Accurate trace element analysis of speleothems and biogenic calcium carbonates by LA-ICP-MS

Klaus Peter Jochum*, Denis Scholz, Brigitte Stoll, Ulrike Weis, Stephen A. Wilson, Qichao Yang, Antje Schwalb, Nicole Börner, Dorrit E. Jacob, Meinrat O. Andreae

*Corresponding author for this work

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Abstract

The high spatial resolution of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) microanalysis of speleothems and biogenic calcium carbonates makes it possible to improve our understanding of past climatic conditions. However, there are analytical problems associated with this method, such as molecular interferences, elemental fractionation, and mass-load-dependent matrix effects, when using NIST silicate reference glasses for calibration.Our study with a sector-field ICP-MS shows that many masses are affected by interferences, such as 24Mg + by 48Ca ++ or 31P + by 15N 16O +. Elemental fractionation and mass-load-dependent matrix effects have been detected for both 213 and 193nm Nd:YAG lasers. They are small for refractory lithophile elements, in particular for the 193nm laser (<5%). For chalcophile/siderophile trace elements with low boiling points, however, these effects are large (up to 40% and 20% for the 213 and 193nm lasers, respectively), and variable for the NIST glasses and carbonates.In this paper, a protocol for precise and accurate LA-ICP-MS analysis of calcium carbonates is established. Isotopes for interference-free measurements at low (M/δM ~. 300) and medium (M/δM ~. 4000) mass resolution have been identified. The NIST glasses are suitable for calibration of refractory lithophile element concentrations. However, matrix-matched calibration with carbonate reference materials, such as USGS MACS-1 or MACS-3, is necessary for accurate analysis of chalcophile/siderophile elements with low boiling points. Analytical reproducibility (RSD) is a factor of ~. 2 better using the 193. nm laser than the 213. nm laser. As shown by the analysis of MACS-1 and MACS-3, LA-ICP-MS analyses yield results that agree with the reference values within relative uncertainties of ca. 5-10% at the 95% confidence level.We have applied LA-ICP-MS for the determination of trace element concentrations in calcite and aragonite layers of a stalagmite and found large variations for Mg, Zn, Sr, and U. In ostracod shells, the concentrations of some trace elements (. e.g., Sr and Ba) vary significantly, indicating the potential for paleoclimate research.

Original languageEnglish
Pages (from-to)31-44
Number of pages14
JournalChemical Geology
Volume318-319
DOIs
Publication statusPublished - 15 Jul 2012
Externally publishedYes

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    Jochum, K. P., Scholz, D., Stoll, B., Weis, U., Wilson, S. A., Yang, Q., ... Andreae, M. O. (2012). Accurate trace element analysis of speleothems and biogenic calcium carbonates by LA-ICP-MS. Chemical Geology, 318-319, 31-44. https://doi.org/10.1016/j.chemgeo.2012.05.009