新疆阿尔金东段塔什达坂花岗岩、伟晶岩年代学及地质意义OA

Tashidaban lithium deposit is one of the important lithium deposits discovered by our team in the eastern section of Altyn rare metal metallogenic belt in recent years.Through field geologica1 investigation,U-Pb dating of zircon and columbite,zircon Hf isotopes and comprehensive study of petrogeochemistry,this paper discusses the diagenetic and metallogenic epoch and regional magma-hydrothermal activity.Some conclusions have been reached:Tashidaban lithium deposit is located in the eastern part of the Altyn orogenic belt,the orebody exists in the granite pegmatite,the surrounding rock is mainly the Bashikorgan Group of the Changcheng system and the Taxidaban Group of the Jixian system,and the granites of different grain sizes are developed in the around.The zircon U-Pb age of the fine biotite monzonite granite in the west of Tashidashan lithium Mine is(477.8±2.5)Ma,the zircon 176Hf/177Hf values are 0.282 319～0.282 405,the εHf(t)values are-5.5～-2.5,and the two-stage model age(TDM2)is 1602～1793 Ma.Combined with the geochemical characteristics of rocks,it is believed that the source rocks are paleo-proterozoic sedimentary materials.The U-Pb age of the zircon from Tashidaban containing black turmaline pegmatite is(423.1±2.3)Ma,which represents the formation age of pegmatite.The 206Pb/238U ages of spodumene pegmatite-bearing niobium-tantalite are concentrated in 400～422 Ma and 343.3～370.7 Ma,reflecting the characteristics of multi-stage hydrothermal activities.Which shows that the diagenetic age of the Tashidaban pegmatite is obviously inconsistent with that of the monzonite granite on the west side of Tashidaban,indicating that the fine biotite monzonite granite on the west side of Tashidaban is not the direct parent rock of the pegmatite.