Ore-bearing Potentian And Matallogenic Regularity About Rare Metal Of Fengchuiluodai Granite In The Changchengling,Hunan

In recent years,the Changchengling rubidium deposit is a super-large rubidium deposit newly discovered in the overlapping part area between the Nanling nonferrous metals metallogenic belt and Qinghang nonferrous metals metallogenic belt in Yizhang County,southern Hunan province.Rubidium ore bodies are located in NE,NW,and SN fault structures in the Changchengling area.The paper selects the Fengchuluodai rock mass as the research object.Based on the field fine structural alteration lithofacies mapping and systematic sampling work,indoor petrography,micro mineralogy,experiments of major trace elements and trace elements and rare earth element of rocks,major rock-forming minerals LA-ICPMS in-situ micro-analysis,the paper carrys out a series of studies about rock geochemical characteristics,the ore-bearing properties of rare metals,the characteristics of mineral chemical composition,the degree of magma evolution,the law of rare metal enrichment,and the metallogenic mechanism of rubidium deposits.The main conclusions are as follows:（1）The test results of the main trace elements and rare earth elements experiment show that the Fengchuluodai granite porphyry rich in Si,alkali,Al,and the granite porphyry belongs to aluminum high potassium calc-alkaline rock.Trace elements are rich in large ion lithophile elements like K,Rb,U,Th,and depleted in high field strength elements,such as Ba,Sr,Ti.The total amount of rare earth elements is extremely low.The differentiation is intense,and the light rare earths are enriched.TheδEu is especially deficiency.The distribution pattern has a"seagull"quartet effect,indicating that the magma has undergoned a high degree of evolution.（2）By counting the content of rare metals in the granite porphyry and cryptoexplosive breccia of the Fengchuanluo belt rock mass,the results show that the content of Rb is 1525×10^-6and conforms the industrial grade,and the content of Nb+Ta is 140×10^-6and conforms the boundary grade.The rubidium mineralization of the Fengchuluo belt rock mass is relatively uniform and has good prospecting potential.（3）Through the LA-ICPMS in-situ microanalysis of the main rock-forming minerals,the results show that muscovite has the most enriched Rb content in the Fengchuluo belt,and feldspar has the second Rb content.Muscovite can be divided into primary and secondary points.The primary muscovite is evenly distributed in the granite porphyry,which is a typical muscovite precipitated by the condensation and crystallization of magma.The secondary muscovite mainly exists in the granite porphyry breccia,mostly along the small cracks of the breccia matrix,and the formation is related to the fluid that initiates the cryptoexplosion.The type of native muscovite is muscovite-polysilicon muscovite,and the secondary muscovite is lithium-polysilicon muscovite.The geochemical characteristics of native muscovite indicate that magma has undergone a high degree of differential evolution.（4）There are obvious differences in the enrichment of different rare metals in native muscovite and secondary muscovite.The content of Nb,Ga,and Sn rich in native muscovite and the Li,Rb and Cs rich in secondary muscovite.The phenomenon shows Nb,Ga,and Sn mainly converge in the magma melt stage,and The Li,Rb and Cs in secondary muscovite are more enrich than these in native muscovite,and the phenomenon reflects Li、Rb、Cs may be further enriched in the fluid that precipitated at the late stage of magma.（5）Based on the above research about the ore-bearing properties of rare metals,the characteristics of mineral chemical composition,the degree of magma evolution and the law of rare metal enrichment,the mineralization of rare metals in the Changchengling mining area is closely related to the highly differentiated evolution of magma and the accompanying magmatic hydrothermal action.