Applications of Li isotopes in the study of granitic pegmatite-hosted rare metal deposits:A case study from the Songpan-Ganze-West Kunlun granitic pegmatite-type rare metal metallogenic belt
The Li isotope method,as a new and nontraditional isotope method,can provide important information to understand the origin and genesis of granitic pegmatite-type Li deposits.Based on previous works,we collect and summarize Li isotope data of granites,pegmatites,and corresponding metasedimentary rocks from typical rare metal deposits in the Songpan-Ganze-West Kunlun metallogenic belt.Based on the similar δ7 Li values between granites and metasedimentary rocks,we propose that the primary granitic magma originated from partial melting of metasediments at deep crustal levels.Notably,the δ7 Li values of parts of the granites are higher than those of the metasediments,which indicate that devolatilization fluids from the lower crust may be involved during crust partial melting.The Li isotopes of the pegmatites are consistent with those of the granites,suggesting that the pegmatites have genetic affinities with granitic magma.Both equilibrium fractionation and diffusional fractionation control the Li isotope fractionation of pegmatite,during which processes such as fluid exsolution and the separation of H2O-rich pegmatitic melt/fluids take place.This complex fractionation mechanism leads to the varied δ7 Li values from Li-poor to Li-rich pegmatite.Although there are some challenges for applications of the Li isotope method to granitic pegmatite deposits,it is believed that the Li isotope method has the potential to enhance rare metal metallogenic theory and mine exploration,and may be an important geochemical method in future research.
Li isotopesgranitepegmatiterare metalSongpan-Ganze-West Kunlun
国家科技期刊平台
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