Determination of the equilibrium fO2 in bulk samples of H, L, and LL ordinary chondrites by solid-state electrochemistry

1,2Valentin O. Osadchii, 3Mark V. Fedkin, 2Evgeniy G. Osadchii
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12919]
1Department of Geochemistry, The Faculty of Geology, Moscow State University, Moscow, Russia
2Laboratory of High Temperature Electrochemistry, The Institute of 3Experimental Mineralogy, The Russian Academy of Science, Chernogolovka, Moscow Region, Russia
4Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennyslvania, USA
Published by arrangement with John Wiley & Sons

High-temperature solid-state electrochemistry techniques (EMF method) were used to measure the oxygen fugacity (fO2) of the ordinary chondrites Ochansk (H4), Savtschenskoje (LL4), Elenovka (L5), Vengerovo (H5), and Kharkov (L6). The fO2 results are presented in the form of the following equations:

[not displayed here due to technical reasons]

It was found that fO2 regularly increases from H chondrites to LL chondrites. Measured fO2 are ~1.5 higher than those previously calculated from mineral assemblages. Kharkov (L6) is a little more oxidized than Elenovka (L5) in agreement with the progressive oxidation model. At the same time, Ochansk (H4) is more oxidized than Vengerovo (H5) and exhibits a slightly different slope compared to other chondrites and at T > 1200 K, becomes more reduced than Kharkov (L6) or Elenovka (L5). Measured oxygen fugacity values of meteorites fall within (0.1–1.0)·log fO2 of one another. The possible explanation of discrepancies between measured and calculated values is discussed.

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