Uranium is the “grain” that fuels the development of the nuclear industry. In recent years, China’s newly discovered uranium resources have primarily come from sandstone-type uranium deposits in the north. Recently, reporters learned that Researcher Li Ziying, Chief Scientist of the China National Nuclear Corporation and a researcher at the Beijing Institute of Geology for the Nuclear Industry, along with her research team, has proposed a brand-new theory of sandstone uranium mineralization—the “seepage-driven sandstone uranium mineralization theory.” This theory holds promise as a key to expanding China’s “uranium granary” from the basin margins toward the basin center, from shallow to deep levels, and from gray sedimentary sandstones to red sedimentary sandstones.

According to the type of rock containing uranium, China’s uranium resources can be broadly classified into four main types: sandstone-type, granite-type, volcanic-rock-type, and carbon-siliceous shale-type. Among these, the northern part of China is predominantly characterized by sandstone-type uranium deposits, while the southern region is mostly home to hard-rock-type uranium deposits.

Previously, the conventional theory of sandstone-hosted uranium mineralization held that uranium-bearing, oxygen-rich surface waters, after seeping underground, would precipitate into ore deposits at the redox interface. This theory was once regarded as the “compass” guiding uranium exploration efforts in China’s sandstone-type uranium deposits and played a crucial role in exploration practices in basins such as Ili and Tuha in China.

According to traditional theory, the target strata for ore exploration are often located in gray sandstone layers, with exploration areas primarily concentrated along basin margins and at shallow depths. However, the conventional sandstone uranium mineralization theory has certain limitations when it comes to guiding and interpreting uranium mineralization processes in red-brown sedimentary sandstone formations.

Are the ore-forming mechanisms of uranium deposits in red sandstones still unclear? Can mineralization occur in the middle and deep parts of basins? With these questions in mind, Li Ziying and her team conducted a systematic study and detailed analysis of the typical Hadatu sandstone uranium deposit within the Cretaceous red formations of the Erlian Basin, drawing on solid domestic and international research data. They developed a new theory of uranium mineralization in sandstones driven by the “seepage” of uranium-rich, organic-matter-rich fluids from deep underground: Specifically, deep-seated fluids containing organic matter carry uranium with them. Under the driving forces of deep-seated pressure and elevated temperatures, these fluids seep upward along fractures and other pathways into shallow sandstone layers. As physical and chemical conditions—such as temperature, pressure, pH, and oxidation state—change, the uranium carried by the deep-seepage fluids precipitates and concentrates in favorable reservoir spaces, ultimately forming uranium deposits.

According to this theory, exploration geologists have conducted uranium exploration activities in basins such as the Ordos, Tarim, Erlian, and Qaidam, achieving remarkable exploration results. For instance, they have discovered sandstone uranium deposits at a depth of nearly 1,400 meters in the southern part of the Ordos Basin, marking a significant breakthrough in both exploration depth and uranium resource potential. Moreover, new uranium deposits have been identified in younger geological formations—including the Pliocene and even the Quaternary—in basins like Qaidam and Tarim, opening up promising new prospects for future exploration. Mr. Bolak, Chairman of the International Uranium Resources Group, believes that this theory represents a novel theoretical model for sandstone uranium deposits and holds great significance for mineral exploration. Notably, countries such as Uzbekistan have already adopted this theoretical model to guide their exploration efforts.