Critical evaluation of current cleaning protocols for foraminiferal trace metal analyses using single shell Laser-Ablation -ICP measurements
Abstract
Trace element compositions of foraminiferal calcite have been widely used as proxies for past ocean conditions. However, it has been shown that the presence of detrital material, particulate organic matter and diagenically-precipitated overgrowth on test surfaces significantly limit the accuracy of trace element analyses. A number of cleaning methods had been proposed to remove impurities from foraminiferal calcite but their relative effectiveness for foraminiferal trace metal analyses is still debatable. In this work, we employed the microanalytical technique Laser Ablation ICP-MS to compare the most commonly-used cleaning protocols. Distribution of Ca, Mg, Mn, Zn, Ba, Sr, Li, B, Fe, Al across tests of Orbulina universa from modern and Holocene sediments were analysed before and after each cleaning step. The use of Laser Ablation ICP-MS provides accurate and direct comparison of the effectiveness of each cleaning protocol, which was applied to fragments of a single foraminifera test. We also present results obtained using a novel automated cleaning device, "fOraccle", for cleaning single shell and bulk foraminiferal samples. This instrument minimises manual handling of chemical reagents during cleaning, thereby improving reproducibility of the Me/Ca measurements. Based on these results, we will discuss the composition of surface contamination on foraminiferal tests as well as possible ways to improve current cleaning protocols.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B21C0367S
- Keywords:
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- 1050 GEOCHEMISTRY / Marine geochemistry;
- 1065 GEOCHEMISTRY / Major and trace element geochemistry;
- 4924 PALEOCEANOGRAPHY / Geochemical tracers;
- 4994 PALEOCEANOGRAPHY / Instruments and techniques