Thermal ionisation mass spectrometry (TIMS): Rock reference material BCR-2 was processed with every batch of chemistry and yielded JNdi-1 normalized 143Nd/144Nd ratios of 0.512637 ± 0.000011 (2SD, n = 32) on loads of 10 and 30 ng Nd, identical to 143Nd/144Nd = 0.512637 ± 0.000006 published by Weis et al. (2006). A similar precision was obtained from replicate analyses of 10 and 30 ng Nd loads of our in-house coral reference material (143Nd/144Nd = 0.512336 ± 0.000009, 2SD, n = 23; cf. Crocket et al., 2014). We report the higher 2SD uncertainty from repeat BCR-2 analyses as 2SD for coral samples, except where the within-run 2SE was higher than the 2SD of BCR-2 repeat analyses, in which case the propagated error is reported. Full procedural blanks of combined U, Th, and Nd separation from aragonitic matrix ranged from 2 to 27 pg Nd (n = 20), of which the Nd chemistry blank contributed from 1 to 17 pg (n = 10), which are minimal (see also Struve et al., 2017).

Multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS): The reported external reproducibility on samples was estimated from the within-session 2SD on JNdi-1 Nd isotope standards. Accompanying analyses (also at 10 - 20 ppb) of BCR-2 rock reference material gave 143Nd/144Nd = 0.512641 ± 0.000013 (2SD, n = 11) and our in-house coral reference material yielded 143Nd/144Nd = 0.512337 ± 0.000013 (2SD, n = 5), both indicating long term reproducibility in excellent agreement with the TIMS values. Full procedural blanks of MC-ICP-MS samples including combined U, Th, and Nd separation ranged from 3 to 16 pg Nd (n = 5), while Nd chemistry blanks ranged from 1 to 10 pg (n = 5), which are minimal.

References:

Crocket, K.C., Lambelet, M., van de Flierdt, T., Rehkamper, M., Robinson, L.F., 2014. Measurement of fossil deep-sea coral Nd isotopic compositions and concentrations by TIMS as NdO+, with evaluation of cleaning protocols. Chemical Geology 374-375, 128-140.

Struve, T., van de Flierdt, T., Burke, A., Robinson, L.F., Hammond, S.J., Crocket, K.C., Bradtmiller, L.I., Auro, M.E., Mohamed, K.J., White, N.J., 2017. Neodymium isotopes and concentrations in aragonitic scleractinian cold-water coral skeletons - Modern calibration and evaluation of palaeo-applications. Chemical Geology 453, 146-168.

Weis, D., Kieffer, B., Maerschalk, C., Barling, J., de Jong, J., Williams, G.A., Hanano, D., Pretorius, W., Mattielli, N., Scoates, J.S., Goolaerts, A., Friedman, R.M., Mahoney, J.B., 2006. High-precision isotopic characterization of USGS reference materials by TIMS and MC-ICP-MS. Geochem. Geophys. Geosyst. 7, doi: 10.1029/2006gc001283.