测试项目：Nd同位素
测试对象：磷灰石、榍石、独居石
测试周期：来电详询
送样要求：1、样品靶或岩石薄片，薄片尺寸参见原位主微量元素分析要求；2、样品Nd含量大于400ppm；3、样品贫Sm，Sm/Nd含量比低于1 ，大于此范围的样品请提前告知。
完成标准：测试内精度及标样外精度和准确度确保达到国际水平。
方法描述：
两个天然磷灰石标样，Durango和MAD作为未知样品监控微区原位磷灰石Nd同位素校正方法的可靠性。Durango和MAD的化学组成和Nd同位素组成参见Xu et al .（2015）。
两个天然榍石标样，MKED1和SP-Ttn-01作为未知样品监控微区原位榍石Nd同位素校正方法的可靠性。MKED1的化学组成和Nd同位素组成参见Spandler et al. (2016)。
一个天然独居石标样GBW44069和一个天然榍石标样MKED1作为未知样品监控微区原位独居石Nd同位素校正方法的可靠性。GBW4409的化学组成和Nd同位素组成参见Xu et al .（2015）。
Two natural apatite megacrysts, Durango and MAD, were used as the unknown samples to verify the accuracy of the calibration method for in situ Nd isotope analysis of apatites. The chemical and Nd isotopic compositions of Durango and MAD have been reported by Xu et al . (2015).
Two natural titanite megacrysts, MKED1 and SP-Ttn-01, were used as the unknown samples to verify the accuracy of the calibration method for in situ Nd isotope analysis of titanite. The chemical and Nd isotopic compositions of MKED1 have been reported by Spandler et al. (2016).
One natural monazite megacrysts GBW44069 and another natural titanite megacrysts MKED1 were used as the unknown samples to verify the accuracy of the calibration method for in situ Nd isotope analysis of monazite. The chemical and Nd isotopic compositions of GBW44069 have been reported by Xu et al . (2015).
References
Xu, L. , Hu, Z.C, Zhang, W., Yang, L., Liu, Y.S., Gao, S., In situ Nd isotope analyses in geological materials with signal enhancement and non-linear mass dependent fractionation reduction using laser ablation MC-ICP-MS. Journal of Analytical Atomic Spectrometry , 2015, 30(1), 232-244.
Hu, Z.C., Zhang, W., Liu, Y.S., Gao, S., Li, M., Zong, K.Q., Chen, H.H., Hu, S.H., 2015. “Wave” signal-smoothing and mercury-removing device for laser ablation quadrupole and multiple collector ICPMS analysis: application to lead isotope analysis. Analytical Chemistry, 87(2), 1152–1157.
Carl Spandler,Johannes Hammerli. MKED1:A new titanite standard for in situ analysis of Sm-Nd isotopes and U-Pb geochronology[J].Chemical Geology,2016,425(1):110-126.
Zhang W., Hu Z.C., Liu Y.S. (2020). Iso-Compass: new freeware software for isotopic data reduction of LA-MC-ICP-MS. J. Anal. At. Spectrom., 2020, 35, 1087–1096.
方法描述：
23.1 LA- MC- ICP-MS 微区原位Nd同位素比值测试
微区原位Nd同位素比值测试在武汉上谱分析科技有限责任公司利用激光剥蚀多接收杯电感耦合等离子体质谱（LA-MC-ICP-MS）完成。激光剥蚀系统为Geolas HD（Coherent，德国），MC-ICP-MS为Neptune Plus（Thermo Fisher Scientific，德国）。激光剥蚀系统使用氦气作为载气。少量的氮气被加入到ICP以提高Nd同位素的测试信号（Xu et al . 2015）。分析采用单点模式，激光的束斑大小和剥蚀频率根据样品的Nd信号强度调节，一般为32-90 μm和4-10 Hz。激光能量密度固定在~8.0 J/cm 2 。分析过程配备了信号平滑装置，可以提高信号稳定性和同位素比值测试精密度（Hu et al . 2015）。质谱仪Neptune Plus配备9个法拉第杯，可同时静态接收 142 Nd, 143 Nd, 144 Nd, 145 Nd, 146 Nd, 147 Sm, 148 Nd和 149 Sm信号。 143 Nd/ 144 Nd同位素仪器质量分馏校正通过指数法则校正，校正因子利用 146 Nd/ 144 Nd = 0.7219估算获得。 144 Sm对 144 Nd的干扰校正通过监控 149 Sm的信号，并选择 144 Sm/ 149 Sm = 0.2301。 144 Sm/ 149 Sm的仪器质量分馏校正通过归一化到无干扰的 147 Sm/ 149 Sm，并选择 147 Sm/ 149 Sm = 1.08680。详细的分析方法校正描述请参考（Xu et al . 2015）。全部分析数据采用专业同位素数据处理软件“Iso-Compass”进行数据处理（Zhang et al., 2020）。两个天然磷灰石标样，Durango和MAD作为未知样品监控微区原位磷灰石Nd同位素校正方法的可靠性。Durango和MAD的化学组成和Nd同位素组成参见Xu et al .（2015）。
两个天然榍石标样，MKED1和SP-Ttn-01作为未知样品监控微区原位榍石Nd同位素校正方法的可靠性。MKED1的化学组成和Nd同位素组成参见Spandler et al. (2016)。
一个天然独居石标样GBW44069和一个天然榍石标样MKED1作为未知样品监控微区原位独居石Nd同位素校正方法的可靠性。GBW4409的化学组成和Nd同位素组成参见Xu et al .（2015）。
23.2 In-situ Nd isotope analysis by LA-MC-ICP-MS
In situ Nd isotope analysis was performed on a Neptune Plus MC-ICP-MS (Thermo Fisher Scientific, Bremen, Germany) equipped with a Geolas HD excimer ArF laser ablation system (Coherent, Göttingen, Germany) at the Wuhan Sample Solution Analytical Technology Co., Ltd, Hubei, China. In the laser ablation system, helium was used as the carrier gas within the ablation cell and was merged with argon (makeup gas) after the ablation cell. Small amounts of nitrogen were added to the argon makeup gas flow for the improvement of sensitivity of Nd isotopes (Xu et al . 2015). The spot diameter ranged from 32 to 90 μm dependent on Nd signal intensity. The pulse frequency was from 4 to 10 Hz, but the laser fluence was kept constant at ~8 J/cm 2 . A new signal-smoothing device was used downstream from the sample cell to efficiently eliminate the short-term variation of the signal and remove the mercury from the background and sample aerosol particles (Hu et al . 2015). The Neptune Plus was equipped with nine Faraday cups fitted with 10 11 Ω resistors. Isotopes 142 Nd, 143 Nd, 144 Nd, 145 Nd, 146 Nd, 147 Sm, 148 Nd and 149 Sm were collected in Faraday cups using static mode. The mass discrimination factor for 143 Nd/ 144 Nd was determined using 146 Nd/ 144 Nd (0.7219) with the exponential law. The 149 Sm signal was used to correct the remaining 144 Sm interference on 144 Nd, using the 144 Sm/ 149 Sm ratio of 0.2301. The mass fractionation of 14 7 Sm/ 149 Sm was corrected by the 147 Sm/ 149 Sm normalization, using the 14 7 Sm/ 149 Sm ratio of 1.08680 and exponential law. All data reduction for the MC-ICP-MS analysis of Nd isotope ratios was conducted using “Iso-Compass” software (Zhang et al. 2020).Two natural apatite megacrysts, Durango and MAD, were used as the unknown samples to verify the accuracy of the calibration method for in situ Nd isotope analysis of apatites. The chemical and Nd isotopic compositions of Durango and MAD have been reported by Xu et al . (2015).
Two natural titanite megacrysts, MKED1 and SP-Ttn-01, were used as the unknown samples to verify the accuracy of the calibration method for in situ Nd isotope analysis of titanite. The chemical and Nd isotopic compositions of MKED1 have been reported by Spandler et al. (2016).
One natural monazite megacrysts GBW44069 and another natural titanite megacrysts MKED1 were used as the unknown samples to verify the accuracy of the calibration method for in situ Nd isotope analysis of monazite. The chemical and Nd isotopic compositions of GBW44069 have been reported by Xu et al . (2015).
References
Xu, L. , Hu, Z.C, Zhang, W., Yang, L., Liu, Y.S., Gao, S., In situ Nd isotope analyses in geological materials with signal enhancement and non-linear mass dependent fractionation reduction using laser ablation MC-ICP-MS. Journal of Analytical Atomic Spectrometry , 2015, 30(1), 232-244.
Hu, Z.C., Zhang, W., Liu, Y.S., Gao, S., Li, M., Zong, K.Q., Chen, H.H., Hu, S.H., 2015. “Wave” signal-smoothing and mercury-removing device for laser ablation quadrupole and multiple collector ICPMS analysis: application to lead isotope analysis. Analytical Chemistry, 87(2), 1152–1157.
Carl Spandler,Johannes Hammerli. MKED1:A new titanite standard for in situ analysis of Sm-Nd isotopes and U-Pb geochronology[J].Chemical Geology,2016,425(1):110-126.
Zhang W., Hu Z.C., Liu Y.S. (2020). Iso-Compass: new freeware software for isotopic data reduction of LA-MC-ICP-MS. J. Anal. At. Spectrom., 2020, 35, 1087–1096.
