Geochemical characteristics and geological significance of uranium-rich granites in Lincang area
TIAN Jian-Min1(), XU Zheng-Qi1,2(), YIN Ming-Hui1, LI Tao1, SUN Kang3
1.College of Geoscience, Chengdu University of Technology, Chengdu 610059, China 2.Sichuan Key Laboratory of Geoscience and Nuclear Technology, Chengdu 610059, China 3.Mechanical Design Sixth Design and Research Institute Co., Ltd., Zhengzhou 450000, China
Petrographic and geochemical study and U-Pb dating of uranium-rich granite bodies in Lincang area were carried out for Shuangjiang 701 and Fengqing 901 uranium mines, with the purpose of exploring the relationship between petrogenesis type, diagenetic tectonic background and uranium mineralization. The results show that Lincang uranium-rich granite body has high Si (up to 90.11%, averaging 71.6%), rich alkali, high potassium and high Ca, thus belonging to high Al and high potassium calcium alkaline series rocks. U-Pb zircon dating yielded 214±12 Ma, and thus Lincang uranium-rich granite body was formed in Late Indochina. Rare earth elements show a slightly rightward "V" shape, with obvious fractionation of light and heavy rare earth elements (w(LREE)/w(HREE) 7.26 on average), obvious negative Eu anomaly (δEu=0.28 ~ 0.49), relative enrichment of Rb, U and Th, and relative loss of Ba, Nb, Sr, Ti and Eu. Comprehensive analysis shows that Lincang uranium-rich granite belongs to S-type granite with obvious differentiation, which must have originated from melting of upper crust material and was formed in a mountain-building and rift environment in late collision, belonging to the simultaneous collision of granite related to the Lancang River collision zone. Its high content of uranium provided part of the uranium source for the uranium mineralization process. Uranium elements were transported to the vicinity of the fault fracture zone and was enriched to form granite-type uranium deposits by leaching.
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