Insights on the formation of the Warrego Au-Cu-Bi deposit from monazite and xenotime U-Pb dating: A new mineralization event in the Tennant Creek province

The Warrego Au-Cu-Bi deposit is the largest deposit in the Tennant Creek province, but despite its size, the age of mineralization is still uncertain. Previous geochronological studies in the Tennant Creek province have focused on several other deposits, which have yielded a large range in U-Pb ages for Au-Cu-Bi mineralization between 1860 and 1650 Ma. In this study, we combine in situ LA-ICP-MS monazite and xenotime U-Pb geochronology with backscattered-electron imaging and EPMA chemistry to constrain the age of ore formation at Warrego. Textural relationships of REE-phosphates confirm their contemporaneous growth with gold and Cu-Bi sulfides and sulfosalts. The analyses reveal the presence of multiple REE phosphate phases such as monazite, xenotime, rhabdophane and other accessory minerals. Monazite in all samples exhibits low Th and elevated total REE oxide contents, characteristic of low-temperature (<350°C) hydrothermal formation. Xenotime is intergrown with monazite and both minerals show coherent isochrons on Concordia diagrams. The rhabdophane data is strongly discordant but can be easily identified by filtering analyses for Sr < 100 ppm. Populations of concordant U-Pb analyses reveal two distinct mineralizing events at ca. 1830 Ma and ca. 1710 Ma. The older event overlaps with early Tennant Creek Supersuite magmatism, whereas the younger represents a previously unrecognized episode of Au-Cu-Bi mineralization in the province, temporally linked to the emplacement of the nearby Warrego Granite. These findings indicate that the Tennant Creek Mineral Field experienced multiple mineralizing or reworking events, consistent with existing IOCG models that invoke prolonged, episodic hydrothermal activity as a key ingredient of ore deposit formation. The identification of a ca. 1710 Ma event introduces a new temporal target for exploration, expanding the potential for Au-Cu-Bi discovery across the province.