scholarly journals Simultaneous determination of 87Sr/86Sr and trace-element data in otoliths and other sclerochronological hard structures

2020 ◽  
Author(s):  
Jens C. Hegg ◽  
Christopher M. Fisher ◽  
Jeffrey Vervoort

AbstractChronological data from hard structures have been instrumental in reconstructing information about the past across numerous disciplines. Isotopic and trace elemental chronologies from the depositional layers of speleothems, corals, bivalve shells, fish otoliths and other structures are routinely used to reconstruct climate, growth, temperature, geological, archeological and migratory histories. Recent in situ analytical advances have revolutionized the use of these structures. This is particularly true of fish, in which detailed origin, life-history, and migration history can be reconstructed from their otoliths. Specifically, improvements in laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) have allowed increases in temporal resolution, precision, and sample throughput. Many studies now combine multiple chemical and isotopic tracers, taking advantage of multivariate statistical methods and multiple trace-elements and isotope systems to glean further information from individual samples. This paper describes a novel laser ablation split-stream (LASS) methodology which allows simultaneous collection of the Sr isotope composition (87Sr/86Sr) and trace-elemental data from chronologically deposited carbonate samples. The study investigates the accuracy and precision of varying laser spot sizes on a marine shell standard and fish otoliths using LASS and presents a comparison to traditional “single stream methods” using pre-existing otolith data on the same samples. Our results indicate that LASS techniques can be used to provide accurate and precise data at the same laser spot sizes as previous otolith studies, thereby doubling analytical throughput, while also providing improved spatially and temporally-matched data reduction using newly developed features for the Iolite data reduction platform.

1997 ◽  
Vol 54 (9) ◽  
pp. 2068-2079 ◽  
Author(s):  
S E Campana ◽  
S R Thorrold ◽  
C M Jones ◽  
D Günther ◽  
M Tubrett ◽  
...  

The elemental composition of fish otoliths is of considerable interest to those who wish to reconstruct temperature, migration, or environmental histories of individual fish based on assays of the otolith growth sequence. However, reported differences in otolith elemental composition among studies may be due in part to performance differences among four of the most popular instruments for targeted elemental analysis: wavelength-dispersive electron microprobe (WD-EM), energy-dispersive electron microprobe (ED-EM), proton-induced X-ray emission (PIXE), and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). To rigorously compare the sensitivity, accuracy, and precision of these four analytical tools, the International Otolith Composition Experiment distributed blind-labelled real and artificial otoliths of known but varied elemental composition to eight laboratories for assay of 10 selected elements. No one instrument type was sensitive to each element, nor was any one instrument preferred for use in all assays. In general however, abundant elements such as Na and K could only be measured accurately with an electron microprobe, while the trace elements required PIXE or LA-ICPMS. Strontium could be measured with considerable accuracy and precision by WD-EM, PIXE, and LA-ICPMS. The presence of significant, and occasionally large, differences among laboratories suggests that comparisons among published studies should be made cautiously and only after appropriate calibration.


2000 ◽  
Vol 57 (6) ◽  
pp. 1232-1242 ◽  
Author(s):  
Simon R Thorrold ◽  
Stephen Shuttleworth

We applied laser ablation sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) to the analysis of trace element and isotopic signatures in fish otoliths. Manganese, Sr, and Ba profiles across juvenile Atlantic croaker (Micropogonias undulatus) otoliths, expressed as ratios to Ca, showed considerable spatial and temporal variations that were presumably reflective of variations in water chemistry over the same scales. Differences in otolith Mn:Ca ratios between adjacent rivers in Pamlico Sound, North Carolina, may be related to dissolved oxygen levels in the rivers through reductive release of Mn2+ from sediments. Strontium and Ba profiles appeared to accurately reflect differences in dissolved Sr and Ba in freshwater end-members, both between Pamlico Sound and Chesapeake Bay and between seasons within Chesapeake Bay. High-precision analyses of Sr:Ca ratios in a black drum (Pogonias cromis) otolith showed distinctive quasi-sinusoidal cycles that were correlated with validated annual bands. Analyses of Sr and Pb isotopes, in otoliths and standard reference material, respectively, found that SF-ICP-MS produced accurate and precise estimates of isotope ratios in both solution-based and laser ablation assays.


2020 ◽  
Author(s):  
Johannes Rembe ◽  
Renjie Zhou ◽  
Edward R. Sobel ◽  
Jonas Kley ◽  
Rasmus Thiede

<p>Rutile is frequently found in metamorphic and less commonly in igneous rocks, as well as sediments derived from the former rock types. It may contain enough U (typically up to ~100ppm) to be dated by U/Pb geochronology. In detrital studies, rutile U/Pb ages supplement zircon U/Pb data, as zircon age peaks often reflect magmatic activity, while rutile U/Pb age peaks can be connected to metamorphic events. Using Zr-in-rutile thermometry, one could also estimate metamorphic facies of the terrane, from which detrital rutile grains are derived. Zircon U/Pb dating provides usually a crystallization age, while rutile gives cooling ages that are dependent on the size of the diffusion domain and its cooling rate. The closure temperature has been estimated at ca. 600°C. A major challenge of rutile U/Pb geochronology is the variable amount of common Pb present and most rutile dating requires the correction for common Pb. A widely used method is the Stacey & Kramers approach, which estimates a formation age for a group of rutile grains and assigns them an age-dependent initial Pb isotope composition from the terrestrial Pb evolution curve (Stacey and Kramers, 1975). We present detrital rutile U/Pb data measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) from Mesozoic and Cenozoic units in the North Pamir in Central Asia. The laser ablation system obtains a time resolved signal of all required isotopes. Using data reduction schemes in Iolite (Paton et al., 2011) and VizualAge (Petrus and Kamber, 2012), the signal is routinely integrated to a single spot age for each ablation pit. Following a similar approach for apatite (Stockli et al., 2017), we subdivided the signal of each single spot into several time-slices and obtained data that crosses diffusion domains or compositional zones within a single rutile grain. Time slices in most cases are aligned along a Discordia in the Tera-Wasserburg diagram, enabling us to calculate a lower intercept age and initial 207Pb/206Pb ratio. We also discuss similarities and differences between these internally corrected ages and the Stacey & Kramers approach-corrected ages.</p><p> </p><p>Paton, C., Hellstrom, J., Paul, B., Woodhead, J., Hergt, J., 2011. Iolite: Freeware for the visualisation and processing of mass spectrometric data. Journal of Analytical Atomic Spectrometry 26 (12), 2508–2518.</p><p>Petrus, J.A., Kamber, B.S., 2012. VizualAge: A Novel Approach to Laser Ablation ICP-MS U-Pb Geochronology Data Reduction. Geostandards and Geoanalytical Research 36 (3), 247–270.</p><p>Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters 26 (2), 207–221.</p><p>Stockli, D.F., Boyd, P., Galster, F., 2017. Intra-grain common Pb correction in apatite by LA-ICP-MS depth profiling and implications for detrital apatite U-Pb dating. EGU General Assembly Abstract Volume.</p><p> </p>


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