Neodymium isotopic compositions measured in detrital sediment samples collected during the IN2017-V01 voyage of the RV Investigator

Sediment cores were collected from the East Antarctic margin, aboard the Australian Marine National Facility R/V Investigator, during the IN2017_V01 voyage from January 14th to March 5th 2017 (Armand et al., 2018). This marine geoscience expedition, named the “Sabrina Sea Floor Survey”, focused notably on studying the interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles. The cores were collected using a multi-corer (MC), were sliced every centimetre, wrapped up in plastic bags, and stored in the fridge. Back at the home laboratory (IMAS, UTAS, Hobart, Australia), sediment samples were dried in an oven at 40°C. Three hundred mg of dry sediment was then homogenised and vortexed for 10-sec with 12 mL of a reductive solution of 0.005M hydroxylamine hydrochloride (HH) / 1.5% Acetic Acid (AA) / 0.001M Na-EDTA / 0.033M NaOH, at pH 4 (Huang et al., 2021). The sediment was then leached a second time (to ensure the removal of all oxides and excess minerals, i.e. to isolate the detrital fraction) with 15 mL of 0.02M HH, 25% AA solution and agitated using a rotisserie (20 rpm) overnight (Wilson et al., 2018). Samples were then centrifuged, rinsed with Milli-Q water 3 times, and dried in an oven at 50°C. About 50 mg of resulting dry (detrital) sediment was ground, weighed into a Teflon vial, and digested with a strong acid mixture.First, the sediment was oxidized with a mixture of concentrated HNO3 and 30% H2O2 (1:1). Samples were then digested in open vials using 10 mL HNO3, 4 mL HCl, and 2 mL HF, at 180°C until close to dryness. Digested residues were converted to nitric form before being oxidised with a mixture of 1 mL HNO3 and 1 mL HClO4 at 220°C until fully desiccated. Samples were finally re-dissolved in 4 mL 7.5 M HNO3. The digest solution was taken to dryness, oxidized, and converted to 3M HNO3 – 2.5M HCl (3:1) form in preparation for Nd purification using column chemistry. Rare Earth Elements were separated using cation-exchange chromatography (Struve et al., 2016) and Nd isotopes were finally isolated using LN-Spec column chemistry (Pin and Zalduegui, 1997).Purified sample Nd concentrations were checked prior to isotopic analysis using Sector Field Inductively Coupled Mass Spectrometry (ICP-MS) at the Central Science Laboratory (UTAS, Hobart, Australia). Nd isotope ratio measurements were then carried out at the Geochemistry Laboratory of the School of Geography, Environment and Earth Sciences of Victoria University of Wellington, New Zealand, using a Thermo Finnigan Triton thermal ionization mass spectrometer (TIMS). Data were reduced offline for outlier rejection and corrected using 146Nd/144Nd = 0.7219 for mass fractionation using the exponential law, and 144Sm/147Sm = 0.20667 for the Sm interference correction on mass 144. JNdi standard data produced for two load sizes using two amplifier configurations were identical: 143Nd/144Nd = 0.512110 ± 24 2sd (46 ppm 2rsd, n = 16) for 1 ng loads using 10^13Ω amplifiers, vs. 143Nd/144Nd = 0.512112 ± 3 2sd (6 ppm 2rsd, n = 6) for 100 ng loads using 10^11Ω amplifiers. The corrected 143Nd/144Nd were normalised to the JNdi standard with the published value of 0.512115 (Tanaka et al., 2000). Nd isotopic compositions are reported as ɛNd = [(143Nd/144Nd)sample / (143Nd/144Nd)CHUR - 1]x10,000 , where CHUR is the Chondritic Uniform Reservoir with 143Nd/144Nd)CHUR = 0.512638 (Jacobsen and Wasserburg, 1980).References- Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). 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