Early Mineralization Age of the Hengjian Uranium Deposit: Constraints from Zircon SIMS U‐Pb Dating

The Hengjian uranium deposit is a typical hydrothermal deposit in the Xiangshan uranium ore field. The uranium mineralization ages of the Xiangshan deposits are poorly constrained, and only a few mineralization ages using the pitchblende U–Pb method have been published. These ages are commonly discordant and dispersed for abundant inclusions and an open U–Pb system. Zircon grains after strong hydrothermal alteration are usually characterized by high common Pb contents, and their U–Pb isochron ages recorded the hydrothermal alteration event without interference of common Pb components. The Hengjian gray/grayish-green granite porphyry experienced strong alteration by hydrothermal fluids during the pervasive uranium mineralization in the Xiangshan uranium ore field. Uranium mineralization in the Hengjian deposit may had different stages, and strong hydromicatization alteration occurred at a relatively early stage. Their altered zircon U–Pb isochron ages possibly represent relatively early mineralization age of the Xiangshan uranium deposits. Altered zircon grains from the Hengjian granite porphyry were analyzed using the secondary ion mass spectrometry (SIMS) U-Pb method in this study, and U–Pb isochron ages were measured to constrain the relatively early mineralization age of the Hengjian uranium deposit.