Hydrogen and oxygen stable isotope signatures of goethite hydration waters by thermogravimetry-enabled laser spectroscopy [electronic resource]
Stable Isotope Hydrology; Paleoclimatology; Dehydroxylation; Mineral-Water Fractionation; Hydrous Minerals.
Saved in:
| Online Access: |
Online Access (via OSTI) |
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| Corporate Author: | |
| Format: | Government Document Electronic eBook |
| Language: | English |
| Published: |
Washington, D.C. : Oak Ridge, Tenn. :
United States. Department of Energy. ; distributed by the Office of Scientific and Technical Information, U.S. Department of Energy,
2017.
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| Subjects: |
| Summary: | Stable Isotope Hydrology; Paleoclimatology; Dehydroxylation; Mineral-Water Fractionation; Hydrous Minerals. |
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| Abstract: | The hydrogen and oxygen stable isotope composition (δ<sup>2</sup>H and δ<sup>18</sup>O values) of mineral hydration waters can give information on the environment of mineral formation. Here we present and validate an approach for the stable isotope analysis of mineral hydration waters based on coupling a thermogravimetric analyzer with a laser-based isotope ratio infrared spectroscopy instrument (Picarro L-2130i), which we abbreviate as TGA-IRIS. TGA-IRIS generates δ<sup>2</sup>H and δ<sup>18</sup>O values of liquid water samples with precision for δ<sup>2</sup>H of ± 1.2‰, and for δ<sup>18</sup>O of ± 0.17‰. For hydration waters in goethite, precision for δ<sup>2</sup>H ranges from ± 0.3‰ to 1.6‰, and for δ<sup>18</sup>O ranges from ± 0.17‰ to 0.27‰. The ability of TGA-IRIS to generate detailed water yield data and δ<sup>2</sup>H and δ<sup>18</sup>O values of water at varying temperatures allows for the differentiation of water in varying states of binding on mineral surfaces and within the mineral matrix. TGA-IRIS analyses of hydrogen isotopes in goethite yields δ<sup>2</sup>H values that reflect the hydrogen of the OH<sup>-</sup> phase in the mineral and are comparable to that made by IRMS and found in the literature. In contrast, δ<sup>18</sup>O values on goethite reflect the oxygen in OH<sup>-</sup> groups bound to Fe (Fe-OH group), and not the oxygen bound only to Fe (Fe-O group) in the mineral crystal lattice, and may not be comparable to literature δ<sup>18</sup>O values made by IRMS that reflect the total O in the mineral. TGA-IRIS presents the possibility to isotopically differentiate the various oxygen reservoirs in goethite, which may allow the mineral to be used as a single mineral geothermometer. As a result, TGA-IRIS measurements of hydration waters are likely to open new avenues and possibilities for research on hydrated minerals. |
| Item Description: | Published through SciTech Connect. 10/22/2017. "llnl-jrnl--736485" Chemical Geology 475 C ISSN 0009-2541 AM. Erik Oerter; Michael Singleton; Lee Davisson. |
| Physical Description: | p. 14-23 : digital, PDF file. |