Conference Agenda

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Presentations including 'bajnai'

1.2-1 Methods in Geochemistry and Mineralogy
Time: 14/Sept/2022: 10:30am-12:45pm · Location: A1

12:00pm - 12:15pm
43_1.2-1: 6
Topics: 1.2 Methods in Geochemistry and Mineralogy

A new approach for high-precision triple oxygen isotope analyses of CO2

Andreas Pack, Malte Seefeld, Oliver Jäger, Greta Viktoria Simon, David Bajnai

Universität Göttingen, Germany

Detection of small variations in triple oxygen isotope ratios (Δ’17O) of rocks, minerals, and water has opened new applications in the field of isotope geochemistry (1,2). A long-standing problem is extending the approach to CO2 and carbonates because of analytical difficulties getting precise Δ’17O of CO2. Direct measurement of Δ’17O of CO2 by means of high-resolution gas source mass spectrometry has been successfully demonstrated but requires measurement times of days for reaching a precision <10 ppm (3). Here, we present data of high-precision analyses of carbonate-derived CO2 and CO2 from the conversion of air O2 using a tunable infrared diode laser absorption spectroscopy (TILDAS) attached to a custom-built inlet system controlled by free software (PHP, Python, JavaScript, CSS, HTML) and low-cost electronic hardware, i.e., Raspberry Pi. With this device, we now achieve an external reproducibility as small as ±5 ppm. This opens new application fields, of which some will be presented.

1. A. Pack and D. Herwartz, The triple oxygen isotope composition of the Earth mantle and understanding Δ17O variations in terrestrial rocks and minerals. Earth Planet. Sci. Lett. 390, 138-145 (2014).

2. E. Barkan and B. Luz, High precision measurements of 17O/16O and 18O/16O ratios in H2O. Rapid Commun. Mass Spectrom. 19, 3737-3742 (2005).

3. G. A. Adnew, et al., Determination of the triple oxygen and carbon isotopic composition of CO2 from atomic ion fragments formed in the ion source of the 253 Ultra High‐Resolution Isotope Ratio Mass Spectrometer. Rapid Commun. Mass Spectrom. 33, 1363-1380 (2019).



5.5-2 Deciphering past climates and biogeochemical cycles with geochemical proxy archives
Time: 15/Sept/2022: 9:00am-10:15am · Location: A2

9:00am - 9:15am
52_5.5-2: 1
Topics: 5.5 Deciphering past climates and biogeochemical cycles with geochemical proxy archives

Isotope fractionation mechanisms involved in carbonate formation revealed by high-precision triple oxygen isotope analyses

David Bajnai1, Oliver Jäger1, Daniel Herwartz2, Andreas Pack1

1Geowissenschaftliches Zentrum, Georg-August-Universität Göttingen, Goldschmidtstraße 1, 37077 Göttingen, Germany; 2Institut für Geologie und Mineralogie, Universität zu Köln, Zülpicher Str. 49b, 50674 Köln, Germany

The oxygen (δ18O) and clumped (47) isotope composition of carbonates are widely used proxies for palaeotemperature. However, Earth surface carbonates are rarely formed in isotope equilibrium but often show oxygen and clumped isotope compositions that do not accurately reflect their crystallisation temperature. Isotopic disequilibrium commonly observed in biogenic carbonates and speleothems is inherited from the dissolved inorganic carbon pool of their parent solutions. A combination of isotope systems, e.g., 47δ18O, 4748, can uncover and correct for such kinetic effects [1].

The analysis of the 17O/16O ratio to the more commonly investigated 18O/16O ratio in carbonates — referred to as the triple oxygen isotope method — expands the traditional oxygen isotope scheme by another dimension and; thereby, allows the identification of fractionation processes involved in carbonate formation. In addition, the triple oxygen isotope method can give insight into the diagenetic history of ancient carbonates and offers the possibility of reconstructing the primary isotope compositions of altered samples [2].

Here, we report triple oxygen isotope ratios (Δ17O) of various altered and unaltered biogenic (e.g., brachiopods, belemnites) and abiogenic (e.g., speleothems, laboratory precipitates) carbonates. The high-precision measurements were performed on CO2 gas from acid digestion, using tunable infrared laser differential absorption spectrometry (TILDAS) [3]. Based on the results, we will discuss what combination of kinetic isotope fractionation and diagenetic processes could have played a part in the formation of the investigated carbonates.

[1] Bajnai et al., 2020, Nat Comms; [2] Wostbrock et al., 2020, GCA; [3] Pack et al., this conference.



Goldschmidt Lecture 2021 Daniel Herwartz "Beyond isotope proxies: employing triple oxygen isotope systematics in the water cycle and in chemical sediments as quantitative tool"
Time: 15/Sept/2022: 12:15pm-12:45pm · Location: B

12:15pm - 12:45pm
Goldschmidt-Lecture | Award 2021
Goldschmidt: 1
Topics: Plenary Lecture

Beyond isotope proxies: employing triple oxygen isotope systematics in the water cycle and in chemical sediments as quantitative tool

Daniel Herwartz1, Claudia Voigt2, Mohammed El-Shenawy1, Katharina Deussen1, Swea Klipsch1, David Bajnai3, Michael Staubwasser1, Carsten Münker1

1Univerität zu Köln, Germany; 2Aix Marseille Univ, CNRS, CEREGE, France; 3Georg-August-Universität Göttingen, Germany

Carbonate classic and clumped isotope ratios (δ18O and Δ47) are used to reconstruct paleotemperature. However, kinetic isotope effects (KIE) induce a bias on absolute temperature reconstructions. High precision δ17O measurements provide a refinement proxy to identify the direction and magnitude of KIEs in carbonates. Progress on this new proxy will be discussed.

The basic concept is similar to the combination of conventional oxygen and hydrogen isotope analyses in water. Combined δ18O and δ2H analyses are commonly used to approximate the magnitude of KIEs during evaporation. Triple oxygen isotope measurements in water are now used in a similar fashion. The simultaneous utilization of both trajectories provides a powerful approach to reconstruct quantitative paleoclimate information. We applied this approach to extracted water from ancient gypsum formed in the Atacama Desert and in Cyprus during the Messinian Salinity Crisis. Quantitative information on paleo-humidity and palaeohydrology are obtained. Effectively, this information is derived by quantifying KIE.

In this example, the KIE is related to diffusion of water molecules through air. Other examples of KIE include the breaking of chemical bonds, molecular mixing effects or steady states. Triple oxygen isotope trajectories allow to distinguish between such fundamental processes. Respective concepts will be explained using examples from chert and phosphate triple oxygen isotope systematics.

 
 
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