The Mineralization Characteristics Of Jiajika Granite Pegmatite Rare Metal Deposit

Jiajika granite pegmatite rare metal deposit is located in the middle of the Songpan-Ganzi orogenic belt,western Sichuan.It is one of the largest rare metal deposits in China and even in Asia,with a complete Li-Be-Nb-Ta mineralization series.In this paper,based on the previous research results,through the comprehensive analysis and research of the granite,pegmatite and pegmatite-type rare metal deposit in the research area,the following understandings are obtained:?1?Jiajika granite is the ore-forming parent rock of the pegmatite-type rare metal deposit,which provides a material source for the formation of the deposit.There are three main pieces of evidence:?1?Granite and pegmatite belong to the same S-type granite,both of which are characterized by high silicon,alkali-rich,and trans-aluminous,and the light and heavy rare earth fractionation is obvious.The Eu negative anomaly is obvious,and the rare earth complex map shows the characteristics of homologous gradation.?2?t The methyl card granite body is mainly composed of two-mica granites,and has high content of rare metal elements such as Li,Be,Nb and Ta.The pegmatite invade into the two-mica granite body and it's internal and external contact zones,which has the characteristics of multiple stages of mineralization.?3?The Pb-Sr-Sm-Nd-Li isotope signature indicates that the granite has the same source as the pegmatite ore-forming material.?2?The mineralized fluid of the rare metal deposit is derived from high temperature and high pressure hydrothermal fluid after the magma period.The mineralized fluid of the rare metal deposit is derived from high temperature and high pressure hydrothermal fluid after the magma period.The mineralization temperature is mainly between high to medium temperature?about 350?to 250??,the fluid pressure is between 492×10⁵Pa to 320×10⁵Pa,and the salinity is mainly between 5.7 to 10.8.The liquid phase components of the fluid inclusions are mainly Li⁺?K⁺?Na⁺?F^-?Cl^-?SO₄^2-,and the gas phase components are mainly H₂O and CO₂.?3?The LA-ICP-MS zircon U-Pb dating of the rock mass indicates that the age of the granite body is 220±2.3 Ma.Combined with previous data from predecessors,the pegmatite veins are formed around 210 Ma.The deposit was formed at the end of the Indosinian movement-early in the Yanshan movement.?4?Through the study of granite rocks and pegmatites,this paper systematically summarizes the metallogenic characteristics of the granitic pegmatite-type rare metal deposits,and has important guiding significance for the study of the some deposits in the Songpan-Ganzi orogenic belt.