Revising the shock classification of meteorites

The current shock classification scheme of meteorites assigns shock levels of S1 (unshocked) to S6 (very strongly shocked) using shock effects in rock‐forming minerals such as olivine and plagioclase. The S6 stage (55–90 GPa; 850–1750 °C) relies solely on localized effects in or near melt zones, the...

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Bibliographic Details
Published in:Meteoritics & planetary science 2017-06, Vol.52 (6), p.1216-1232
Main Authors: Fritz, Jörg, Greshake, Ansgar, Fernandes, Vera A
Format: Article
Language:English
Subjects:
Asteroids
Classification
Lunar meteorites
Meteorites
Meteors & meteorites
Mineralogy
Minerals
Moon
Olivine
Plagioclase
Preservation
Recrystallization
Rocks
Temperature
Velocity
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Summary:The current shock classification scheme of meteorites assigns shock levels of S1 (unshocked) to S6 (very strongly shocked) using shock effects in rock‐forming minerals such as olivine and plagioclase. The S6 stage (55–90 GPa; 850–1750 °C) relies solely on localized effects in or near melt zones, the recrystallization of olivine, or the presence of mafic high‐pressure phases such as ringwoodite. However, high whole rock temperatures and the presence of high‐pressure phases that are unstable at those temperatures and pressures of zero GPa (e.g., ringwoodite) are two criteria that exclude each other. Each type of high‐pressure phase provides a minimum shock pressure during elevated pressure conditions to allow the formation of this phase, and a maximum temperature of the whole rock after decompression to allow the preservation of this phase. Rocks classified as S6 are characterized not by the presence but by the absence of those thermally unstable high‐pressure phases. High‐pressure phases in or attached to shock melt zones form mainly during shock pressure decline. This is because shocked rocks (
ISSN:1086-9379
1945-5100
DOI:10.1111/maps.12845