Zircon U-Pb geochronology and geochemistry of granites in the Zhuguangshan complex, South China: Implications for uranium mineralization

• Published in: Lithos 2018-05, Vol.308-309, p.19-33
• Main Authors: Zhang, Long, Chen, Zhenyu, Li, Xiaofeng, Li, Shengrong, Santosh, M., Huang, Guolong
• Format: Article
• Language: English
• Subjects: Geochemical diversity; Geochemistry; The Zhuguangshan complex; U-bearing and barren granites; Uranium mineralization
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2018.02.029

The Zhuguangshan complex, composed of Caledonian, Indosinian, and Yanshanian granites, and Cretaceous mafic dykes, is one of the most important granite-hosted uranium producers in South China. Here we present LA-ICP-MS zircon U-Pb and hornblende 40Ar/39Ar geochronology and whole-rock and biotite geochemistry for the granites in this complex to evaluate the magmatism and its constraints on uranium mineralization. Samples collected from the Fuxi, Youdong, Longhuashan, Chikeng, Qiling, and Sanjiangkou intrusions yield zircon weighted 206Pb/238U ages of 426.7 ± 5.4 Ma, 226.4 ± 3.5 Ma, 225.0 ± 2.7 Ma, 152.2 ± 3.0 Ma, 153.9 ± 2.1 Ma, and 155.2 ± 2.1 Ma, respectively. A new Ar-Ar dating of the hornblende of the diabase from the Changjiang uranium ore field yields a plateau age of 145.1 ± 1.5 Ma. These results coupled with published geochronological data indicate that six major magmatic events occurred in the study area at 420−435 Ma, 225−240 Ma, 150−165 Ma, ~140 Ma, ~105 Ma, and ~90 Ma. Both U-bearing and barren granites occur in this complex, and they display differences in whole-rock and biotite geochemistry. The barren granites show higher Al2O3, CaO, TFMM, Rb, Zr, Ba, SI, Mg#, (La/Yb)N, and Eu/Eu*, but lower SiO2, ALK, Rb, DI, Rb/Sr, and TiO2/MgO than those of the U-bearing granites. Biotites in the U-bearing granites are close to the Fe-rich siderophyllite-annite end member with Fe/(Fe + Mg) ratios higher than 0.66, whereas those in the barren granites are relatively close to the Mg-rich eastonite-phlogopite end member with Fe/(Fe + Mg) ratios