Genesis of the leucogranite-hosted uranium deposit in Gaudeanmus area, Central Damara Belt, Namibia, constrained by mineralogical, and in-situ U-Pb isotopic signatures of uraninite

In Namibia, there are abundant uranium resources of different types, and therein, leucogranite-hosted uranium deposit is one of the most important. The Gaudeanmus deposit, located in southeast of the Rössing deposit, is a typical leucogranite-hosted uranium deposit where uranium dominantly exists in independent uranium minerals, or is sparsely contained in other minerals as isomorphism, according to petrologic and mineralogic identification and EPMA analysis. However, the genetic relationship between leucogranite crystallization and uranium mineralization, and the precise role of magmatism versus later hydrothermal processes, remain unresolved scientific issues. This study aims to address these questions. The uranium minerals are mainly uraninite as well as a few thoriumurite, coffinite, brannerite, betafite, uranothorite, pitchblende and uranophane. The Gaudeanmus uranium deposit is mainly controlled by tectonics, leucogranite and strata, the uranium deposits are mainly controlled by tectonics, leucogranite and strata. Tectonic deformation created domes, folds and fractures that provided space and fluid pathways for mineralization. D- and E-type leucogranites supplied uranium through partial melting and crystallization, while the Karibib and Kuiseb Formations acted as favorable host strata for ore accumulation. and late hydrothermal solution has promoted locally the enrichment of uranium. The ore bodies mainly occur at bend of folds, on edge of domes and in between fault transformations (such as transitions, expansions, etc.), where there is a sufficient space for uranium mineralization. The Welwitschia regional fault provided a channel for activation and migration of uranium. The mineralized leucogranite contains specific property that only D and E types of leucogranite contains uranium, but other types of leucogranite and Salem-type granite mineralization does not, and the mineralized leucogranite usually intruded into the Karibib and Kuiseb formations in Gaudeanmus area. The anaphasis fluid was helpful for superposition enrichment for uranium mineralization. LA-ICP-MS in-situ U-Pb dating of zircon and uraninite shows that the diageneic age is 499 ± 30 Ma and the main mineralization age of uranium is 502 ± 3 Ma, which indicated that the main mineralization age of uranium is basically consistent with the diagenic age of leucogranite. The uranium at the main metallogenic stage of the leucogranite-hosted uranium deposit came from the uranium-rich pre-Damara basement, and the uranium at the hydrothermal superposition transformation stage might come from the primary uranium mineral itself. The mineralization of leucogranite-hosted uranium deposits can be roughly divided into three periods: crystalline differentiation of primary magma, superimposed transformation of late hydrothermal fluid and epigenetic oxidation. Based on this, a four-stage, three-period uranium mineralization model has been established. Unlike previous studies that only outlined the model conceptually, this study integrates new mineralogical evidence and in-situ U-Pb ages of uraninite and zircon, demonstrating that magmatism and mineralization were contemporaneous, thus refining the genetic model.