Application of inductively coupled plasma quadrupole mass spectrometry for the determination of monazite ages by lead isotope ratios

Journal of the Brazilian Chemical Society

Instituto de Radioproteção e Dosimetria, Rio de Janeiro-RJ, Brazil¹  Aronne, Cláudia C.¹  Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro, Brazil¹  Godoy, José Marcus¹  Godoy, Maria Luiza D. P.¹ 

关键词: inductively coupled plasma mass spectrometry (ICP-MS);    lead dating;    monazite;   

DOI  :  10.1590/S0103-50532007000500014

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

In order to evaluate the applicability of inductively coupled plasma quadrupole mass spectrometry to the determination of Pb/Pb, U/Pb and Th/Pb ages of monazite, studies were carried out initially applying lead atom ratio reference standards (NIST SRM 981 and 982). Further, the optimized methodology was applied to monazite sands from three different sites, Sugar Loaf Hill (Rio de Janeiro city), Buena (Rio de Janeiro state) and Black Sands Beach (Guarapari, Espirito Santo state); the obtained mean ages, (581 ± 21)Myears, (552 ± 32)Myears and (535 ± 3)Myears, respectively, are in agreement with the literature values for zircon and monazite samples from the same sites. Single grain Th/Pb ages were also determined for the monazite sample from Black Sands beach, nine grains were analyzed and the mean value, (530 ± 26)Myears, is in agreement with the value obtained with bulk samples. Finally, the method was applied to a thorianite sample from Amapá state and the observed Th-Pb, U-Pb and Pb-Pb ages obtained were (2.15 ± 0.05)Gyears, (2.03 ± 0.01)Gyears anda (2.044 ± 0.006)Gyears respectively, with a mean value of (2.08 ± 0.07)Gyears. This value is coherent with the (2.08 ± 0.02)Gyears age of the Bacuri complex, Amapá, reported in the literature.

【 授权许可】

Unknown