Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (1): 368-383.DOI: 10.13745/j.esf.sf.2024.1.7

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Novel metallogenic model of sandstone-type uranium deposits: Mineralization by deep organic fluid

LIU Chiyang1(), ZHANG Long2, HUANG Lei1, WU Bailin1, WANG Jianqiang1, ZHANG Dongdong1, TAN Chengqian2, MA Yanping2, ZHAO Jianshe3   

  1. 1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China
    2. School of Earth Sciences and Engineering, Xi’an Shiyou University, Xi’an 710065, China
    3. College of Chemistry & Materials Science, Northwest University, Xi’an 710069, China
  • Received:2024-01-08 Revised:2024-01-24 Online:2024-01-25 Published:2024-01-25

Abstract:

Most existing metallogenic models maintain that sandstone-type uranium (U) deposits are formed by infiltration of exogenous uranium carried by near-surface oxygenated waters from erosion source areas into basins. However, this study finds that these traditional models fail to explain the geological evolution, geomorphological characteristics, and mineralization of sandstone-type uranium deposits in eastern Yimeng Uplift, northern Ordos Basin. The key issue is the material source of uranium mineralization. Geochemical analysis of representative minerals from this area, including coffinite (formed in a strongly reducing environment) and its associated minerals, reveal the existence of two distinct uranium mineralization environments: low-salinity meteoric waters and medium-high-salinity hydrothermal fluids, and primary uranium mineralization occurred less than 80 Ma. Considering the U-rich source rocks of coal-bearing strata in the basin, the enormous dissipation of natural gas, and the widespread distribution of various hydrocarbon alteration products and condensate oil traces related to the dissipation of mature coal-type gas in the Yimeng Uplift, a novel metallogenic model of large uranium deposits is proposed based on comprehensive simulation experiments and testing analysis. According to the new model, the uranium source originates from deep U-rich coal strata in the middle of the basin, where dissolved gases from thermal fluids migrate and dissipate towards higher elevations in the eastern Yimeng Uplift, extracting and carrying uranium from the source rock and uranium-rich strata along the way to shallower layers to cause sparry calcite and coffinite to precipitate as temperature/pressure decreases; meanwhile along with the near-surface, low temperature mineralization, massive exsolved natural gas creates a reducing environment for the preservation of uranium deposits. This new model of uranium mineralization opens up new horizons for uranium exploration in terms of exploration approaches and domains, and strengthens the scientific basis for polymineralization involving different mineral (metallic, non-metallic) and energy (hydrothermal, hydrocarbon) types, as well as prediction and evaluation of such polyminealization occurrences.

Key words: novel uranium metallogenic model, deep uranium source, natural gas dissipation, hydrothermal mineralization, northern ordos basin, Yimeng uranium district

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