An Isotope Dilution ICP‐MS Method for the Determination of Mg/Ca and Sr/Ca Ratios in Calcium Carbonate

Fernández, Diego P.; Gagnon, Alex; Adkins, Jess F.

doi:10.1111/j.1751-908x.2010.00031.x

Cited by 23 publications

(18 citation statements)

References 36 publications

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“…JCp‐1 analyses bracketed every eight sample analyses. Sr/Ca ratios were also measured repeatedly in standard materials derived from fish otoliths [ Yoshinaga et al ., ; Sturgeon et al ., ] and the NBS‐19 limestone [ Fernandez et al ., ] to ensure consistency of our Sr/Ca calibrations. As reported in Alpert et al .…”

Section: Methodsmentioning

confidence: 99%

Coral Sr‐U thermometry

et al. 2016

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Coral skeletons archive past climate variability with unrivaled temporal resolution. However, extraction of accurate temperature information from coral skeletons has been limited by "vital effects," which confound, and sometimes override, the temperature dependence of geochemical proxies. We present a new approach to coral paleothermometry based on results of abiogenic precipitation experiments interpreted within a framework provided by a quantitative model of the coral biomineralization process. DeCarlo et al. (2015a) investigated temperature and carbonate chemistry controls on abiogenic partitioning of Sr/Ca and U/Ca between aragonite and seawater and modeled the sensitivity of skeletal composition to processes occurring at the site of calcification. The model predicts that temperature can be accurately reconstructed from coral skeleton by combining Sr/Ca and U/Ca ratios into a new proxy, which we refer to hereafter as the Sr-U thermometer. Here we test the model predictions with measured Sr/Ca and U/Ca ratios of 14 Porites sp. corals collected from the tropical Pacific Ocean and the Red Sea, with a subset also analyzed using the boron isotope (δ 11 B) pH proxy. Observed relationships among Sr/Ca, U/Ca, and δ 11 B agree with model predictions, indicating that the model accounts for the key features of the coral biomineralization process. By calibrating to instrumental temperature records, we show that Sr-U captures 93% of mean annual temperature variability (26-30°C) and has a standard deviation of prediction of 0.5°C, compared to 1°C using Sr/Ca alone. The Sr-U thermometer may offer significantly improved reliability for reconstructing past ocean temperatures from coral skeletons.

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Section: Methodsmentioning

confidence: 99%

Coral Sr‐U thermometry

et al. 2016

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“…In this study, one laboratory measured Mg/Ca and Sr/Ca ratios using an improved version of the ID method described in Fernandez et al . []. The main improvements involved adapting the method to use a Neptune multicollector (MC) ICP‐MS (ThermoFinnigan) to analyze the isotope ratios of dissolved and spiked coral samples.…”

Section: Methodsmentioning

confidence: 99%

Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

Hathorne

Gagnon

Felis

et al. 2013

Geochem Geophys Geosyst

207

150

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[1] The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twentyone laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7 C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5 C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5 C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.

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“…Instrumental mass fractionation during Q-ICP-MS analysis was corrected using bracketing of enriched and natural abundance standards of known isotopic composition. The enriched isotope standard used in this part of the study was XG as described by Fernandez et al (2010); the natural abundance standards were made from dissolved natural minerals…”

Section: Isotope Labeling Using 43 Ca and 25 Mgmentioning

confidence: 99%

Isotopic tracer evidence for the amorphous calcium carbonate to calcite transformation by dissolution–reprecipitation

Giuffre

Gagnon

Yoreo

et al. 2015

Geochimica et Cosmochimica Acta

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Please cite this article as: Giuffre, A.J., Gagnon, A.C., De Yoreo, J.J., Dove, P.M., Isotopic tracer evidence for the amorphous calcium carbonate to calcite transformation by dissolution-reprecipitation, Geochimica et Cosmochimica Acta (2015), doi: http://dx. AbstractObservations that some biogenic and sedimentary calcites grow from amorphous calcium carbonate (ACC) raise the question of how this mineralization process influences composition. However, the detailed pathway and geochemical consequences of the ACC to calcite transformation are poorly constrained. This experimental study investigated the formation of calcite from ACC by using magnesium and calcium stable isotope labeling to directly probe the transformation pathway and controls on composition. Four processes were considered: dissolution-reprecipitation, solid state transformation, and combinations of these end-members. To distinguish between these scenarios, ACC was synthesized from natural isotope abundance solutions and subsequently transferred to spiked solutions that were enriched in 43 Ca and 25 Mg for the transformation to calcite.Isotope measurements by NanoSIMS determined the 43 Ca/ 40 Ca, and 25 Mg/ 24 Mg ratios of the resulting calcite crystals.Analysis of the data shows the transformation is best explained by a dissolutionreprecipitation process. We find that when a small amount of ACC is transferred, the isotopic signals in the resulting calcite are largely replaced by the composition of the surrounding spiked solution. When larger amounts of ACC are transferred, calcite compositions reflect a mixture between the ACC and initial solution end-member.Comparisons of the measurements to the predictions of a simple mixing model indicate that calcite compositions 1) are sensitive to relative amounts of ACC and the surrounding solution reservoir and 2) are primarily governed by the conditions at the time of ACC transformation rather than the initial ACC formation. Shifts in calcite composition over the duration of the transformation period reflect the progressive evolution of the local solution conditions. This dependence suggests the extent to which there is water available would change the end point composition on the mixing line. While these findings have significant geochemical implications, the question remains whether this transformation pathway is generally followed when biomineralization involves ACC or is particular to these inorganic experiments. Insights from this study nonetheless suggest that some types of compositional variability, such as 'vital effects', may be explained inpart by a co-evolution of reservoir and products over the duration of the transformation.3

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An Isotope Dilution ICP‐MS Method for the Determination of Mg/Ca and Sr/Ca Ratios in Calcium Carbonate

Cited by 23 publications

References 36 publications

Coral Sr‐U thermometry

Coral Sr‐U thermometry

Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements

Isotopic tracer evidence for the amorphous calcium carbonate to calcite transformation by dissolution–reprecipitation

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