Research On Alteration Rocks And Mineralogical Characteristics Of Xiangyangping Uranium Deposits In Miao’ershan,Northern Guangxi

Miao’ershan uranium orefield is one of the five largest uranium orefields,but as the newly found deposit in Miao’ershan,the Xiangyangping uranium deposit hasn’t been studied completely.The study of aspects,like mineralogical characteristics of rocks,migration changes of elements before and after alteration and the metallogenic sources,plays a crucial role in understanding the cause of deposits and directing directions of prospecting.By comparing and studying the chemical components of biotite and chlorite in Xiangcaoping and Douzhashan granites on both sides of Xiangyangping uranium deposit,the author judges the affiliation of ore-bearing granite in Xiangyangping uranium deposit.On the basis of that,the author compares the main elements,trace elements and rare earth elements of granites before and after alteration in Xiangyangping uranium deposit,and studies the mineralogical characteristics of accessory mineral（zircon,monazite and xenotime）and uraninite minerals（uranothorites and uraninite）in altered granites.The findings are as follow.Both the Xiangcaoping and Douzhashan granites belong to typically peraluminous S-type granites in southern China and all chlorite is prochlorite formed in the low-temperature environment.Compared with the biotite and chlorite in Xiangcaoping granites,that of Douzhashan granites has richer the irons of F,Al,Fe²⁺,Ti,AlVI,Mg²⁺ and so on,Which illustrates that the degree of magmatic evolution,the reducing capacity,and uranium in its sources are higher in Douzhashan granites.All these features indicate that Douzhashan granites are more suitable for uranium mineralization than Xiangcaoping granites.Therefore,we believe that the granite in the Xiangyangping uranium deposit tends to be the Douzhishan rock mass.The uraninite found in altered granites of Xiangyangping uranium deposit further proves the status of uranium-bearing granites in this area.Compared with unaltered granites,altered granites present lower degree of Si,Na and Fe,higher degree of K,Mg,Ca,A/NK and A/CNK,and loss of ignition.What’s more,altered granites present richer Rb,Ba,Th,U and Ce,lack of Ta,Nb,Zr,Hf,Eu,Y,Yb,Lu and so on.They also have the characteristics of addition of LREE,loss of HREE,the difference degree between LREE and HREE and abnormal of lack Eu become more obvious.Minerals,like zircon,monazite and xenotime,of altered granites in Xiangyangping uranium deposit have native and secondary ones.After the hydrothermal fluid’ effect,native zircon and monazite can be altered into secondary minerals like xenotime and uranothorites.The content of U,Th,P and Y decreases in altered zircon.The content of U,Th,P and Y decreases in altered monazite,while the content of Fe increases.During the alteration of zircon and monazite,there are activation and transition in uranium of the accessory minerals that transfers from uranium-bearing accessory minerals to generate uranium minerals,so the content of active U increases.Under the later stage hydrothermal fluid’ effect,minerals,rich of U such as uranothorites and xenotime,can provide certain uranium sources for Xiangyangping uranium deposit.