A Caltech Library Service

Accurate Mg/Ca, Sr/Ca, and Ba/Ca ratio measurements in carbonates by SIMS and NanoSIMS and an assessment of heterogeneity in common calcium carbonate standards

Gabitov, R. I. and Gagnon, A. C. and Guan, Y. and Eiler, J. M. and Adkins, J. F. (2013) Accurate Mg/Ca, Sr/Ca, and Ba/Ca ratio measurements in carbonates by SIMS and NanoSIMS and an assessment of heterogeneity in common calcium carbonate standards. Chemical Geology, 356 . pp. 94-108. ISSN 0009-2541. doi:10.1016/j.chemgeo.2013.07.019.

PDF - Supplemental Material
See Usage Policy.

PDF - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


As archives of past climate variability, the micron and sub-micron scales of element:calcium (Me/Ca) variability in both biogenic and inorganic carbonates contain important geochemical information. Ideally working at smaller and smaller scales leads to higher temporal resolution of past changes, but more often it has revealed the strong overprint of other processes on the climate signal. Therefore, the role of SIMS and NanoSIMS techniques in studying paleoenvironmental proxies continues to increase. We evaluate the accuracy and precision of the CAMECA ims 7F-GEO and NanoSIMS-50L ion probes for measurements of Sr/Ca, Mg/Ca, and Ba/Ca ratios in carbonate minerals. Nine carbonate reference materials were examined for their ^(88)Sr/^(42)Ca, ^(24)Mg/^(42)Ca, and ^(138)Ba/^(42)Ca ratios using a primary O^− beam with spot sizes of 20–40 μm (SIMS) and 0.8–2 μm (NanoSIMS). To assess accuracy, seven of these standards were analyzed for Sr/Ca and Mg/Ca with ID-ICP-MS. Variability in the elemental ratios arising from drift and changes in the tuning of the ims 7F-GEO over a nine month period is smaller than the chemical heterogeneity of the most frequently analyzed standards (OKA and Blue-CC). Across a whole crystal, Blue-CC is more homogeneous (1σ of 2.39% and 1.60% for Sr/Ca and Mg/Ca respectively) than OKA, but in the bulk matrix of OKA there is even less variability (1σ of 0.85% and 0.83% respectively). We find that carbonate samples can be accurately normalized to carbonate standards with significantly different absolute Me/Ca ratios. NanoSIMS intensity ratios follow counting statistics better than ± 1% (2σ) at any one spot, but conversion to Me/Ca ratios increases the uncertainty. Two factors give rise to this limitation. First, the spatial heterogeneity of nominally homogeneous standards can lead to accuracy offsets that are as large as the ranges quoted above. Second, the NanoSIMS generates higher instrumental mass fractionation relative to SIMS. The combination of three different analytical techniques demonstrates that Blue-CC and homogeneous calcite zones in OKA are promising reference materials for precise analyses. Accuracy is crucially dependent on making independent measurements on exactly the same crystal of standard used in the SIMS and NanoSIMS machines.

Item Type:Article
Related URLs:
URLURL TypeDescription
Guan, Y.0000-0002-7636-3735
Adkins, J. F.0000-0002-3174-5190
Additional Information:© 2013 Elsevier B.V. Received 7 April 2012. Received in revised form 20 July 2013. Accepted 22 July 2013. Available online 29 July 2013. Editor: U. Brand. We would like to thank Daniele Cherniak, Anne Cohen, Ellen Druffel, Jonathan Erez, Glenn Gaetani, Kent Ross, and Neil Sturchio for sharing the carbonate standards and bulk analytical data. John Ferry provided the carbonate material used in testing the primary beam size on the NanoSIMS. We also thank Lindsey Hedges for advising on sample preparation. The comments of anonymous reviewers were helpful as well. This work was supported by the following grants from NOAA — MIT Seagrant Program: NA100AR4170086 “Autonomous vehicle exploration and sampling of deep-water corals” and NSF: OCE-0929272 “Collecting deep-sea corals from off of Tasmania to measure the history of Southern Ocean radiocarbon concentrations”.
Group:UNSPECIFIED, UNSPECIFIED, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
National Oceanic and Atmospheric Administration (NOAA)NA100AR4170086
Subject Keywords: NanoSIMS; Heterogeneity; Elemental ratios; Calcite; Aragonite
Record Number:CaltechAUTHORS:20131121-131800523
Persistent URL:
Official Citation:R.I. Gabitov, A.C. Gagnon, Y. Guan, J.M. Eiler, J.F. Adkins, Accurate Mg/Ca, Sr/Ca, and Ba/Ca ratio measurements in carbonates by SIMS and NanoSIMS and an assessment of heterogeneity in common calcium carbonate standards, Chemical Geology, Volume 356, 9 October 2013, Pages 94-108, ISSN 0009-2541, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42620
Deposited By: Ruth Sustaita
Deposited On:21 Nov 2013 21:46
Last Modified:10 Nov 2021 16:26

Repository Staff Only: item control page