Whole rock geochemistry - radiogenic isotopes - from selected basalts dredged from seamounts in the south Tasman Sea during RV Investigator voyage IN2018_V08

Sr-Nd-Pb-Hf isotope analytical techniqueSplits of agate-milled powders (100-140 mg) were leached with 6M HCl (100oC, 60 min) and digested at high pressure (HF, 160oC, 48 hrs; HCl, 160oC, 12 hrs). Replicate splits were processed for three samples. Pb was extracted on small columns of AG1-X8 (100-200) anion exchange, using the HBr-HCl technique. Hf, Nd, and Sr were extracted using Eichrom LN-, TRU/LN, and Sr resin, respectively (Münker et al., 2001; Pin et al., 2014). Total analytical blanks (~50 pg for Pb and Hf; ≤100 pg for Nd and Sr) are negligible compared to the amounts of Pb, Hf, Nd, and Sr processed. All isotopic analyses were carried out on a Nu Plasma multi-collector ICP-MS with sample introduction via a low-uptake Glass Expansion PFA nebuliser and a CETAC Aridus desolvator. Sensitivity in this set-up is in the range of 130-150 V/ppm Sr, Nd, Pb, or Hf. Instrumental mass bias in Nd, Sr, and Hf analyses was corrected by normalizing to 146Nd/144Nd = 0.7219, 86Sr/88Sr = 0.1194, and 179Hf/177Hf=0.7325, respectively, using the exponential law. 143Nd/144Nd, 87Sr/86Sr, and 176Hf/177Hf are reported relative to La Jolla Nd = 0.511860, SRM987 = 0.710230, and JMC475 = 0.282160. Results for USGS rock and other standards are consistent with TIMS and MC-ICP-MS reference values (see http://dx.doi.org/doi:10.26179/04ec-cc75 for further details). Typical in-run precisions (2sd) 4 are ±0.000010 (Nd), ±0.000016 (Sr), and ±0.000008 (Hf). External (2sd) precisions are ±0.000020, ±0.000040, and ±0.000015, respectively. Mass bias for Pb was corrected using the thallium-doping technique (Woodhead, 2002). This produces data with an external precision (2sd) of ±0.04-0.06% for 206Pb/204Pb and 207Pb/204Pb, and 0.07-0.09% for 208Pb/204Pb.