Th and U isotopes concentrations measured in 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) and a Kasten corer (KC). The MC were sliced every centimetre, wrapped up in plastic bags, and stored in the fridge. The KC was sub-sampled using a u-channel; and sliced every centimetre once back the home laboratory (IMAS, UTAS, Hobart, Australia).

About 200 mg of dried and ground sediment were weighed into a clean Teflon vial and oxidized with a mixture of concentrated HNO3 and 30% H2O2 (1:1). The resulting solutions were gravimetrically spiked with ~ 24 pg of 229Th (NIST 4328C, National Institute of Standards and Technology, USA) and ~ 2 ng of 236U (IRMM-3660a, Institute for Reference Materials and Measurements, European Union) and left to equilibrate overnight. Samples were then digested in open vials using an acid mixture comprising 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.

Thorium and uranium were isolated from the sediment digest using AG1-X8 anion exchange resin (Bio-Rad, USA), following the procedure described in Negre et al., (2009). Prior to analysis, purified samples were filtered using Pall® Acrodisc® ion chromatography syringes and 0.45 μm filters (Sigma-Alderich®, USA). 229Th, 230Th, 234U and 235U were analysed by Sector Field Inductively Coupled Mass Spectrometry (SF-ICP-MS, Thermo Fisher Scientific, Bremen, Germany) at the Central Science Laboratory (UTAS, Hobart, Australia). Samples were introduced in the ICP using an Aridius® II desolvating nebulizer (DSN, CETAC Technologies, USA) and with the capacitive guard electrode turned on to limit the oxide formation and to enhance sensitivity. Samples were analysed in batches of three and bracketed by a natural uranium standard (Certified Reference Material CRM 145, New Brunswick Laboratory, USA) and two acid blanks (2% HNO3, 0.1% HF). The sample introduction system was rinsed for 5 minutes between each sample with a matching 2% HNO3 and 0.1% HF solution.

The raw intensities of 230Th and 234U were corrected for procedural blank, tailing and mass bias (Anderson et al., 2012; Shen et al., 2002). The intensity of 230Th was corrected from the tailing of 232Th using the log mean intensities of the half masses 229.5 and 230.5. The mass bias was determined by the measurements of the 235U/234U ratio of the CRM-145. Concentrations were calculated using isotope dilution equations (Sargent et al., 2002).

References

- Anderson, R. F., Fleisher, M. Q., Robinson, L. F., Edwards, R. L., Hoff, J. A., Moran, S. B., … Francois, R. (2012). GEOTRACES intercalibration of 230Th, 232Th, 231Pa, and prospects for 10Be. Limnology and Oceanography: Methods, 10(4), 179–213. https://doi.org/10.4319/lom.2012.10.179

- 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, (March). https://doi.org/http://dx.doi.org/10.4225/13/5acea64c48693

- Negre, C., Thomas, A. L., Mas, J. L., Garcia-orellana, J., Henderson, G. M., Masque, P., and Zahn, R. (2009). Separation and Measurement of Pa , Th , and U Isotopes in Marine Sediments by Microwave-Assisted Digestion and Multiple Collector Inductively Coupled Plasma Mass. Analytical Chemistry, 81(5), 1914–1919. https://doi.org/10.1126/science.276.5313.782.(3)

- Sargent, M., Harrington, C., and Harte, R. (2002). Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS). Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS). Royal Society of Chemistry. https://doi.org/10.1039/9781847559302-00001

- Shen, C.-C., Lawrence Edwards, R., Cheng, H., Dorale, J. A., Thomas, R. B., Bradley Moran, S., … Edmonds, H. N. (2002). Uranium and thorium isotopic and concentration measurements by magnetic sector inductively coupled plasma mass spectrometry. Chemical Geology, 185(3–4), 165–178. https://doi.org/10.1016/S0009-2541(01)00404-1

Identification info

Alternate title: Th and U isotopes concentrations measured in sediment samples collected during the IN2017-V01 voyage of the RV Investigator

Date (Publication): 2023-04-03

Edition: 1

Citation identifier

Dataset DOI

Title: Information and documentation - Digital object identifier system

Date (Publication): 2012-04-23

Citation identifier: ISO 26324:2012

Citation identifier: doi:10.26179/6mh1-5244

Originator

Creac'h, L., Noble, T. and Townsend, A.

Publisher

Australian Antarctic Data Centre

Principal investigator

CREAC'H, LAYLA

Institute for Marine and Antarctic Studies

20 Castray Esplanade, Battery Point

Hobart

TAS

7004

Australia

Principal investigator

NOBLE, TARYN

Institute for Marine and Antarctic Studies

20 Castray Esplanade, Battery Point

Hobart

TAS

7004

Australia

Collaborator

CREAC'H, LAYLA

Institute for Marine and Antarctic Studies

20 Castray Esplanade, Battery Point

Hobart

TAS

7004

Australia

Collaborator

TOWNSEND, ASHLEY

Central Science Laboratory, Hobart Campus, Chemistry Building

Private Bag 74

Hobart

TAS

7001

Australia

Name: CAASM Metadata

Other citation details: Unreleased data

Website: https://data.aad.gov.au/metadata/records/AAS_4419_Th_U_isotopes_sediment

Purpose: These data were collected to determine radioactive isotopes concentrations in the sediment, and to determine vertical particle fluxes for palaeoceanographic reconstructions.

Status: Completed

Custodian

AU/AADC > Australian Antarctic Data Centre, Australia - AADC, DATA OFFICER (DATA CENTER CONTACT)

Australian Antarctic Division

203 Channel Highway

Kingston

Tasmania

7050

Australia

+61 3 6232 3244

+61 3 6232 3351 (facsimile)

Topic category

Oceans

Extent