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Impact‐related thermal effects on the redox state of Ca‐pyroxene
Author(s) -
McCanta M. C.,
Dyar M. D.
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.12793
Subject(s) - pyroxene , mineral redox buffer , redox , mössbauer spectroscopy , crystallization , oxidation state , analytical chemistry (journal) , mineralogy , geology , olivine , materials science , chemistry , inorganic chemistry , crystallography , geochemistry , mantle (geology) , metallurgy , metal , environmental chemistry , organic chemistry
Oxidation is observed in Ca‐pyroxene subjected to a range of shock pressures (21–59 GP a). Changes in the pyroxene redox ratio as measured by the changes in %Fe 3+ ranged from 2–6 times the starting composition. Mössbauer and reflectance spectroscopy record the changing Fe 3+ concentration as a preferential oxidation of Fe 2+ in the M2 crystallographic site. The oxidation is also accompanied by mechanical changes in the pyroxene crystals including fracturing, linear defects, and twinning. As oxygen fugacity is often calculated using mineral redox ratios and thought to represent the prevailing f O 2 during crystallization, it is imperative to recognize that the f O 2 values measured in impact‐derived materials may represent that of the impact and not the magma source region.