Constraining uncertainty in boron isotope systematics using a Bayesian inversion engine reveals contrasting parameter sensitivities
Constraining uncertainty in boron isotope systematics using a Bayesian inversion engine reveals contrasting parameter sensitivities
Physical parameters within boron isotope systematics form a complex interplay that determine the boron isotopic composition of rocks, minerals, and fluids, but to date, providing constraints on uncertainty within boron equilibrium isotope modelling remains elusive. This underlying uncertainty limits the potency of boron isotopes as a tool for detecting fluid-rock exchange. A new equilibrium boron mineral-fluid fractionation modelling approach, named EquiB, coupled with a Bayesian inversion engine is presented, providing robust and reproducible constraints on the uncertainty of physical parameters encoded into a boron isotopic composition of a rock in equilibrium with a fluid. We demonstrate the validity of our approach by applying the model to several basalt-fluid and peridotite-fluid exchange scenarios. The model output generates multi-dimensional posterior probability distributions that show temperature is the greatest control on mineral-fluid fractionation in all applied scenarios. At high temperatures (defined as >50 °C) pH-dependent fractionation is negligible, but at low temperatures (defined as <50 °C) pH-dependent fractionation is a control on boron isotopic compositions. At geologically reasonable conditions other parameters such as salinity, fluid density, and pressure have little effect on the extent of boron mineral-fluid fractionation. Model outputs agree with experimentally derived fractionation factors at typical hydrothermal conditions but diverge at low temperatures. This approach provides robust constraints of parameter uncertainty, enabling meaningful interpretation of boron isotope analyses and the ability to fingerprint isotopic compositions with greater confidence.
Bayesian inversion, Boron isotopes, Equilibrium isotope fractionation, Fluid-rock exchange, Parameter estimation, Serpentinization
Evans, Aled D.
41a3083e-fb13-4f18-a35b-c0763afa7716
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Teagle, Damon A..H.
396539c5-acbe-4dfa-bb9b-94af878fe286
6 February 2024
Evans, Aled D.
41a3083e-fb13-4f18-a35b-c0763afa7716
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Teagle, Damon A..H.
396539c5-acbe-4dfa-bb9b-94af878fe286
Evans, Aled D., Foster, Gavin L. and Teagle, Damon A..H.
(2024)
Constraining uncertainty in boron isotope systematics using a Bayesian inversion engine reveals contrasting parameter sensitivities.
Chemical Geology, 648, [121953].
(doi:10.1016/j.chemgeo.2024.121953).
Abstract
Physical parameters within boron isotope systematics form a complex interplay that determine the boron isotopic composition of rocks, minerals, and fluids, but to date, providing constraints on uncertainty within boron equilibrium isotope modelling remains elusive. This underlying uncertainty limits the potency of boron isotopes as a tool for detecting fluid-rock exchange. A new equilibrium boron mineral-fluid fractionation modelling approach, named EquiB, coupled with a Bayesian inversion engine is presented, providing robust and reproducible constraints on the uncertainty of physical parameters encoded into a boron isotopic composition of a rock in equilibrium with a fluid. We demonstrate the validity of our approach by applying the model to several basalt-fluid and peridotite-fluid exchange scenarios. The model output generates multi-dimensional posterior probability distributions that show temperature is the greatest control on mineral-fluid fractionation in all applied scenarios. At high temperatures (defined as >50 °C) pH-dependent fractionation is negligible, but at low temperatures (defined as <50 °C) pH-dependent fractionation is a control on boron isotopic compositions. At geologically reasonable conditions other parameters such as salinity, fluid density, and pressure have little effect on the extent of boron mineral-fluid fractionation. Model outputs agree with experimentally derived fractionation factors at typical hydrothermal conditions but diverge at low temperatures. This approach provides robust constraints of parameter uncertainty, enabling meaningful interpretation of boron isotope analyses and the ability to fingerprint isotopic compositions with greater confidence.
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Accepted/In Press date: 18 January 2024
e-pub ahead of print date: 28 January 2024
Published date: 6 February 2024
Keywords:
Bayesian inversion, Boron isotopes, Equilibrium isotope fractionation, Fluid-rock exchange, Parameter estimation, Serpentinization
Identifiers
Local EPrints ID: 490319
URI: http://eprints.soton.ac.uk/id/eprint/490319
ISSN: 0009-2541
PURE UUID: b4a4fa54-ded4-42ec-b364-e51e2088cbd7
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Date deposited: 23 May 2024 16:47
Last modified: 24 May 2024 02:01
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Author:
Aled D. Evans
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