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Determination of the equilibrium f O 2 in bulk samples of H, L, and LL ordinary chondrites by solid‐state electrochemistry
Author(s) -
Osadchii Valentin O.,
Fedkin Mark V.,
Osadchii Evgeniy G.
Publication year - 2017
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12919
Subject(s) - chondrite , mineral redox buffer , meteorite , fugacity , analytical chemistry (journal) , solid state , chemistry , physics , oxygen , mineralogy , thermodynamics , astrobiology , organic chemistry , chromatography
High‐temperature solid‐state electrochemistry techniques (EMF method) were used to measure the oxygen fugacity ( f O 2 ) of the ordinary chondrites Ochansk (H4), Savtschenskoje (LL4), Elenovka (L5), Vengerovo (H5), and Kharkov (L6). The f O 2 results are presented in the form of the following equations: log f O 2 ( Ochansk ) = ( 9.39 ± 1.64 ) − ( 3.124 ∓ 0.191 ) · 10 4 · T − 11070 < T / K < 1270 , R 2 = 0.9944log f O 2 ( Vengerovo ) = ( 6.86 ± 1.73 ) − ( 2.870 ∓ 0.196 ) · 10 4 · T − 11050 < T / K < 1230 , R 2 = 0.9942log f O 2 ( Elenovka ) = ( 8.37 ± 1.10 ) − ( 3.005 ∓ 0.124 ) · 10 4 · T − 11050 < T / K < 1230 , R 2 = 0.9979log f O 2 ( Savtschenskoje ) =( 11.36 ± 0.85 ) − ( 3.289 ∓ 0.099 ) · 10 4 · T − 11070 < T / K < 1270 ,R 2 = 0.9986log f O 2 ( Kharkov ) = ( 7.80 ± 0.44 ) − ( 2.930 ∓ 0.050 ) · 10 4 · T − 11050 < T / K < 1230 , R 2 = 0.9996It was found that f O 2 regularly increases from H chondrites to LL chondrites. Measured f O 2 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 f O 2 of one another. The possible explanation of discrepancies between measured and calculated values is discussed.