Data Quality

a. Fluence Assessment

b. Determining for Primary Calibration Standard

• To determine the optimal primary calibration standard for my LA-ICP-MS analyses, I evaluated four candidates: NIST 610, NIST 612, BHVO, and GSC. Each candidate was tested as the primary calibration standard by generating calibration curves and using these to calculate the elemental concentrations in the remaining three standards, which served as external reference standards. The recovery values, expressed as the ratio of measured to reference concentrations, were calculated for each element in each external standard, providing insight into the accuracy of the calibration. 
• A table summarizing these results includes the recovery values for each element across all standards, as well as the grand average recovery for each primary standard (last row). 
• GSC was ultimately selected as the primary calibration standard because it yielded grand average recoveries closest to 1.0 across all three external reference standards, indicating superior accuracy and consistency in reproducing certified values. This choice was applied to both olivine grains and serpentine veins, ensuring robust and reliable calibration for subsequent analyses.

Olivine Recovery Table

Serpentine Recovery Table

c. Signal Intensity Assessment

• Measured intensities were converted to elemental concentrations (ppm) using Iolite software (Paton et al., 2011), using 24Mg as the internal standard and a Mg index concentration value of 29.8 wt% for San Carlos olivine with a FO# = 90.
• Limits of detections for all isotopes were calculated using mechanics of the Longerich et al. (1997) study. 
• For olivine, typical concentrations were 1 to 10s times higher than limits of detection for Al, P, Ca, Sc, Ti, V, Cr, and Zn. Typical concentrations were 1000s to 100000s times higher than limits of detection for Mg, Si, Mn, Fe, Co, and Ni. Na, K, Sr, Zr, La, Ce, Nd, Sm, and Hf concentrations were mainly below detection, and are not subsequently considered. For serpentine veins, typical concentrations were 1 to 10s times higher than limits of detection for Na, Al, K, Ca, Sc, Ti, V, Cr, and Zn. Typical concentrations were 100s to 10000s times higher than limits of detection for Mg, Si, Mn, Fe, Co, Ni, and Sr. P, Zr, La, Ce, Nd, Sm, and Hf concentrations were mainly below detection, and are not subsequently considered.
• Median concentrations were chosen over the means of the isotope measurements to eliminate the effect of outliers likely representing non-olivine concentrations. They are most likely pyroxenes due to their abnormally high Al concentrations.

Olivine Intensity Assessment

Serpentine Intensity Assessment

d. Isotopic Concentrations Comparison Between Olivine and Serpentine

The major (Mg, Fe, Si) and minor (Ca, Ni) elements in the olivine grains generally remain unchanged after serpentinization. In comparison, most of the trace elements become enriched in the serpentine veins.