belongs to SEDEX-type Pb-Zn deposit.By electron microprobe analysis and surface scanning，elements correlationanalysis，R-cluster analysis，dispersed elements of Qiandongshan，Mayuan andHuangshiban lead and zinc deposit are mainly in the form of isomorphism in primarysulfide minerals. Cd substituted Fe into the main sphalerite lattice. Ge，Ga mainlyoccurs in galena crystal lattice. In content are basically below the detection. Thedispersed elements in main mineral also have instructions for significance. Thecontent of Cd in Mayuan sphalerite is higher，an average of4594×10^-6，showing thecharacteristics of MVT-type lead-zinc deposits. The content of Cd in Qiandongshanand Huangshiban sphalerite is lower，an average of2092×10^-6、2473×10^-6，showingthe characteristics of SEDEX-type lead-zinc deposits. The content of Cd in MVT-typelead-zinc deposits is double of SEDEX-type lead-zinc deposits. The content of Ce insphalerite of the three deposits is greater than100×10^-6，suggesting that thetransformation of sedimentary origin. The content of Zn/Cd in sphalerite of the threedeposits is less than500，showing metallogenic temperature is low.By analysisng the content of dispersed elements of ore，concentrate，tailings inQiandongshan，Mayuan and Huangshiban lead and zinc deposit，the content of Cd inconcentrate of Qiandongshan and Mayuan lead and zinc deposit，the content of Cd，In in concentrate，the content of Ge in tailings of Huangshiban lead and zinc depositall have bigger uses. If dispersed elements are used in deposits, they will creategreater economic benefits.