Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes
Abstract Studying diffusion of hydrogen in nominally anhydrous minerals, like clinopyroxene, at low temperatures is a challenging task due to experimental and analytical difficulties. In this study, to overcome these problems we have produced H concentration gradients in single crystals of natural d...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2022-12-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2022GC010520 |
| _version_ | 1797638033321754624 |
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| author | Thilo Bissbort Kendra J. Lynn Hans‐Werner Becker Sumit Chakraborty |
| author_facet | Thilo Bissbort Kendra J. Lynn Hans‐Werner Becker Sumit Chakraborty |
| author_sort | Thilo Bissbort |
| collection | DOAJ |
| description | Abstract Studying diffusion of hydrogen in nominally anhydrous minerals, like clinopyroxene, at low temperatures is a challenging task due to experimental and analytical difficulties. In this study, to overcome these problems we have produced H concentration gradients in single crystals of natural diopsidic clinopyroxene by ion implantation and measured the nanoscale profiles before and after diffusion anneals using Nuclear Resonance Reaction Analysis. These steps allowed us to conduct experiments at temperatures between 195°C and 400°C. Obtained diffusion rates show a consistent Arrhenius relation DH= 5.47(±13.98) · 10−8 · exp (−115.64(±11.5) kJ mol−1/RT) m2s−1. Notably, our results lie well within the range of extrapolations from high temperature experiments (≥600°C) of previous studies. This implies that fast diffusion of hydrogen (compared to other elements) extends to low temperatures. We used these results in a non‐isothermal diffusion model that simulates the ascent of crystals (0.5, 1.0, and 2.0 mm) along two representative P‐T‐paths from 600°C to 100°C, to assess potential re‐equilibration of H contents in clinopyroxene at low temperatures. Our model highlights the need to carefully consider boundary conditions, which are a function of P‐T‐fO2, that control the concentration gradient at the crystal's rim. The results from this model help to assess, as a function of crystal size and cooling rate, when re‐equilibration must be considered. |
| first_indexed | 2024-03-11T12:56:50Z |
| format | Article |
| id | doaj.art-be93c0e04f7f47c985aa6c04317d4bcf |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:56:50Z |
| publishDate | 2022-12-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-be93c0e04f7f47c985aa6c04317d4bcf2023-11-03T17:00:34ZengWileyGeochemistry, Geophysics, Geosystems1525-20272022-12-012312n/an/a10.1029/2022GC010520Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface ProcessesThilo Bissbort0Kendra J. Lynn1Hans‐Werner Becker2Sumit Chakraborty3Institute for Geology, Mineralogy and Geophysics Ruhr‐University Bochum Bochum GermanyNow at Hawaiian Volcano Observatory United States Geological Survey Hilo HI USACentral Unit for Ionbeams and Radionuclides RUBION Ruhr‐University Bochum Bochum GermanyInstitute for Geology, Mineralogy and Geophysics Ruhr‐University Bochum Bochum GermanyAbstract Studying diffusion of hydrogen in nominally anhydrous minerals, like clinopyroxene, at low temperatures is a challenging task due to experimental and analytical difficulties. In this study, to overcome these problems we have produced H concentration gradients in single crystals of natural diopsidic clinopyroxene by ion implantation and measured the nanoscale profiles before and after diffusion anneals using Nuclear Resonance Reaction Analysis. These steps allowed us to conduct experiments at temperatures between 195°C and 400°C. Obtained diffusion rates show a consistent Arrhenius relation DH= 5.47(±13.98) · 10−8 · exp (−115.64(±11.5) kJ mol−1/RT) m2s−1. Notably, our results lie well within the range of extrapolations from high temperature experiments (≥600°C) of previous studies. This implies that fast diffusion of hydrogen (compared to other elements) extends to low temperatures. We used these results in a non‐isothermal diffusion model that simulates the ascent of crystals (0.5, 1.0, and 2.0 mm) along two representative P‐T‐paths from 600°C to 100°C, to assess potential re‐equilibration of H contents in clinopyroxene at low temperatures. Our model highlights the need to carefully consider boundary conditions, which are a function of P‐T‐fO2, that control the concentration gradient at the crystal's rim. The results from this model help to assess, as a function of crystal size and cooling rate, when re‐equilibration must be considered.https://doi.org/10.1029/2022GC010520diffusionhydrogenclinopyroxeneequilibrationlow‐temperature |
| spellingShingle | Thilo Bissbort Kendra J. Lynn Hans‐Werner Becker Sumit Chakraborty Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes Geochemistry, Geophysics, Geosystems diffusion hydrogen clinopyroxene equilibration low‐temperature |
| title | Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes |
| title_full | Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes |
| title_fullStr | Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes |
| title_full_unstemmed | Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes |
| title_short | Hydrogen Diffusion in Clinopyroxene at Low Temperatures (195°C–400°C) and Consequences for Subsurface Processes |
| title_sort | hydrogen diffusion in clinopyroxene at low temperatures 195°c 400°c and consequences for subsurface processes |
| topic | diffusion hydrogen clinopyroxene equilibration low‐temperature |
| url | https://doi.org/10.1029/2022GC010520 |
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