Analytical Techniques

Researchers around the globe can take advantage of this state-of-the-art facility. In addition to routine analysis, investigators are welcome to develop new analytical techniques within the scope of this facility. We have currently set up the routine isotope ratio measurements of the bulk samples (powder, mineral) for the Sr-Nd-Hf-Pb isotope systems in the Neptune Plus MC-ICPMS and in situ trace element concentration measurements in the laser ablation system coupled with X-series-2 quadrupole ICPMS.

Isotope ratio measurements by Neptune Plus

Repeated measurements of 200 ppb Sr standard NBS SRM 987 yield an average of  87Sr/86Sr = 0.710246 ± 19 (2σ, n=75). Isotopic compositions are measured using an H-sampler cone, an H-skimmer cone, a glass spray chamber, a 50µl PFA nebulizer and by taking a baseline measurement at -0.5 amu. The 87Sr/86Sr ratios are corrected to 88Sr/86Sr  = 0.1194 for instrumental mass fractionation using an exponential law. The accepted value for NBS SRM 87Sr/86Sr = 0.71024. The total procedural blank for Sr is < 50 pg.

NBS-987NBS-987Repeated measurements of 200 ppb Nd standard JNd-i yield an average of 143Nd/144Nd = 0.512093 ± 15 (2σ, n=104). Isotopic compositions are measured using an H-sampler cone, an H-skimmer cone, a glass spray chamber, a 50µl PFA nebulizer and by taking a baseline measurement at -0.5 amu. The 143Nd/144Nd ratios are corrected to 146Nd/144Nd = 0.7219 for instrumental mass fractionation using an exponential law. The accepted value for JNd-i is 143Nd/144Nd= 0.512115. The total procedural blank for Nd is < 30 pg.

JNd-iJNd-i

Repeated measurements of 200 ppb Hf standard JMC-475 yield an average of 176Hf/177Hf = 0.282152 ± 11 (2σ, n=89). Isotopic compositions are measured using an H-sampler cone, an H-skimmer cone, a glass spray chamber and by taking a baseline measurement at -0.5 amu. The 176Hf/177Hf ratios are corrected to 179Hf/177Hf = 0.7325 for instrumental mass fractionation using an exponential law. The accepted value for JMC-475 176Hf/177Hf= 0.282160. The total procedural blank for Hf is < 30 pg.

JMC-475JMC-475

Repeated measurements of 50-100 ppb Pb standard NBS SRM-981 yield an average of 206Pb/204Pb= 16.9329 ± 9, 207Pb/204Pb= 15.4864 ± 9, 208Pb/204Pb = 36.6828 ± 30 (2σ, n=75). Pb standard solution is spiked with NBS SRM-997 Tl solution with a Pb/Tl = 4 to correct for the mass fractionation using exponential law with a 203Tl/205Tl = 0.418922. Isotopic compositions are measured using an H-sampler cone, an H-skimmer cone, a 50µl nebulizer, an APEX introduction system and by taking a baseline measurement at -0.5 amu. The accepted values for NBS SRM-981 is 206Pb/204Pb= 16.9356, 207Pb/204Pb= 15.4891, 208Pb/204Pb= 36.7006 (Todt et al., 1996). The total procedural blank for Pb is < 50 pg.

NBS-981NBS-981

In situ trace element concentration measurements by Laser ablation

Figures below show the results of in situ trace element concentration measurements for USGS glass standards by 193 nm excimer Photon Machines Analyte G2 laser ablation system coupled with Thermo Scientific X-series-2 quadrupole ICPMS. Instrument is tuned with a NIST 612 glass standard to keep the ThO/Th < 1%. Laser is ablated with a spot size of 160 µm, repeat rate of 20 Hz and a fluence of 3.78 J/cm2 at 50% energy. Typical analysis consists of 20-30 sec of gas blank followed by 30-40 sec of sample ablation. Figures below show the  % deviation from the GeoReM (http://georem.mpch-mainz.gwdg.de/) preferred values for the USGS glass standards and reproducibilty as 1 standard deviation (%) for 40 analyses.