@article{fdi:010088895,
  title = {{S}equential extractions versus alpha autoradiography : mutually complementary for the identification of {U}- and {R}a-bearing minerals in mine tailings},
  author = {{B}illon, {S}. and {S}avoye, {S}. and {S}ardini, {P}. and {G}{\'e}rard, {M}artine and {B}eaucaire, {C}. and {C}oreau, {N}. and {D}escostes, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}o assess the long-term stability of uranium in mill tailings, the identification of radionuclide (238{U} and daughters)-bearing minerals is the first step. {A} combination of sequential extractions and alpha autoradiography (coupled to scanning electron microscopy) seems powerful for this purpose. {T}ailings coming from uranium mine sites in {G}abon are composed mainly of quartz, feldspars, mica/illite, chlorite and kaolinite and many accessory minerals (siderite, {F}e and {T}i oxides, sulfate- or sulfide-bearing minerals, uraninite, zircon, etc.). {U}ranium was detected in minerals inherited from the ore, such as uraninite enclosed in quartz or bitumen and zircons (up to 18 wt% of {U}), and in newly formed minerals, such as siderite (up to 1.7 wt% of {U}) and {T}i and {F}e oxides (up to 3.5 wt% {U}). {S}equential extractions indicate that 40 % of {U} is unextractable, which indicates {U} is trapped in an efficient way in the tailings, probably in zircon and in uraninite enclosed in quartz grains. {U} was mainly released during the acetate extraction step targeting the {T}i and {F}e oxides and siderite and during the {H}2{O}2 step that attacked the bitumen, allowing the dissolution of enclosed uraninite. {B}a/{P}b sulfates, which are well known to incorporate 226{R}a through solid solution mechanisms, are identified as the main trap of 226{R}a in the studied tailings. {B}arite, the predominant sulfate, occurs in two populations: an inherited one under grain form and a newly formed one under fibrous habits. {S}ome fibrous habits are sometimes observed at the inherited barite grain surface, corresponding to barite recrystallization. {U}sing alpha autoradiography, amounts of 226{R}a ranging from 2 to 30 ppm were estimated in these sulfate minerals (corresponding to specific activities from 70 k{B}q to 1 {MB}q per gram of sulfate grain). {B}arite, the predominant and 226{R}a richest sulfate mineral (30 ppm), is quite insoluble. {O}nly the strongest leaching steps partially dissolved it; 40 % of 226{R}a remained unextractable, highlighting its low mobility in environmental conditions.},
  keywords = {{A}utoradiography ; {S}equential extraction ; {U}ranium ; {R}adium ; {T}ailings ; {GABON}},
  booktitle = {},
  journal = {{J}ournal of {G}eochemical {E}xploration},
  volume = {257},
  numero = {},
  pages = {107368 [17 ]},
  ISSN = {0375-6742},
  year = {2024},
  DOI = {10.1016/j.gexplo.2023.107368},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088895},
}