Genetic Study And Metallogenic Prediction Of The Liufengshan-Shuicun Lead-Zinc Deposit In The West Of Dayaoshan,Guangxi

The Liufengshan Pb-Zn deposit and the Shuicun Pb-Zn-Cu deposit located in the middle part of the western Dayaoshan polymetallic ore concentration area.There are many mineralization points in this area.The predecessors mainly prospected in terms of lithology,fault structure and ore bodies have been mined,and the prospecting work didn't make a big breakthrough over the years.On the basis of summarizing the geological characteristics of the regional and typical deposits,this paper focuses on the analysis of trace elements in the surrounding rock and gangue minerals,REE in calcite,electron probes in ore,S-Pb isotope analysis and microscopic temperature measurement of fluid inclusions.Then we explored the metallogenic mechanism and genesis of the deposit in this area,and combined geophysical exploration to predict mineralization.Mainly achieved the following conclusions and understanding:(1)The ore body of the Liufengshan-shuicun Pb-Zn deposit often cut through strata,the top and bottom surrounding rock of the bedding strata ore body are altered,and the mineral crystal grains are thick.Also,the mineralization and indicator elements Cu?Pb?Zn?Ag?Sb and As are obviously enriched near the ore-controlling fracture,and are significantly reduced away from the fracture,showing epigenetic mineralization characteristics.(2)?REE of the Liufengshan ore-bearing calcite is 1.45×10-6?30.10×10-6.LREE enriches and HREE is depleted,the distribution curve is right-dip.The?Ce is weakly negative,and the 8Eu is negatively abnormal,which indicating the metallogenic environment of low-temperature and oxidation.Fluid inclusion characteristics show that the ore-forming fluid is medium-low temperature(98.3?254.2?)and medium-low salinity(0.18%?13.62%).And the uniform temperature-salinity chart show isothermal mixing characteristics,its formation is likely to experience the mix of high salinity basin brine and low salinity atmospheric precipitation.(3)The S isotope of the Shuicun Pb-Zn-Cu deposit shows that pyrite?sphalerite and galena are characterized by sulfate-reducing sulfur,and chalcopyrite is characterized by deep-source sulfur;Pb isotope shows that Pb is mainly derived from the upper crust;The sphalerite is enriched in Cu?Ag?As?Ge?Cd?Sb and the values of Ga/In?Zn/Fe?Ga/Ge indicate that the ore-forming temperature is medium-low temperature.The Fe-Cd?Fe-As diagram of sphalerite and Fe/S ratio of pyrite show characteristics of the MVT type Pb-Zn deposit.(4)Comprehensive comparison shows that the Liufengshan Pb-Zn deposit and the Shuicun Pb-Zn-Cu deposit are similar to the typical MVT type Pb-Zn deposit in terms of geological characteristics and elemental geochemical characteristics.Therefore,the two deposits are identified as MVT deposit.(5)It is proposed by geological survey that two interfaces in this area are favorable mineralization areas.Namely the Devonian Shanglun Formation dolomite and the underlying Yujiang Formation siltstone Si/Ca interface(large interface).And the Devonian Shanglun Formation dolomite and the Ertan Formation limestone Ca/Mg interface(small interface).Combined with ore-controlling faults and geophysical anomalies,we located three favorable ore-forming target region,and found dolomitization?baratization?sericitization and Pb-Zn mineralized zone with thickness over 60m in Si/Ca interface of the target region,which shows that the interface is another favorable metallogenic site in this area.Through this research,it is pointed out that Si/Ca interface between Yujiang Formation and Shanglun Formation is another important ore-storing space in this area,besides traditional prospecting direction of lithology and tectonic.