Thermal modeling of shock melts in four Martian meteorites; implications for preservation of Martian atmosphere and crystallization of high-pressure minerals from shock melts - MacEwan Users Only

Shaw, C. S., & Walton, E. L. (2013). Thermal modeling of shock melts in four Martian meteorites; implications for preservation of Martian atmosphere and crystallization of high-pressure minerals from shock melts.
Metadata
TitleThermal modeling of shock melts in four Martian meteorites; implications for preservation of Martian atmosphere and crystallization of high-pressure minerals from shock melts
Author(s)Shaw, Cliff S, J.; Walton, Erin L.
Date2013
Keyword(s)achondrites, argon, atmosphere, chemical fractionation
DescriptionThe distribution of shock melts in four shergottites, having both vein and pocket geometry, has been defined and the conductive cooling time over the range 2500 degrees C to 900 degrees C calculated. Isolated 1 mm (super 2) pockets cool in 1.17 s and cooling times increase with pocket area. An isolated vein 1X7 mm in Northwest Africa (NWA) 4797 cools to 900 degrees C in 4.5 s. Interference between thermal haloes of closely spaced shock melts decreases the thermal gradient, extending cooling times by a factor of 1.4 to 100. This is long enough to allow differential diffusion of Ar and Xe from the melt. Small pockets (1 mm (super 2) ) lose 2.2% Ar and 5.2% Xe during cooling, resulting in a small change in the Ar/Xe ratio of the dissolved gas over that originally trapped. With longer cooling times there is significant fractionation of Xe from Ar and the Ar/Xe ratio increases rapidly. The largest pockets show less variation of Ar/Xe and likely preserve the original trapped gas composition. Considering all of the model calculations, even the smallest isolated pockets have cooling times greater than the duration of the pressure pulse, i.e., >0.01 s. The crystallization products of these shock melts will be unrelated to the peak shock pressure experienced by the meteorite.
Peer ReviewedYes
Type of ItemJournal Articles
DOI10.1111/maps.12100
Publication InformationShaw, C. J., & Walton, E. (2013). Thermal modeling of shock melts in Martian meteorites; implications for preserving Martian atmospheric signatures and crystallization of high-pressure minerals from shock melts. Meteoritics & Planetary Science, 48(5), 758-770. doi:10.1111/maps.12100
MacEwan Users Onlyhttps://library.macewan.ca/cgi-bin/SFX/url.pl/86S
LanguageEnglish
RightsAll Rights Reserved