Geochemical Journal, Vol. 52 (No. 1), pp. 69-74, 2018
Morihisa Hamada,1* Jun-Ichi Kimura,1 Qing Chang,1 Takeshi Hanyu,1 Takayuki Ushikubo,2 Kenji Shimizu,2 Motoo Ito,2 Takahiro Ozawa3 and Hikaru Iwamori1,3
1Department of Solid Earth Geochemistry, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
2Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 200 Monobe-otsu, Nankoku, Kochi 783-8502, Japan
3Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Meguro-ku, Tokyo 152-8551, Japan
(Received April 13, 2017; Accepted July 28, 2017)
We report a high-precision 206Pb-based lead isotope composition of olivine-hosted melt inclusions in basaltic rocks from Rarotonga Island, Polynesia, in the southern Pacific, using femtosecond laser ablation (FsLA)-multiple Faraday collector-inductively coupled plasma-mass spectrometry (MFC-ICP-MS). This improved method enables high-precision analysis of Pb isotopes from low-Pb (≤10 ppm) melt inclusions with a crater size of ∼30 μm in diameter and depth. The small crater size allows for further analysis of major and trace elements from the same melt inclusions using FsLA-sector field (SF)-ICP-MS. Using Pb isotope ratios of two olivine-hosted melt inclusions, we suggest that the mantle source beneath Rarotonga Island is heterogeneous. Such identification becomes possible owing to high-precision in situ analysis of Pb isotopes in melt inclusions and application of statistical approaches such as Independent Component Analysis to the analytical data.
Key words: Rarotonga Island, ocean island basalt, Pb isotope, laser ablation ICP-MS, Independent Component Analysis