Petrogenesis Of Granites In The Shimensi Tungsten Ore District Of Northwestern Jiangxi Province And Implications For Tungsten Deposits

The Late Mesozoic Dahutang tungsten deposit, as one of the largest tungsten deposits in the world, is located in the eastern part of the Neoproterozoic Jiangnan Orogen. In this study, we investigated the petrography, mineralogy, zircon and cassiterite U-Pb geochronology and trace element concentrations of the Neoproterozoic and Yanshannian granitic intrusions in the Shimenshi ore district. Zircon U-Pb dating results of the Neoproterozoic biotite granodiorites and Yanshannian biotite granite porphyry, greisenized fine-grained granites and greisenized biotite granite porphyry are 829.9±4.7 Ma,145.5±3.6 Ma,152.6±2.0 Ma and 154.2±1.7 Ma, respectively. In particular, the crystallization ages of the Yanshannian granites are consistent with our new cassiterite U-Pb age results. The cassiterite mineral in the ore-related fine-grained biotite granites, contain higher tungsten concentration than those of other Yanshannian intrusions. This implies a higher tungsten concentration in the fine-grained biotite granitic magmas. Apparent temperatures for zircon crystallization calculated by Ti-in-zircon thermometer suggest lower temperatures of Yanshannian magmas with weighted average temperature ranging from 734℃ to 788℃. Trace element concentrations of zircon exhibit that fine-grained biotite granites forms in low oxygen fugacity conditions, which is potential for tungsten ores.