In situ LA-MC-ICP-MS and ID-TIMS U-Pb geochronology of cassiterite in the giant Furong tin deposit, Hunan Province, South China: New constraints on the timing of tin-polymetallic mineralization

摘要

The Furong deposit, located in southern Hunan Province, China, is a newly-discovered giant tin deposit spatially associated with the A-type Qitianling granite. The petrogenetic link between the giant Furong tin deposit and the Qitianling granite batholith remains controversial because of the lack of precise dating for the tin-polymetallic mineralization. Here we report for the first time in-situ U-Pb data on cassiterite obtained by LA-MC-ICP-MS and the results are compared to ID-TIMS data. The in-situ LA-MC-ICP-MS analyses of the cassiterites provide a reliable age constraint for tin-polymetallic mineralization in the Furong deposit, yielding an isochron age of 159.9± 1.9 Ma (at 95% confidence level, MSWD = 18), which is indistinguishable from the ID-TIMS ~(206)Pb/~(238)U weighted mean age of 158.2 ± 0.4 Ma. The in situ U-Pb ages corroborate the Ar-Ar dates published for the Furong tin deposit, which indicate that the mineralization is coeval with the emplacement of the Qitianling granite batholith. These results provide further evidence of a close temporal link between the pluton's emplacement and tin mineralization in the Furong area. The data obtained clearly demonstrate that in-situ LA-MC-ICP-MS U-Pb dating of cassiterite is a robust geochronometer for direct dating of tin-polymetallic mineralization.