In situ U-Pb, Sr and Nd isotopic analysis of loparite by LA-(MC)-ICP-MS

This work describes the in situ analysis of loparite [(Na,REE)Ti2O6], a perovskite group mineral with extremely low Rb/Sr ratios and high rare earth contents, by LA-(MC)-ICP-MS for the determination of U-Pb ages together with Sr and Nd isotopic composition. The reliability of these data were validated by analysis of a loparite standard by TIMS solution methods. Data are given for loparite from the Lovozero and Khibiny peralkaline complexes of the Kola Alkaline Province (Russia). For Lovozero loparite the Tera-Wasserburg intercept age for 15 loparites analysed is 373 +/- 11 Ma, and the weighted Pb-207 corrected Pb-206/U-238 age is 373 +/- 2 Ma. For Khibiny loparite, the intercept age for 5 loparites analysed is 375 +/- 10 Ma, and the weighted Pb-207 corrected Pb-206/U-238 age is 374 +/- 3 Ma. The common Pb compositions for Lovozero and Khibiny loparites are identical i.e, Pb-207/Pb-206 = 0.898 +/- 0.009 and 0.898 +/- 0.007, respectively. The Sr-87/Sr-86 initial ratios of Lovozero loparite range from 0.703552 to 0.703682 (av. 0.703611), and epsilon Nd (t(370)) from + 3.8 to + 4.4 (av. + 4.0). The Sr-87/Sr-86 initial ratios of Khibiny loparite range from 0.703560 to 0.703871, and epsilon Nd (t(730)) from + 4.0 to + 4.8. Our data indicate that in situ LA-(MC)-ICP-MS analysis of loparite provides accurate and precise estimates of the intrusion ages and isotopic composition of peralkaline rocks. (C) 2010 Elsevier B.V. All rights reserved.