Effects of mineralogy on Δ47 and Δ48 of carbonate-derived CO2 below analytical resolution

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F25%3A10169509" target="_blank" >RIV/00025798:_____/25:10169509 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1016/j.gca.2025.06.004" target="_blank" >https://doi.org/10.1016/j.gca.2025.06.004</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.gca.2025.06.004" target="_blank" >10.1016/j.gca.2025.06.004</a>

Result language

angličtina

Original language name

Effects of mineralogy on Δ47 and Δ48 of carbonate-derived CO2 below analytical resolution

Original language description

Due to the lack of direct methods capable of determining the abundance of isotopologues containing multiple heavy isotopes within the crystal lattice, carbonates are typically reacted with phosphoric acid to produce CO&lt;inf&gt;2&lt;/inf&gt; analyte for clumped isotope analyses. This reaction is associated with fractionations of both bulk oxygen and clumped isotopes. Accurate knowledge of the effect of cation substitution on the degree of isotopic clumping in the carbonate phase (Δ&lt;inf&gt;63&lt;/inf&gt;, Δ&lt;inf&gt;64&lt;/inf&gt;) and on acid fractionation factors (Δ&lt;inf&gt;47&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt;, Δ&lt;inf&gt;48&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt;) is crucial for accurate temperature reconstructions based on clumped isotope measurements (Δ&lt;inf&gt;47&lt;/inf&gt;, Δ&lt;inf&gt;48&lt;/inf&gt;) of CO&lt;inf&gt;2&lt;/inf&gt; extracted from various carbonate mineralogies. Previous studies have yielded contradicting results on the effect of carbonate mineralogy on both Δ&lt;inf&gt;47&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt; acid fractionation factors and the validity of a universal Δ&lt;inf&gt;47&lt;/inf&gt;MINUS SIGN T relationship, and, so far, a systematic investigation of mineralogy-specific effects on Δ&lt;inf&gt;48&lt;/inf&gt; and Δ&lt;inf&gt;48&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt; is lacking. In this study, we have analyzed the dual clumped isotope composition of stochastic and non-stochastic calcites, aragonites, dolomites, witherites&apos; and siderites with unprecedented long-term repeatabilities (1SDs) of 8.6 and 28.1 ppm for Δ&lt;inf&gt;47&lt;/inf&gt; and Δ&lt;inf&gt;48&lt;/inf&gt;, respectively. In order to facilitate complete acid digestion of dolomite and siderite in a reasonable timeframe, an acid digestion temperature of 110 oC was used for these minerals instead of the 90 oC applied to calcite, aragonite and witherite. A set of calcite samples was reacted at both temperatures to determine the calcite-specific difference in acid digestion-related fractionation factors between 90 and 110 oC, yielding Δ&lt;inf&gt;47,110-90&lt;sup&gt;o&lt;/sup&gt;C&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt; = -0.0147 +- 0.002 % and Δ&lt;inf&gt;48,110-90&lt;sup&gt;o&lt;/sup&gt;C&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt; = -0.0148 +- 0.006 %o (2SEs, n = 8). After projecting Δ&lt;inf&gt;47&lt;/inf&gt; and Δ&lt;inf&gt;48&lt;/inf&gt; results from stochastic dolomite and siderite to the carbon dioxide equilibrium scale (CDES90) using the calcite-specific Δ&lt;inf&gt;i,110-90&lt;sup&gt;o&lt;/sup&gt;C&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt;, calcite, aragonite, dolomite, witherite and siderite exhibit statistically indistinguishable Δ&lt;inf&gt;47,CDES90&lt;/inf&gt; and Δ&lt;inf&gt;48,CDES90&lt;/inf&gt; values, with weighted averages of 0.1850 +- 0.0042 %o and 0.1255 +- 0.0130 %o (weighted 2SEs, n = 15), respectively. In addition, Δ&lt;inf&gt;47,CDES90&lt;/inf&gt; and Δ&lt;inf&gt;48,CDES90&lt;/inf&gt; values of non-stochastic aragonites (n = 2), (proto-)dolomites (n = 2) and witherite (n = 1) correspond to calcite equilibrium values predicted by their independently known formation temperatures (Fiebig et al., 2024). Natural dolomites and siderites of unknown formation temperature are also indistinguishable from the calcite equilibrium line. Overall, these results imply that calcite, aragonite, dolomite and witherite share indistinguishable Δ&lt;inf&gt;47&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt;, Δ&lt;inf&gt;48&lt;/inf&gt;&lt;sup&gt;ASTERISK OPERATOR&lt;/sup&gt; and Δ&lt;inf&gt;63&lt;/inf&gt;MINUS SIGN Δ&lt;inf&gt;64&lt;/inf&gt;MINUS SIGN T relationships. As a consequence, the calcite-specific equilibrium Δ&lt;inf&gt;47,CDES90&lt;/inf&gt;MINUS SIGN Δ&lt;inf&gt;48,CDES90&lt;/inf&gt;MINUS SIGN T relationships of Fiebig et al. (2024) can be reliably applied to aragonite, dolomite, and witherite. More precipitation experiments under controlled conditions are necessary to clarify with more confidence if these relationships are also valid for siderite.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Geochimica Et Cosmochimica Acta

ISSN

0016-7037

e-ISSN

1872-9533

Volume of the periodical

401

Issue of the periodical within the volume

15 July 2025

Country of publishing house

GB - UNITED KINGDOM

Number of pages

15

Pages from-to

89-103

UT code for WoS article

001512528800001

EID of the result in the Scopus database

2-s2.0-105008030821