Browsing by Author "Ziegler, Karen"
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- ItemHydrous olivine alteration on Mars and Earth(2020) Vaci, Zoltan; Agee, Carl B.; Herd, Christopher D. K.; 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.
- ItemThe Northwest Africa 10416 olivine-phyric Martian basalt: product of magma mixing, assimilation and alteration(2016) Herd, Christopher D. K.; 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.