Combining microstructural analysis and in situ apatite−zircon U−Pb LA-ICP-MS to date fluid flow in world-class orogenic gold deposits: A case study from Oko West, Guyana

Determining the timing of mineralization in orogenic gold systems is a major challenge, given the difficulty of constraining fluid flow events and linking them to gold enrichment. However, it is critical for assessing whether world-class gold deposits result from a single mineralizing event or a multi-stage Au mobilization. In Paleoproterozoic settings, minerals suitable for precise dating of fluid flow are rare, and relying solely on intrusion-related geochronology may prove insufficient. In this context, combining detailed microstructural analysis with petrochronological data provides valuable insights into the tectonic and metallogenic evolution of deposits. In situ U−Pb dating was conducted on both zircon and apatite to investigate the timing of magmatism, deformation, and gold mineralization at Oko West, Guyana. Zircon and apatite ages from intrusive bodies indicate a magmatic event at ca. 2125 Ma, with apatite yielding the same age as that of zircon. Interpretation of the apatite U−Pb data set from mineralized volcano-sedimentary rocks was integrated with microstructural constraints on deformation and fluid flow. Apatite associated with metamorphic fluids and gold-bearing sulfidation records two successive stages at ca. 2100 Ma and ca. 2065 Ma, respectively. The clear temporal gap between the intrusion and the second mineralization stage supports the interpretation of at least two distinct geological events, the latter associated with post-magmatic gold mobilization. These results highlight the suitability of apatite U−Pb geochronology for resolving multi-stage gold deposition during the Rhyacian.