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Mechanism of Solid-State Clumped Isotope Reordering in Carbonate Minerals from Aragonite Heating Experiments

Chen, Sang and Ryb, Uri and Piasecki, Alison M. and Lloyd, Max K. and Baker, Michael B. and Eiler, John M. (2019) Mechanism of Solid-State Clumped Isotope Reordering in Carbonate Minerals from Aragonite Heating Experiments. Geochimica et Cosmochimica Acta, 258 . pp. 156-173. ISSN 0016-7037. doi:10.1016/j.gca.2019.05.018.

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The clumped isotope compositions of carbonate minerals are subject to alteration at elevated temperatures. Understanding the mechanism of solid-state reordering in carbonate minerals is important in our interpretations of past climates and the thermal history of rocks. The kinetics of solid-state isotope reordering has been previously studied through controlled heating experiments of calcite, dolomite and apatite. Here we further explore this issue through controlled heating experiments on aragonite. We find that Δ_(47) values generally decrease during heating of aragonite, but increase by 0.05–0.15‰ as aragonite starts to transform into calcite. We argue that this finding is consistent with the presence of an intermediate pool of immediately adjacent singly-substituted carbonate ion isotopologues (‘pairs’), which back-react to form clumped isotopologues during aragonite to calcite transformation, revealing the existence of kinetically preferred isotope exchange pathways. Our results reinforce the ‘reaction-diffusion’ model as the mechanism for solid-state clumped isotope reordering in carbonate minerals. Our experiments also reveal that the reordering kinetics in aragonite is faster than in calcite and dolomite, making its clumped isotope composition highly susceptible to alteration during early diagenesis, even before conversion to calcite.

Item Type:Article
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URLURL TypeDescription
Chen, Sang0000-0001-8941-0791
Lloyd, Max K.0000-0001-9367-2698
Additional Information:© 2019 Elsevier. Received 16 October 2018, Accepted 13 May 2019, Available online 22 May 2019. We thank George Rossman for help with Raman spectroscopy and providing calcite samples. The XRD measurements were performed in Nathan Lewis’s lab at Caltech. We thank Alex Lipp for help with the calcite reordering experiments. S.C. would like to acknowledge financial support from China Scholarship Council for Ph.D. study at Caltech. This work was supported by NSF EAR Award #1322058 to J.M.E.
Funding AgencyGrant Number
China Scholarship CouncilUNSPECIFIED
Subject Keywords:Aragonite; Calcite; Clumped isotopes; Phase transition; Solid-state reordering; Reaction-diffusion model
Record Number:CaltechAUTHORS:20190522-154638196
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Official Citation:Sang Chen, Uri Ryb, Alison M. Piasecki, Max K. Lloyd, Michael B. Baker, John M. Eiler, Mechanism of solid-state clumped isotope reordering in carbonate minerals from aragonite heating experiments, Geochimica et Cosmochimica Acta, Volume 258, 2019, Pages 156-173, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95715
Deposited By: George Porter
Deposited On:22 May 2019 23:03
Last Modified:16 Nov 2021 17:14

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