High spatial resolution analysis of Pb and U isotopes for geochronology by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS)

Anais da Academia Brasileira de Ciências

Bernhard Bühn¹  Márcio M. Pimentel¹  Massimo Matteini¹  Elton L. Dantas¹ 

[1] ,Universidade de Brasília Instituto de Geociências Brasília DF ,Brasil

关键词: geochronology;    U-Pb isotopes;    LA-MC-ICP-MS;    zircon;    age dating;    geocronologia;    isótopos U-Pb;    LA-MC-ICP-MS;    zircão;    datação;   

DOI  :  10.1590/S0001-37652009000100011

来源: SciELO

【 摘 要 】

Age determinations using the 235U and 238U radioactive decay series to the daughter isotopes 207Pb and 206Pb, respectively, using the mineral zircon (ZrSiO4), are widely used to decipher geological processes. A new method developed in the last couple of years, the laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), overcomes previous laborious sample preparation, and yields isotopic ratios and age data with a high spatial resolution of ten of microns. The present study describes the analytical set-up and data reduction process as presently applied at the Laboratory for Geochronology of the University of Brasília. It explores the precision and accuracy of the method by cross-analysing three international zircon standards. We arrive at a precision of 1.9 to 3.7% (2σ SD) and an accuracy of 0.6 to 3.8% (2σ SD) for and U isotopic ratios of the standards. We also apply the method to two natural zircon samples, which have previously been dated by other analytical methods. A comparison of the results show a good conformity of the age data,being whitin the error limits. The data demonstrate the great analytical potential of the method for rapid, precise and accurate U-Pb isotopic analyses on the micron scale.

【 授权许可】

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