%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Legros, H.
%A Mercadier, J.
%A Villeneuve, J.
%A Romer, R. L.
%A Deloule, E.
%A Van Lichtervelde, Marieke
%A Dewaele, S.
%A Lach, P.
%A Che, X. D.
%A Wang, R. C.
%A Zhu, Z. Y.
%A Gloaguen, E.
%A Melleton, J.
%T U-Pb isotopic dating of columbite-tantalite minerals : development of reference materials and in situ applications by ion microprobe
%D 2019
%L PAR00019213
%G ENG
%J Chemical Geology
%@ 0009-2541
%K Columbite-tantalite ; Niobium ; Tantalum ; U-Pb dating ; SIMS ; ID-TIMS ; Geochronology
%K COTE D'IVOIRE ; RWANDA ; CHINE ; FRANCE
%M ISI:000461651600006
%P 69-84
%R 10.1016/j.chemgeo.2019.03.001
%U https://www.documentation.ird.fr/hor/PAR00019213
%> https://www.documentation.ird.fr/intranet/publi/2019/04/010075481.pdf
%V 512
%W Horizon (IRD)
%X Columbite-tantalite group minerals are the most common Nb-Ta minerals. Columbite-tantalite is particularly suitable for U-Pb dating due to its high U and low common Pb contents. In situ isotopic dating of columbite-tantalite by LA-ICP-MS or SIMS requires certified reference material to properly account for potential matrix effects linked to substitutions between Nb and Ta and between Mn and Fe. Our study has two objectives: i) establish a database of reference materials for in situ U-Pb isotopic dating of columbite-tantalite minerals and ii) test the capability of SIMS to in situ U-Pb date columbite-tantalite minerals of different chemical composition. Tests of in situ U-Pb dating demonstrate that SIMS can easily be used to date columbite-tantalite minerals with errors and precisions overlapping the reference ID-TIMS age. There are, however, significant matrix effects for non-matching Nb-Ta-Fe-Mn compositions of sample and reference material. Matrix effects are highly correlated with the Ta/(Ta+Nb) ratio of columbite-tantalite, due to the significant difference in the atomic mass of Nb and Ta. The Mn/(Mn+Fe) ratio does not significantly contribute to the observed matrix effect as the two elements have similar atomic masses. The linear correlation between Ta/(Nb+Ta) and ((Pb-206/U-238)(SIMS)/(Pb-206/U-238) (ID-TIMS)) obtained for columbite-tantalite minerals of known ID-TIMS age demonstrates that the SIMS matrix-effect can be properly accounted for by using the chemical composition as determined by EMPA. The ability to measure Pb-204 by SIMS also allows the use of reference materials with a small common lead contribution and to calculate accurate and precise ages for columbite-tantalite minerals with contributions of common lead.
%$ 064