Characteristics of uranium- bearing minerals in Yangzhuang granite porphyry in the Xuemistan metallogenic belt and its significance for uranium metallogenesis
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    Abstract:

    The Yangzhuang granite porphyry is spatially closely related to the Baiyanghe uranium deposit and was strongly transformed after its formation. This study carried out detailed petrographic and petrogeochemical studies on this granite porphyry. The results show that the Yangzhuang granite porphyry is alkali- rich (alk:8. 40%~8. 97%),especially potassium- rich (K2O:2. 74%~4. 10%),aluminum- rich (Al2O3:12. 32 %~13. 54%),low calcium (CaO:0. 23%~1. 61%),magnesium- depleted (MgO:0. 04%~0. 11%),extremely phosphorus- depleted,high ΔOX (more than 1); significantly enriched in LILEs (such as K,Rb,Pb,etc. ) and U,Be,Mo,Nb,Ta elements, shows severe losses of Ba,Sr,Eu and other elements. The total amount of rare earth elements is 95. 22×10-6~121. 89×10-6. All samples showed a strong negative anomaly of Eu (δEu:0. 05~0. 11) with a seagull- type rare earth distribution,showing a characteristic of high differentiation. The Th/U ratio of granite porphyry is between 2. 9 and 11. 6 with large variation,indicating that the uranium of the rock may have been leached out. The covariation diagram of uranium with rare earth,zirconium,and niobium shows positive correlation,which suggests that when uranium was activated and migrated,the rare earth,zirconium,and niobium also underwent a certain degree of activation and migration. The results of the α- track etching experiments show that the etching tracks on the substrate are clear and concentrated,indicating that radioactive elements such as uranium and thorium are mainly concentrated in the mineral phase. Scanning electron microscopy and electron microprobe analysis results show that these uranium- bearing minerals are mainly zircon (UO2:0. 24%~0. 45%),manganocolumbite (UO2:0. 49%~0. 76%),thorite (UO2:1. 56%~2. 09%),bastnasite (UO2:0. 17 %~0. 3%) and xenotime (UO2:0. 08%). These minerals mostly show traces of modification. Common mineral structures are:eroded harbor- like structures,etching structureetc. The analysis suggests that the reason why the pitchblende of the Baiyanghe uranium ore is enriched with elements such as Zr,Nb,REE,Ti,and even W is related to the “genetic genes” of uranium minerals carried in the Yangzhuang granite porphyry.

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LI Guanglai, CHEN Guangxu, LIU Xiaodong, LI Chengxiang, WANG Guo, LIU Xiaobo, LIU Zhengyu, LONG Weikang.2020. Characteristics of uranium- bearing minerals in Yangzhuang granite porphyry in the Xuemistan metallogenic belt and its significance for uranium metallogenesis[J]. Acta Geologica Sinica,94(11):3404-3420

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History
  • Received:January 09,2020
  • Revised:March 26,2020
  • Adopted:
  • Online: October 30,2020
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