Abstract:

Julong,an is a large-sized mixed uranium and thorium deposit in the western Xiangshan ore field, Jiangxi Province. On
the basis of systematic geochemical analysis, this paper discusses distribution characteristics of both trace and major elements
associated with thorium mineralization in detail. The major elements of Th-rich samples are rich in calcium and phosphorus, and
characterized by Na2O>K2O. The mono-uranium mineralization is always developed in the early stage of alkali alteration, and the
thorium mineralization is mainly concentrated in the later stage of pitchblende-fluorite-hydromica alteration halo. The distribution
patterns of rare earth elements in wall rocks and mineralized samples are different. The thorium mineralization is highly associated
with rare earth elements, especially with the heavy ones. Trace elements such as Re, Y, Se, Lu are highly correlated with thorium
mineralization due to formation of associated sulfides and phosphates, such as xenotime.

Key words: thorium geochemistry, mixed uranium-thorium mineralization, isomorphism, Xiangshan ore field, Jiangxi Province