Combined zircon and cassiterite U-Pb dating of the Piaotang granite-related tungsten-tin deposit, southern Jiangxi tungsten district, China

The large low-grade Piaotang W-Sn deposit in the southern Jiangxi tungsten district of the eastern Nanling Range, South China, is related to a hidden granite pluton of Jurassic age. The magmatic-hydrothermal system displays a zonation from an inner greisen zone to quartz veins and to peripheral veinlets/stringers (Five-floor zonation model). Most mineralization is in quartz veins with wolframite > cassiterite. The hidden granite pluton in underground exposures comprises three intrusive units, i.e. biotite granite, two-mica granite and muscovite granite. The latter unit is spatially associated with the W-Sn deposit. Combined LA-MC-ICP-MS U-Pb dating of igneous zircon and LA-ICP-MS U-Pb dating of hydrothermal cassiterite are used to constrain the timing of granitic magmatism and hydrothermal mineralization. Zircon from the three granite units has a weighted average Pb-206/U-238 age of 159.8 +/- 03 Ma (2 sigma, MSWD = 0.3). The cathodoluminescence (CL) textures indicate that some of the cassiterite crystals from the wolframite-cassiterite quartz vein system have growth zonations, i.e. zone I in the core and zone II in the rim. Dating on cassiterite (zone II) yields a weighted average Pb-206/U-238 age of 159.5 +/- 1.5 Ma (2 sigma, MSWD = 0.4), i.e. the magmatic and hydrothermal systems are synchronous. This confirms the classical model of granite-related tin-tungsten mineralization, and is against the view of a broader time gap of >6 Myr between granite magmatism and W-Sn mineralization which has been previously proposed for the southern Jiangxi tungsten district. The elevated trace element concentrations of Zr, U, Nb, Ta, W and Ti suggest that cassiterite (zone II) formed in a high-temperature quartz vein system related to the Piaotang granite pluton. (C) 2016 Elsevier B.V. All rights reserved.