Legros H., Mercadier J., Villeneuve J., Romer R. L., Deloule E., Van Lichtervelde Marieke, Dewaele S., Lach P., Che X. D., Wang R. C., Zhu Z. Y., Gloaguen E., Melleton J. (2019). U-Pb isotopic dating of columbite-tantalite minerals : development of reference materials and in situ applications by ion microprobe. Chemical Geology, 512, p. 69-84. ISSN 0009-2541.
Titre du document
U-Pb isotopic dating of columbite-tantalite minerals : development of reference materials and in situ applications by ion microprobe
Année de publication
2019
Auteurs
Legros H., Mercadier J., Villeneuve J., Romer R. L., Deloule E., Van Lichtervelde Marieke, Dewaele S., Lach P., Che X. D., Wang R. C., Zhu Z. Y., Gloaguen E., Melleton J.
Source
Chemical Geology, 2019,
512, p. 69-84 ISSN 0009-2541
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.
Plan de classement
Géologie et formations superficielles [064]
Description Géographique
COTE D'IVOIRE ; RWANDA ; CHINE ; FRANCE
Localisation
Fonds IRD [F B010075481]
Identifiant IRD
PAR00019213
