Rare Earth Elements concentrations 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 from January 14th to March 5th 2017 (IN2017_V01; (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), 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). Sample residues 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.A 400 μL aliquot was removed from the 4 mL digest solution and diluted ~2500 times in 1% HNO3 for rare earth elements (REE) analysis by Sector Field Inductively Coupled Mass Spectrometry (SF-ICP-MS, Thermo Fisher Scientific, Bremen, Germany) at the Central Science Laboratory (UTAS, Hobart, Australia). Element quantification was performed via external calibration using multi-element calibration solutions (MISA-5, QCD Analysts, Spring Lake, NJ, USA). Samples were introduced to the instrument using an Aridius® II desolvating nebulizer (CETAC Technologies, USA). The DSN was tuned daily, and oxide formation for a range of test analytes (Ba, Ce, U etc) was always less than 0.05%. Isotopes 137Ba, 139La, 140Ce, 141Pr, 146Nd, 150Nd, 147Sm, 153Eu, 158Gd, 159Tb, 163Dy, 165Ho, 166Eu, 169Tm, 172Yb and 175Lu were monitored in low resolution mode. Raw intensities were blank and dilution corrected. References- Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report. ANU Research Publications- Huang, H., Gutjahr, M., Kuhn, G., Hathorne, E. C., and Eisenhauer, A. (2021). Efficient Extraction of Past Seawater Pb and Nd Isotope Signatures From Southern Ocean Sediments. Geochemistry, Geophysics, Geosystems, 22(3), 1–22. - Wilson, D. J., Bertram, R. A., Needham, E. F., van de Flierdt, T., Welsh, K. J., McKay, R. M., … Escutia, C. (2018). Ice loss from the East Antarctic Ice Sheet during late Pleistocene interglacials. Nature, 561(7723), 383.

2017年1月14日至3月5日，科研人员在澳大利亚海洋国家设施“调查者”号科考船（R/V Investigator）上，于东南极大陆边缘采集了沉积物岩心（航次编号IN2017_V01；Armand等，2018）。此次名为“萨布丽娜海底调查”的海洋地球科学考察，重点研究托滕冰川与南大洋在多冰川旋回中的相互作用。岩心通过多管取样器（MC）采集，每厘米切片后用塑料袋封装，冷藏保存。

返回母实验室（澳大利亚塔斯马尼亚大学海洋与南极研究所，霍巴特）后，沉积物样品于40℃烘箱中干燥。取300 mg干燥沉积物，加入12 mL pH4的还原溶液（0.005M盐酸羟胺（HH）/1.5%乙酸（AA）/0.001M乙二胺四乙酸钠/0.033M氢氧化钠），涡旋振荡10秒。随后用15 mL 0.02M HH与25% AA混合溶液二次浸取（以去除所有氧化物和过量矿物，分离碎屑组分），并通过旋转装置（20 rpm）振荡过夜。样品经离心分离后，用超纯水冲洗3次，于50℃烘箱中干燥。

取约50 mg干燥碎屑沉积物研磨后，装入聚四氟乙烯瓶，用强酸混合液消解：首先用浓硝酸与30%过氧化氢（1:1）氧化；随后在敞口瓶中加入10 mL硝酸、4 mL盐酸和2 mL氢氟酸，180℃消解至近干；消解残渣转为硝酸形态后，用1 mL硝酸与1 mL高氯酸混合液220℃氧化至完全干燥；最终重新溶解于4 mL 7.5M硝酸中。

从4 mL消解液中取400 μL等分试样，用1%硝酸稀释约2500倍，送至澳大利亚塔斯马尼亚大学中央科学实验室，采用扇形场电感耦合等离子体质谱仪（SF-ICP-MS，德国不来梅赛默飞世尔科技）进行稀土元素（REE）分析。元素定量通过多元素校准溶液（MISA-5，美国新泽西州斯普林莱克QCD分析公司）外部校准实现，样品经美国CETAC技术公司Aridius® II脱溶剂雾化器引入仪器。脱溶剂雾化器每日调谐，钡、铈、铀等测试分析物的氧化物形成率始终低于0.05%。低分辨率模式下监测同位素137Ba、139La、140Ce、141Pr、146Nd、150Nd、147Sm、153Eu、158Gd、159Tb、163Dy、165Ho、166Er、169Tm、172Yb和175Lu，原始强度经空白和稀释校正。

参考文献
-Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). 托滕冰川与南大洋在多冰川旋回中的相互作用（IN2017-V01）：航次后报告. 澳大利亚国立大学研究出版物
-Huang, H., Gutjahr, M., Kuhn, G., Hathorne, E. C., and Eisenhauer, A. (2021). 从南大洋沉积物中高效提取古海水铅和钕同位素信号. 《地球化学、地球物理学、地球系统科学》, 22(3), 1–22.
-Wilson, D. J., Bertram, R. A., Needham, E. F., van de Flierdt, T., Welsh, K. J., McKay, R. M., … Escutia, C. (2018). 晚更新世间冰期东 Antarctic冰盖的冰量损失. 《自然》, 561(7723), 383.