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This paper is the first to report a Pb–Pb and U–Pb analytical method at a sub-micron scale using a NanoSIMS equipped with the new radio-frequency (RF) ion source. The RF ion source can generate a high-density primary beam to improve spatial resolution. A focused Gaussian beam of ∼450 pA with a diameter of ∼480 nm was utilized, significantly smaller in size than the 1.7 μm beam with the same current generated by the conventional duoplasmatron source. However, the high-density primary beam causes a more significant depth effect. Thus, a larger raster area (10 × 10 μm2) is selected to eliminate the mass fractionation caused by the depth effect. Other settings and data processing were similar to previous methods with a Duo source. Zircon standard M257 and baddeleyite standard Phalaborwa yielded 207Pb/206Pb ages of 547 ± 30 Ma and 2058 ± 13.8 Ma, respectively. These results agree well with the reference age values within analytical uncertainties. Using zircon Qinghu as a standard, zircon M257 and 91500 yielded U–Pb ages of 567.7 ± 6.8 Ma and 1056 ± 15 Ma, respectively, consistent with the recommended values within the analytical uncertainties. Three 4–5 μm zirconolite grains from the lunar meteorite Northwest Africa 8127 (NWA 8127) gave Pb–Pb ages of 3201 ± 25 Ma, 3174 ± 6 Ma and 3170 ± 14 Ma. One grain shows a variation of Pb/Pb age corresponding to the sub-micron scale distribution of U and Pb, probably due to the heavy impact on the moon. This technique is the first reported submicron Pb–Pb and U–Pb dating, which can be widely applied for sub-micron Pb–Pb and U–Pb dating for the tiny Zr-rich minerals from extraterrestrial samples.

The partition coefficient of zircon/melt (Dzircon/melt) is a crucial parameter to obtain the chemical compositions of the parent melts from which the zircons crystallized, especially when we have no rock record and only relict zircons left (such as Hadean Earth, lunar breccia, and regolithic martian meteorites). However, the partition coefficients in the literature exhibit a large range, up to several orders of magnitude. A main cause for this discrepancy is heterogeneity of zircon's chemical composition at the submicron to micron scale, which requires an analytical method with a very high spatial resolution. Here we report trace element variations of P, Ti, Y, Ce, Sm, Ho and Lu across the interface between synthetic zircon and co-existing silicate melt measured at the submicron to micron scale with a NanoSIMS. The trace element composition profiles were calculated using SIMS image processing software to improve the spatial resolution close to the probe size scale (∼800 nm, 80 pA O−). The analytical precision varied from 5 to 30% (1SD) depending on the concentrations of the elements. The calculated partition coefficients show relatively small variations (e.g., Ce: 0.18–0.23, Ho: 9.2–9.9, Lu: 16–18) compared to those reported in the literature. Our study suggests that the large variation of zircon/melt partition coefficients reported in the literature may result from trace element variations in zircon zonation instead of reflecting two-phase equilibrium partitioning. Thus, zircon/melt partition coefficients must be measured by the high spatial resolution method. The general methodology could be applied to the determination of elemental distribution in other zoned minerals.

Water plays an important role in evolution of the Earth, Mars, Moon and other planets, with H isotopes used as a crucial tracer for fractionation processes and water reservoirs. In order to accurately and precisely measure water contents and D/H ratios of apatite and silicate glass with high lateral resolution, we carried out a long term measurement with a NanoSIMS 50L, with special consideration for the H background, calibration of water content and instrumental mass fractionation. A detection limit of

Reference materials play a crucial role in high accurate isotope and trace element analysis by secondary ion mass spectrometry, and they are used to calibrate instrumental fractionation of samples with various compositions. However, it is often a challenge to prepare natural or synthetic reference materials that are homogenous on a micron or even sub-micron scale. We report a novel method to synthesize homogeneous reference materials via sintering nano-crystals. Coarse-grained crystals (100–500 μm) of calcite have been grown from a starting material of 20–40 nm calcite powder at 1000 °C and 1 GPa for 24 h, which is ∼400 °C below the liquidus line of calcite under the same pressure. The non-molten sintering process and high temperature of the experiments ensure a homogeneous composition of the synthesized calcite. In situ analysis of 18O/16O ratios of the synthetic calcite with a Cameca NanoSIMS 50L revealed no detectable variation within the analytical uncertainty (0.5‰, 1SD), which was further confirmed using a Cameca IMS 1280 with a higher precision (0.1‰, 1SD). In addition, trace elements, Sr and P, are also homogeneous in the synthetic calcite. Another important advantage of this method is that the compositions of synthetic reference materials can be accurately and conveniently determined from the bulk starting materials using independent analytical techniques.

We report a new method of Pb-Pb dating for zircon and baddeleyite with a lateral resolution of

We report a modified procedure for separating Mg and Al from meteorites and terrestrial igneous rocks for high-precision analysis of Mg isotopes with multiple collector-inductively coupled plasma-mass spectrometry. The separating procedure was carried out in a single ion-exchange column filled with AG50W-X12 resin, and Mg was eluted with 1 M HNO3, followed by Al eluted with 4M HNO3. The modified procedure efficiently eliminates most matrix elements (except for Ni, Co, and Cu) with a recovery yield of Mg > 99%. Measurements of Ni-, Co-, and Cu-bearing simulation solutions revealed no detectable matrix effects. However, test runs demonstrated significant mass-dependent fractionation during the chromatographic process; consequently, a high recovery yield of Mg (>99%) is required to limit the deviation to less than 0.05‰. Furthermore, analysis of Mg standard solution with a wide range of concentrations demonstrated negligible deviation for samples with concentrations of 0.3–2.5 μg ml−1Mg relative to Mg standard solution concentrations of 1 μg ml−1Mg. The total procedure bank is less than 2 ng. The long-term reproducibility of instrumental measurements of Mg isotopes is ±0.05‰ for δ25Mg, ±0.10‰ for δ26Mg, and ±0.06‰ for δ26Mg* (2 SD, n = 211), based on analyzing five pure Mg standard solutions. Analysis of three chondrites and seven igneous rock standards showed ranges of δ26Mg(DSM3) from 0.02‰ to 0.30‰ for the former and from 0.03‰ to 0.30‰ for the latter. This method is simple and actionable.