Geological Characteristics And Geochemistry Of Phosphate Deposits In Baiyan Mining Area Of Wengfu Phosphate Mine In Guizhou Provinve

Wengfu Phosphate Mine is a large marine sedimentary phosphate rock deposit with large reserves,good quality and easy mining.It is composed of Baiyan mining area and Gaoping mining area.Since the discovery of Wengfu Phosphate Baiyan mining area,predecessors have made more achievements in the geological background,sedimentary characteristics,genesis and material source of Wengfu Phosphate Baiyan mining area.At present,the Chuanyandong ore section and Datang ore section under mining in Baiyan mining area have good quality and high grade.These two ore sections are selected for research.Through field geological investigation,optical microscope observation,inductively coupled plasma emission spectrum and mass spectrometry,scanning electron microscope and energy spectrometer,LA-ICP-MS and other experimental methods,the characteristics of major elements,trace elements,rare earth elements and in-situ element geochemistry of the two ore sections are compared and analyzed,The basic laws of geochemical characteristics of the two ore blocks are summarized,and the following understandings are obtained:(1)Through rock and mineral identification,electron optical microscope analysis,inductively coupled plasma emission spectroscopy and mass spectrometry,scanning electron microscope and energy spectrometer analysis,the main mineral components of phosphorite in Chuanyandong ore section and Datang ore section are basically similar,mainly fluoroapatite,and the secondary minerals are dolomite,quartz,pyrite,calcite,chalcedony,barite,hydromica,clay minerals and organic matter.Fluoroapatite is composed of amorphous collophanite,cryptocrystalline apatite and microcrystalline apatite,in which amorphous collophanite is the main body.The ore types include striped and banded sandy detritus phosphorite,dolomitic phosphorite,dense phosphorite,massive sandy detritus biological particle detritus phosphorite,black argillaceous phosphorite,as well as crystal cave,siliceous detritus phosphorite and other structures.(2)The P2O5 content of phosphorite in the Chuanyandong section and Datang section is high,which is higher than the national average grade of phosphorite.However,the difference lies in that the P2O5 content of ore beds a and b in the ore section through the Chuanyandong is relatively stable,and the P2O5 content of the upper part(ore bed a)is slightly lower than that of the lower part(ore bed a).The P2O5 value of each section of a seam in Datang ore block changes stably,while the P2O5 value of each section of b seam changes greatly.There is a positive correlation between P2O5 and CaO in the two ore blocks.Carbonate platform is the premise of phosphorus accumulation;There is a positive correlation between Ca/Ca+Fe value and P2O5 content.The marine environment with high salinity is more conducive to phosphorus deposition..(3)The contents of trace elements such as As,Ba,U,Sr,Mo,Be and Pb in phosphorite in Chuanyandong ore section and Datang ore section are high.By analyzing the characteristics of characteristic elements on U/Th,Co/Ni and V/(V+Ni),it is reflected that the phosphorite in the two ore blocks in the study area has the influence of hot water deposition in the deposition process.During the deposition process of phosphorite layer from the lower part(ore layer a)to the upper part(ore layer b),the sedimentary environment changes from anoxic to oxygen enriched.(4)The characteristics of rare earth elements in Chuanyandong ore section and Datang ore section are similar.Rare earth elements mainly occur in collophanite.Ore layer a in the early stage of phosphorus formation is deposited in anoxic reduction environment,and ore layer b in the late stage of phosphorus formation is deposited in relative oxidation environment,the negative abnormal value of δCe changes from ore bed a to ore bed b,and the scatter projection of ceanom value and nd content parameters also reflects that phosphate is formed in the transitional environment of reduction oxidation at a higher deposition rate,and the sedimentary environment of the upper b ore bed is more oxidizing than that of the lower a ore bed.The change of sedimentary environment is the main controlling factor for the formation of different types of phosphorite.(5)The in-situ element geochemical analysis of Chuanyandong ore section and Datang ore section shows that rare earth elements mainly occur in collophanite,and the in-situ analysis of phosphate rock of ∑REY is higher than that analyzed of ∑REY by ICP-MS.In a single phosphate rock particle ∑REY is uneven,from edge to center,the change of ∑REY content has a certain regularity.Near the edge of the same phosphorus ore particle the content of ∑REY is generally higher than that in the particle,the content of dolomite ∑REY is generally lower than that of collophanite.Among different ores,collophanite and arenaceous collophanite are relatively deficient in light rare earths,while medium and heavy rare earths are relatively enriched.Dolomite is in a deficit state except for individual heavy rare earths.