Neodymium isotope analyses after combined extraction of actinide and lanthanide elements from seawater and deep‐sea coral aragonite

Abstract

Isotopes of the actinide elements protactinium (Pa), thorium (Th), and uranium (U), and the lanthanide element neodymium (Nd) are often used as complementary tracers of modern and past oceanic processes. The extraction of such elements from low abundance matrices, such as seawater and carbonate, is however labor‐intensive and requires significant amounts of sample material. We here present a combined method for the extraction of Pa, Th, and Nd from 5 to 10 L seawater samples, and of U, Th, and Nd from <1 g carbonate samples. Neodymium is collected in the respective wash fractions of Pa‐Th and U‐Th anion exchange chromatographies. Regardless of the original sample matrix, Nd is extracted during a two‐stage ion chromatography, followed by thermal ionization mass spectrometry (TIMS) analysis as NdO+. Using this combined procedure, we obtained results for Nd isotopic compositions on two GEOTRACES consensus samples from Bermuda Atlantic Time Series (BATS), which are within error identical to results for separately sampled and processed dedicated Nd samples (εNd = −9.20 ± 0.21 and −13.11 ± 0.21 for 15 and 2000 m water depths, respectively; intercalibration results from 14 laboratories: εNd = −9.19 ± 0.57 and −13.14 ± 0.57). Furthermore, Nd isotope results for an in‐house coral reference material are identical within analytical uncertainty for dedicated Nd chemistry and after collection of Nd from U‐Th anion exchange chromatography. Our procedure does not require major adaptations to independently used ion exchange chromatographies for U‐Pa‐Th and Nd, and can hence be readily implemented for a wide range of applications.

A geochemical approach to reconstruct modern dust fluxes and sources to the South Pacific

“…The remaining solution was then passed through a two-stage HBr-HNO 3 -based Pb extraction using 100 mL AG1-X8 (100-200 mm mesh) resin (after Lugmair and Galer, 1992). The alkaline earth metals including Sr were separated from the REE using a HClbased procedure with Biorad Ò AG50W-X8 (200-400 mm mesh) resin (Strelow, 1960;Struve et al, 2016). Strontium was isolated from the remaining sample matrix using Tris-Kem Sr spec Ò resin (Horwitz et al, 1992) and Nd was separated from the REE using TrisKem LnSpec Ò chemistry (Pin and Zalduegui, 1997).…”

Isotopic analysis of sub‐nanogram neodymium loads using new ATONA™ amplifiers

“…For this study 100‐pg loads of JNdi‐1 were chosen because this has become a benchmark within the geochemistry community for testing the reproducibility of the analysis of small Nd samples by TIMS. The 100‐pg level is significant because procedural blanks for rock samples processed through Nd separation chemistry are frequently in the 1 to 5 pg range for laboratories with very low‐background Nd separation chemistry 22–24 . Therefore, a sample with 100 pg of Nd contributes 20 to 100 times more Nd than the Nd contribution from the process blank, allowing for the accurate measurement of 143 Nd/ 144 Nd in a sample without significant contribution from the process blank.…”

“…The 100-pg level is significant because procedural blanks for rock samples processed through Nd separation chemistry are frequently in the 1 to 5 pg range for laboratories with very low-background Nd separation chemistry. [22][23][24] Therefore, a sample with 100 pg of Nd contributes 20 to 100 times more Nd than the Nd contribution from the process blank, allowing for the accurate The filament, with loaded sample and slurry, was maintained at 0.8 A for at least 10 min to dry. Once dry, the filament current was set to 1.8 A until all the parafilm was burned from the filament.…”

New Perspectives on the 143Nd/144Nd Palaeoceanographic Tracer on Foraminifera: The State‐of‐the‐Art Frontiers of Analytical Methods

“…The paraffin film was glued at 3.0 A onto the tungsten filament leaving a 2 mm gap. The Ta–HF activator (Struve et al., 2016) and the sample aliquot were loaded in a sandwich style. The current was set at 2.0 A and the activator (0.5 μl) was loaded first and evaporated to near dryness, followed by a similar loading of the sample in 0.5 μl droplets, and finished by another layer of the activator (0.5 μl).…”

“…has been well known that TIMS measurements of Nd isotopic composition in the form of NdO + can potentially lead to high-precision 143 Nd/ 144 Nd determinations of low Nd loads due to much higher ion efficiency (∼10% or even higher;Harvey & Baxter, 2009;Struve et al, 2016) when compared to the widely used double filament configuration (∼1%). On the other hand, the NdO + method requires sufficient separation of Nd from other LREE (La, Ce, and Pr) during ion exchange chemistry as different oxygen species of these elements directly interfere with the determined Nd masses (e.g.,141 Pr 18 O + on 143 Nd 16 O + etc.…”