Detailed Determination Of The Mineralization Process Of The Tianzhu Barite Deposit In Guizho

During the Ediacaran-Cambrian transition period,many super-large and large barite（Witherite）minerals were developed on the edge of the Yangtze block in South China,but the material source and metallogenic model of barite are still controversial.In this paper,the Tianzhu barite deposit in Guizhou Province is taken as the research object,and systematic petrology and mineralogy studies are carried out.Trace element geochemistry and C,O,S isotopes are studied.The comparison method is used to finely determine the metallogenic process of the Tianzhu barite deposit from micro to macro,analyze and summarize the metallogenic regularity and metallogenic model,and establish the formation mechanism and metallogenic model of the Tianzhu barite deposit.Through the analysis and study of barite petrology and mineralogy,it is found that barite,dolomite,calcite and pyrite coexist.Locally visible witherite,hyalophane and other minerals.The barite is a porous structure with nodular,radial and rose-like growth,and the coarse-grained barite and microcrystalline barite are interbedded.In the sedimentary sequence,the metallogenic process is mainly composed of three metallogenic stages.Each metallogenic stage forms different mineral assemblage characteristics,forming the mineral assemblage distribution characteristics of submarine cold spring jet deposition.In the study of element geochemistry,barite ore-bearing rock series are rich in V,Ni,Mo,Cu,Zn and other elements,with a large range of rare earth elements,light rare earth specific gravity rare earth enrichment,δCe negative anomaly,δEu positive anomaly.The geochemical characteristics of heavy elements indicate that the sedimentary environment of barite is anoxic and reducing environment.The source of ore-forming materials is mainly formed by the degradation and fractionation of organic matter in the underlying strata and the microbial action of marine sulfate reduction.Theδ³⁴S_Brtvalue of barite is slightly larger than that of seawater in the same period.Theδ³⁴S_Pyvalue of pyrite,δ¹³C andδ¹⁸O values of carbonate rocks are slightly lower than those of seawater in the same period,and there are differences in spatial distribution.Based on the isotope ratio and fractionation characteristics,it is considered that the metallogenic process of barite is consistent with the genesis of submarine cold spring jet,and different isotope fractionation characteristics are formed in each metallogenic stage.It indicates that sulfate is mainly derived from seawater and is controlled by organic matter oxidation and sulfate bacterial reduction.The rock mineralogy,element geochemistry and isotope distribution of the two ore concentration areas are compared and analyzed.It is considered that the cold spring jet center of barite is located near the Dahebian ore concentration area.Due to the factors such as source supply,sedimentary environment and seawater sulfate reduction fractionation rate,there are significant differences in the metallogenic stages of the two ore concentration areas.The structure of barite ore body,mineral assemblage relationship,ore body thickness and element geochemical characteristics are unevenly distributed.In the determination of the metallogenic process,it is considered that the Tianzhu barite deposit presents a multi-stage metallogenic process as a whole,that is,in the early metallogenic stage,the cold spring jet formed on the seabed is ejected from the seabed in the form of cold spring jet,which is mixed with the sulfate-rich reducing water body for enrichment and mineralization;in the late metallogenic stage,the concentration of fluid rich in barium and methane gradually weakened,forming an uninterrupted metallogenic process dominated by seawater deposition.