Rock Features And Genesis Of Xiaoshan Uranium Deposit In Ganxiang Boundary

Lujing uranium orefield is located in the middle of Zhuguangshan complex rock mass and is one of the most important granite-type uranium orefields in South China.Cataclastic altered rock type uranium deposit is an important part of the ore field,Xiaoshan uranium deposit is a newly discovered cataclastic altered rock type uranium deposit located in the middle of Lujing ore field.In this paper,the Xiaoshan uranium deposit which in the Lujing uranium orefield was taken as the research object,using the modern analytical technology of ore deposit of typical rock（ore）stone samples fine lithology,mineralogy,main content,trace and rare earth elements geochemistry analysis,system analysis of the typical ore deposit rock characteristics,and combining previous research results to discusses the genesis of ore deposits.The main result are as follows:（1）Alkali-metasomatic alteration is developed in xiaoshan deposit,and the alteration zone has obvious zonation characteristics,The vertical mineralized alteration profile in borehole ZK3-8 is studied,the altered section is transformed from mineral-bearing alkali metasomatic rock in the center to alkali metasomatic granite on both sides and finally to fresh granite.The main alteration types are alkaline feldspathification,hydromica,chloritization and hematite.Alkali metasomatism superposition hematite and hydromica are beneficial to uranium mineralization.（2）The petrogeochemical analysis shows that the host rock is S type granite,it may be the product of partial melting of aluminum-rich metamorphic rocks in the upper crust under the condition of decompression and warming.The contents of Si O₂ in alkali-metasomatism granites and alkali-metasomatism mineralized rocks decrease gradually,and the contents of K₂O and Fe₂O₃ and Fe₂O₃/Fe O increase multifold,and the quartz content decreases obviously,corresponding to the development of alkali-metasomatism and hematite,The higher U and Pb contents and flatter HREE distribution curves indicate that alkali metasomatism not only creates a favorable physical and chemical environment for uranium unloading and precipitation in ore-forming fluids,but also may activation of uranium in biotite and accessory minerals in surrounding rocks.（3）Mineralogical studies show that:Uraninite,uranite-thorium,monazite,xenotime,zircon,apatite,rutile and other uranium-bearing accessory minerals are developed in alkali-metasomatic rocks of different degrees.Uraninite and uranite-thorium have high uranium content,unstable hydrothermal alteration conditions and easy uranium release.Uranium is easily released in the alteration of monazite to orthofluorocarbonite and xenotime to secondary apatite.Zircon is difficult to release uranium because of its stable structure.Apatite,rutile uranium content is low,poor uranium capacity.In conclusion,uraninite and uranite-thorium in granite are the main uranium source minerals,while monazite and xenotime are the secondary uranium source minerals.