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Browsing Faculty of Arts & Science by Author "Agee, Carl B."
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- ItemHydrous olivine alteration on Mars and Earth(2020) Váci, Zoltán; Agee, Carl B.; Herd, Christopher; Walton, Erin L.; Tschauner, Oliver; Ziegler, Karen; Prakapenka, Vitali B.; Greenberg, Eran; Monique-Thomas, SylviaHydrous alteration of olivine macrocrysts in a Martian olivine phyric basalt, NWA 10416, and a terrestrial basalt from southern Colorado are examined using SEM, EPMA, TEM, and µXRD techniques. The olivines in the meteorite contain linear nanotubes of hydrous material, amorphous areas, and fluid dissolution textures quite distinct from alteration identified in other Martian meteorites. Instead, they bear resemblance to terrestrial deuteric alteration features. The presence of the hydrous alteration phase Mg-laihunite within the olivines has been confirmed by µXRD analysis. The cores of the olivines in both Martian and terrestrial samples are overgrown by unaltered rims whose compositions match those of a separate population of groundmass olivines, suggesting that the core olivines are xenocrysts whose alteration preceded crystallization of the groundmass. The terrestrial sample is linked to deep crustal metasomatism and the “ignimbrite flare-up” of the Oligocene epoch. The comparison of the two samples suggests the existence of an analogous relatively water-rich magmatic reservoir on Mars.
- ItemShock effects in new Martian olivine basalt Northwest Africa 10416: distinct from shergottites but akin Northwest Africa 8159(2016) Walton, Erin L.; Tschauner, Oliver; Herd, Christopher; Agee, Carl B.Martian meteorites record a range of shock effects associated with hypervelocity impact events on their parent body. The purpose of this study is to characterize shock deformation and transformation effects within and adjacent to shock veins in NWA 10416 and in non-veined regions of the host rock. New phases produced by shock, through crystallization or solid-state transfromation, can be used to estimate the shock pressure and the duration of the shock pulse to better understand the impact processes experienced by this sample.
- ItemThe Northwest Africa 10416 olivine-phyric Martian basalt: product of magma mixing, assimilation and alteration(2016) Herd, Christopher; Walton, Erin L.; Ziegler, Karen; Vaci, Zoltan; Agee, Carl B.; Muttik, NeleThe Northwest Africa (NWA) 10416 olivine-phyric basalt is distinct from other Martian basalts in several ways, including in the record of pre-terrestrial alteration preserved within it. Here we report the details of the mineralogy, petrology and geochemistry of this intriguing specimen, which suggest that the history of the rock includes assimilation of previously altered igneous phases.
- ItemThe Northwest Africa 10416 olivine-phyric shergottite: a product of multiple impact events on Mars?(2016) Walton, Erin L.; Herd, Christopher; Tschauner, Oliver; Agee, Carl B.Martian meteorites record shock effects associated with hypervelocity impact events on their parent planet, manifest as shock deformation or transformation of igneous minerals. The timing of Mars ejection can be approximated by the CRE age; however, the timing of shock metamorphism has been addressed by few studies. Recently, the first shergottite to preserve crystalline igneous feldspar was reported. In 2015, another martian olivine basalt, NWA 10416, was described. As one of the few martian meteorites to preserve igneous feldspar, NWA 10416 records shock conditions distinct from those of other shergottites within which plagioclase has been amorphized or melted. The purpose of this study is to characterize shock in NWA 10416.