微區原位硫化物硫同位素比值測試在武漢上譜分析科技有限責任公司利用激光剝蝕多接收杯電感耦合等離子體質譜（LA-MC-ICP-MS）完成。激光剝蝕系統為Geolas HD（Coherent，德國），MC-ICP-MS為Neptune Plus（Thermo Fisher Scientific，德國）。激光剝蝕系統使用氦氣作為載氣。分析采用單點模式，為了解決分析過程中硫同位素比值的Down Hole分餾效應（Fu et al. 2016），選擇采用大束斑（44微米）和低頻率（2Hz）的激光條件，單次分析約剝蝕100個激光脈沖。同時配備了信號平滑裝置（Hu et al. 2015），確保在低頻率條件下獲得穩定的信號。激光能量密度固定5.0 J/cm2。質譜儀Neptune Plus配備9個法拉第杯和1011歐姆電阻放大器，采用L3，C和H3三個法拉第杯同時靜態接收32S，33S和 34S信號。高性能的Jet+X錐組合被采用提高信號強度。氮氣（4 ml/min）被引入等離子體降低多原子離子干擾。中分辨模式（約5000）被采用。 硫同位素質量分餾采用SSB方法校正。為避免基體效應，黃鐵礦、磁黃鐵礦、鎳黃鐵礦等樣品采用黃鐵礦參考物質PPP-1校正。黃銅礦樣品采用國家黃銅礦標準物質GBW07268的粉末壓片校正。硫化銀樣品采用國際硫化銀標準物質IAEA-S-1的粉末壓片校正。以上樣品δ34Sv-CDT推薦值請參考Fu et al.（2016）。測試過程中，實驗室內部磁黃鐵礦參考物質SP-Po-01（δ34Sv-CDT=1.4±0.4），黃銅礦參考物質SP-CP-01（δ34Sv-CDT=5.5±0.3）和國際硫化銀標準物質IAEA-S-2（δ34Sv-CDT=22.58±0.39）和IAEA-S-3（δ34Sv-CDT=-32.18±0.45）作為質量監控樣品被重復分析，驗證實驗方法的準確性。詳細的儀器操作條件和分析測試方法可以參考Fu et al.（2016）。全部分析數據采用專業同位素數據處理軟件“Iso-Compass”進行數據處理（Zhang et al., 2020)。
22.2 In-situ S isotope analysis of sulfide by using LA-MC-ICP-MS
In situ sulfur isotope analyses of sulfide were 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 for the ablation cell and was mixed with argon (makeup gas) after the ablation cell. The single spot ablation mode was used. Then the large spot size (44 μm) and slow pulse frequency (2 Hz) were used to avoid the down hole fractionation effect which have been reported by Fu et al. (2016). 100 laser pulses were completed in one analysis. A new signal-smoothing device was used downstream from the sample cell to efficiently eliminate the short-term variation of the signal, especially for the slow pulse frequency condition (Hu et al. 2015). The laser fluence was kept constant at ~5 J/cm2. The Neptune Plus was equipped with nine Faraday cups fitted with 1011Ω resistors. Isotopes 32S, 33S and 34S were collected in Faraday cups using static mode. The newly designed X skimmer cone and Jet sample cone in Neptune Plus were used to improve the signal intensity. The nitrogen (4 ml/min) was added to the central gas flow to reduce the polyatomic interferences. All measurements were performed using the medium-resolution with a revolving power (as defined by a peak edge width from 5-95% of the full peak height) that was always greater than 5000. A standard-sample bracketing method (SSB) was employed to correct for instrumental mass fractionation. To avoid the matrix effect, a pyrite standard PPP-1, a chalcopyrite standard GBW07268 (a pressed pellet) and a synthetic Ag2S standard IAEA-S-1 (a pressed pellet) were chosen as reference materials for correcting the natural pyrite, pyrrhotite and pentlandite samples, the natural chalcopyrite samples and the natural Ag2S samples, respectively. The reference values of δ34Sv-CDT in these standards have been reported by Fu et al. (2016). In addition, the in-house references of a pyrrhotite SP-Po-01 (δ34Sv-CDT=1.4±0.4), a chalcopyrite SP-CP-01 (δ34Sv-CDT=5.45±0.3) and two synthetic Ag2S standard IAEA-S-2 (δ34Sv-CDT=22.58±0.39) and IAEA-S-3 (δ34Sv-CDT=-32.18±0.45) were analyzing repeatedly as unknown samples to verify the accuracy of the calibration method. The more detail of the in situ Pb isotopic ratios analysis was described in Fu et al. (2016). All data reduction for the MC-ICP-MS analysis of S isotope ratios was conducted using “Iso-Compass” software (Zhang et al. 2020). References Fu, J., Hu, Z.C., Zhang, W., Yang, L., Liu, Y., Li, M., et al., 2016. In situ, sulfur isotopes (δ34S and δ33S) analyses in sulfides and elemental sulfur using high sensitivity cones combined with the addition of nitrogen by Laser Ablation MC-ICP-MS. Analytica Chimica Acta, 911, 14-26. 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. 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.