Nano-SIMS analysis of Mg, Sr, Ba and U in natural calcium carbonate
Nano-SIMS analysis of Mg, Sr, Ba and U in natural calcium carbonate
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DOI：
10.2116/analsci.21.1091
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发表时间：
2005-09-01
影响因子：
1.6
通讯作者：
Sturchio, NC
中科院分区：
文献类型：
--
作者：
Sano, Y;Shirai, K;Sturchio, NC
Concentrations of minor (Mg and Sr) and trace (Ba and U) elements in four natural calcium carbonate samples were first analyzed by inductively coupled plasma mass spectrometry (ICP-MS) after chemical dissolution and calibrated against a standard dolomite. Their homogeneities were checked by in situ laser ablation (LA) ICP-MS with 10 - 20 spots. The carbonate samples were measured by using a high lateral resolution secondary ion mass spectrometer (Nano-SIMS NS50). A similar to 4 nA O- primary beam was used to sputter a 5-6-mu m diameter crater on the sample surface, and secondary positive ions were extracted for mass analysis using an accelerating voltage of 8 kV and a Mattauch-Herzog geometry. A multi-collector system was adjusted to detect Mg-26(+), Ca-43(+), Sr-88(+), Ba-138(+), (UO+)-U-238-O-16 and (UO2+)-U-238-O-16 ions at the same time. A resolving power of 2500 - 5000 at 10% peak height was attained by an entrance slit set at 40 mu m, and each exit slit at 50 pm with adequate flat-topped peaks. The observed Mg-26/Ca-43, Sr-88/Ca-43, Ba-138/Ca-43 and (UO2)-U-238-O-16/Ca-43 ratios agreed well with those measured by LA-ICP-MS. Foraminifera shells were analyzed at 5 - 6 mu m scale by Nano-SIMS. There was a large variation of the Mg/Ca ratios, up to +/- 38%, even in a single fragment of the shell, suggesting that although the ratios provide a useful paleoceanographic proxy at bulk scale, they may reflect a more complex pattern at
