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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Constraints of the geochemical characteristics of apatite on uranium mineralization in a uraninite-rich quartz vein in the Haita area of the Kangdian region, China

Minghui Yin, Zhengqi Xu, Hao Song, Chengjiang Zhang, Suheng Zhang, Jianmin Tian, Hu Guo
Geochemical Journal, Vol. 55, No. , P. 301-312, 2021


Uraninite is commonly smaller than 1 mm and widespread in felsic or alkaline igneous rocks as accessory minerals. However, abundant coarse-grained euhedral uraninites, up to 1 cm in size, are intergrown with sphene, apatite, zircon, and some other accessory minerals in a quartz vein from the Haita area of the Kangdian region, China. Although previous studies have examined uraninite in detail, the genesis of the uraninite-rich quartz vein remains controversial. In this study, we investigate the relationships among euhedral single-particle apatite (ApA), aggregated apatite (ApB), and uraninite in a uraninite-rich quartz vein. TESCAN integrated mineral analysis, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry were used to investigate the nature of the ore-forming fluids of U mineralization. The two types of apatites have similar major element compositions and rare earth element patterns, whereas trace elements, such as Mn, U, and Cu, exhibit different characteristics, indicating a two-stage evolution of the ore-forming fluids. In addition, both types of apatite are fluorapatite, indicating high F concentrations in the ore-forming fluid, which favors U mobility. Changes in the concentrations of multivalent elements (such as Mn, Eu, and Ce) in the two types of apatite indicate that a slow increase in the oxygen fugacity promotes megacrystalline uraninite formation. A significant increase in the U concentrations from ∼46.56 ppm in the ApA to ∼7,169.12 ppm in the ApB likely represent an enrichment of U in the fluid. This study provides a new geochemical basis for understanding the mechanism of megacrystalline uraninite formation.


apatite, geochemistry, oxygen fugacity, ore-forming fluid, uraninite

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