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Geoscience ›› 2017, Vol. 31 ›› Issue (05): 990-1005.

• Petrology and Mineral Deposit • Previous Articles     Next Articles

The Magmatic Evolution and Its Constraints on Uranium Mineralization in the Xiaohuacha Uranium Deposit, Shaanxi Province

LIU Gang1,2(), LIU Jiajun1,2(), YUAN Feng1,2, ZHANG Shuai1,2, SHA Yazhou3, ZHANG Hongyuan1,2, WANG Gongwen1,2   

  1. 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
    2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
    3. No.224 Geological Party, Shaanxi Nuclear Industry Geological Bureau, Xi’an,Shaanxi 710024, China
  • Received:2017-04-13 Revised:2017-06-18 Online:2017-10-10 Published:2017-11-06

Abstract:

The Xiaohuacha uranium deposit is located in the northeastern section of the North Qinling Orogen. The uranium mineralization occurs within the assimilation and contamination area in the contact zone between the biotite granitic pegmatite and biotite plagioclase gneiss. To investigate the relationship between the granitic magma evolution and uranium mineralization, this paper presents detailed geochronological and geochemical studies of the granitoids. The results show that LA-ICP-MS zircon U-Pb ages of the Huichizi, Gaoshangou granites, and biotite pegmatites (uraniferous and non-mineralized zones) are (444±4.0) Ma, (422±0.82) Ma, (417±2.6) Ma, and (413±1.8) Ma, respectively. The granitoids are characterized by enrichment of large-ion lithophile elements (LILE), such as Rb, Ba, and K, but depletion of high field-strength elements (HFSE) such as Nb and Ta. High concentrations of Fe, Mg, and F in the uraniferous zone are interpreted to indicate chemical exchange between the pegmatitic magma and wall rocks in the assimilation-contamination area. The compositional heterogeneity in the individual biotite pegmatites is ascribed to the assimilation-fractional crystallization of pegmatitic magma. Interaction with the wall rocks in the contact zone triggers the destabilization of U-F complexes and precipitation of uraninite from the pegmatitic magma (ca.417 Ma) under favorable emplacement conditions. The assimilation of biotite plagioclase gneiss by pegmatitic magma during volatile saturation plays a main role in the formation of the Xiaohuacha uranium deposit.

Key words: zircon U-Pb dating, geochemical characteristic, pegmatite-hosted type uranium deposit, assimilation-contamination

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