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An isotopologue-enabled model (∆47, ∆48) for describing thermal fluid-carbonate interaction in open and closed diagenetic systems
  • +5
  • Philip T Staudigel,
  • Chelsea Pederson,
  • H.J.L. (Jeroen) van der Lubbe,
  • Miguel Bernecker,
  • Mattia Tagliavento,
  • Amelia Davies,
  • Adrian Immenhauser,
  • Jens Fiebig
Philip T Staudigel
Goethe University Frankfurt

Corresponding Author:[email protected]

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Chelsea Pederson
University of Southern Mississippi
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H.J.L. (Jeroen) van der Lubbe
Vrije Universiteit Amsterdam
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Miguel Bernecker
Goethe-Univeristät Frankfurt
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Mattia Tagliavento
Unknown
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Amelia Davies
Department of environmental sciences, Stockholm University
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Adrian Immenhauser
Univ. Bochum, Germany
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Jens Fiebig
Institut für Geowissenschaften
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Abstract

The geochemical and ultrastructural properties of thermally altered skeletal carbonate are expected to be compromised to varying degrees by disequilibrium processes between solids and the ambient aqueous fluids. When assessing the alteration history of carbonates, it is important to apply models that quantitatively describe these diagenetic processes on multiple geochemical systems, such that they can be identified in natural samples. Carbonate clumped isotope analysis provides a unique tool for validating such models and can be combined with other geochemical tools/proxies to more comprehensively describe the processes and products. Here, we have analyzed bivalve shells that have undergone hydrothermal alteration (experimental diagenesis) in high water/rock ratio experiments at 130 and 160{degree sign}C, demonstrating that non-linear changes in ∆47 and ∆48 values can be attributed to heterogeneous replacement of precursor carbonates. Importantly, this model predicts decoupled ∆47 and ∆48 values, despite all reactions occurring at clumped isotope equilibrium with respect to the experimental temperature. We demonstrate that the rapid, thermally induced re-equilibration occurs in a “closed system” with minimal exchange with the ambient fluid, similar to the results of heating experiments conducted without an extraneous fluid. Later stages of alteration occur in an “open system” wherein internal fluid is exchanged with the external fluid at a similar rate to recrystallization and neomorphism. In these experiments, some oxygen from the original inorganic-organic composite-biomineral is inherited, indicating restrictions on the availability of fluid oxygen. Our experiments and models validate a novel application for dual-clumped isotopes for reconstructing hydrothermal temperatures and fluid δ18O compositions.
11 Jul 2023Submitted to ESS Open Archive
23 Jul 2023Published in ESS Open Archive