On the uranium source of North-eastern Jiangxi, South China

Dozens of uranium deposits and mineralization sites are distributed within the Mesozoic–Cenozoic volcanic rock - red bed belt of northeastern Jiangxi, mainly hosted by volcanic rocks, granite, metamorphic rocks and sandstone, and their uranium sources are subject to crustal mantle disputes. Iron isotope analysis, combined with previous geochronological and geochemical data, show that: (1) Four geological events were observed, which probably genetic related to uranium enrichment, namely, the development of uranium ore shoots were related to faults, the mineralization age span was large (148-47 Ma), the hydrothermal fluids were a mixture of atmospheric precipitation, magmatic water, and mantle fluid, and the uranium deposit surrounding rock is not selective. It is noteworthy that different stable isotope data often suggest a different origin mineralier, including meteoric water, magmatic fluids, and mantle-derived components, even within a single deposit. (2) Despite differing host rocks, the Zoujiashan and Yunji uranium deposits and the Yingtan-113, 364, and Tongboshan mineralization sites exhibit consistently positive δ⁵⁶Fe values ranging from 0 to +0.92‰. Collectively, the evidence disfavors a mantle-derived uranium source, instead pointing to the red beds as the more plausible origin. Mineralization model of "crustal source (red bed uranium source) - structural control - multi-stage hydrothermal superposition" was proposed: in arid and oxidizing environments, uranium containing minerals in the red layer were leached, and hydrothermal uranium deposits are formed by long-term coupling with mantle-derived reducing fluids through fault structures.

Funding: National Natural Science Foundation of China (42472130) and ECUT Research Development Fund (K20240017, K20240018).

Keywords: uranium deposit, iron isotopes, uranium source, northeastern Jiangxi, red beds