کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8907200 | 1634673 | 2018 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
A re-assessment of the oxidation state of iron in MORB glasses
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم زمین و سیاره ای (عمومی)
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چکیده انگلیسی
The oxidation state of Fe, Fe/3+ΣFe (where ΣFe=Fe2++Fe3+), in glass samples of mid-ocean ridge basalt (MORB), from a wide range of localities, was determined by XANES spectroscopy to be 0.10(2) (n=42). This value is lower than that reported previously by XANES, 0.16(1) (n=103), but consistent with the most recent value determined by redox titrations, 0.11(2) (n=104), all for similar sets of samples. We attribute the anomalously high XANES value of 0.16 to a calibration error resulting from the interpretation of Mössbauer spectra and the resulting Fe/3+ΣFe values of the standards. Our alternative interpretation removes the problem of resolving Fe/3+ΣFe values <â¼0.1 in basaltic glasses, produces isomer shift and quadrupole splitting values for Fe3+ that are independent of Fe3+/ΣFe (as is the case for Fe2+), and gives Fe/3+ΣFe values that are consistent with the thermodynamically expected dependence on oxygen fugacity (fO2). Fe/3+Fe2+ is related to fO2 for our synthetic MORB composition by the temperature independent expression ÎQFM=4logâ¡(Fe3+/Fe2+)+4.23(5), where ÎQFM is the fO2 in log units relative to the quartz-fayalite-magnetite buffer. The average fO2 of natural MORB was estimated to be QFM+0.1.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 483, 1 February 2018, Pages 114-123
Journal: Earth and Planetary Science Letters - Volume 483, 1 February 2018, Pages 114-123
نویسندگان
Andrew J. Berry, Glen A. Stewart, Hugh St.C. O'Neill, Guilherme Mallmann, J. Fred W. Mosselmans,