微区原位长石，单斜辉石和磷灰石Sr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）。8个法拉第杯（从L4到H3）被同时用于接收Kr，Rb，Er++，Yb++和Sr信号的离子信号。Jet+X锥组合被采用以提高仪器灵敏度。激光剥蚀系统使用氦气作为载气。分析采用单点模式，激光束斑大小根据样品Sr信号强度调节，一般为60-160 μm。激光剥蚀速率为8-15 Hz。激光能量密度固定在~10.0 J/cm2。分析过程配备了信号平滑装置以提高信号稳定性和同位素比值测试精密度（Hu 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）。Sr同位素干扰校正采用Tong et al.（2016）和Zhang et al.（2018）的方法。校正首先扣除气体背景Kr干扰。接下来校正方案为（1）监控167Er++, 173Yb++信号强度，利用Er和Yb天然丰度比值（Berglund and Wieser, 2011），扣除168Er++ 对84Sr，170Er++和170Yb++对85Rb，172Yb++对86Sr，以及174Yb++对87Sr的干扰;（2）监测85Rb信号强度，利用实验获得的经验87Rb/85Rb比值和指数法则，校正87Rb对87Sr的干扰。经验87Rb/85Rb比值通过测定高Rb且已知87Sr/86Sr组成的标准样品获得。Sr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88Sr/86Sr = 8.375209估算获得（Tong et al. 2016, Zhang et al. 2018）。 两个天然长石标样，YG0440（钠长石）和YG4301（钙长石），作为未知样品监控微区原位长石Sr同位素校正方法的可靠性。YG0440和YG4301的化学组成和Sr同位素组成参见Zhang et al.（2018）。 一个天然单斜辉石标样，HNB-8（Sr=89.2 µg g-1），作为未知样品监控微区原位单斜辉石Sr同位素校正方法的可靠性。HNB-8的化学组成和Sr同位素组成参见Tong et al.（2016）。 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Sr同位素校正方法的可靠性。Durango和MAD的化学组成和Sr同位素组成参见Yang et al.（2014）。
20.2 In situ Sr isotope analysis of feldspar, clinopyroxene and apatite by using LA-MC-ICP-MS
Sr isotope ratios of feldspars, clinopyroxenes and apatites were measured by a Neptune Plus MC-ICP-MS (Thermo Fisher Scientific, Bremen, Germany) in combination with a Geolas HD excimer ArF laser ablation system (Coherent, Göttingen, Germany) at the Wuhan Sample Solution Analytical Technology Co., Ltd, Hubei, China. The Neptune Plus was equipped with nine Faraday cups fitted with 1011 Ω resistors. The Faraday collector configuration of the mass system was composed of an array from L4 to H3 to monitor Kr, Rb, Er, Yb and Sr. The combination of the high-sensitivity X-skimmer cone and Jet-sample cone was employed. In the laser ablation system, helium was used as the carrier gas for the ablation cell. For a single laser spot ablation, the spot diameter ranged from 60 to 160 μm dependent on Sr signal intensity. The pulse frequency was from 8 to 15 Hz, but the laser fluence was kept constant at ~10 J/cm2. A new signal smoothing device (Hu et al. 2015) was used downstream from the sample cell to eliminate the short-term variation of the signal. All data reduction for the MC-ICP-MS analysis of Sr isotope ratios was conducted using “Iso-Compass” software (Zhang et al. 2020). The interference correction strategy was the same as the one reported by Tong et al. (2016) ａnd Zhang et al. (2018). Firstly, the regions of integration for both gas background and sample were selected. Following background correction, which removes the background Kr+ signals, no additional Kr peak stripping was applied. Interferences were corrected in the following sequence: (1) the interferences of 168Er++ on 84Sr, 170Er++ ａnd 170Yb++ on 85Rb, 172Yb++ on 86Sr, and 174Yb++ on 87Sr were corrected based on the measured signal intensities of 167Er++, 173Yb++ ａnd the natural isotope ratios of Er and Yb (Berglund and Wieser, 2011); (2) the isobaric interference of 87Rb on 87Sr was corrected by monitoring the 85Rb signal intensity and a user-specified 87Rb/85Rb ratio using an exponential law for mass bias. The user-specified 87Rb/85Rb ratio was calculated by measuring some reference materials with a known 87Sr/86Sr ratio. Following the interference corrections, mass fractionation of Sr isotopes was corrected by assuming 88Sr/86Sr = 8.375209 (Tong et al. 2016 and Zhang et al. 2018) and applying the exponential law. During the LA-MC-ICP-MS analysis, a synthesised clinopyroxene glass (CPX05G, Sr = 518 µg g-1) was used as monitor to verify the accuracy of the calibration method. Two silicate glasses of StHs6/80-G and T1-G (MPI-DING), that both have high concentration of Rb, were used to calculated a specified 87Rb/85Rb ratio for the Rb interference correction. Two natural feldspar megacrysts, YG0440 (albite) and YG4301 (anorthite) were used as the unknown samples to verify the accuracy of the calibration method for in situ Sr isotope analysis of feldspars. The chemical and Sr isotopic compositions of YG0440 and YG4301 have been reported by Zhang et al. (2018). A natural clinopyroxene megacryst (Cpx, HNB-8) with a low Sr concentration (89.2 µg g-1) was analyzed as the unknown sample for in situ Sr isotope analysis of Cpx samples. The chemical and Sr isotopic compositions of HNB-8 have been reported by Tong et al. (2016). Two natural apatites, Durango and MAD were used as the unknown samples for in situ Sr isotope analysis of apatites. The chemical and Sr isotopic compositions of Durango and MAD have been reported by Yang et al. (2014). 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