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Katherine Gibson
Washington University in St. Louis
Department of Earth and Planetary Sciences
Advisor: Research Professor Bradley Jolliff
Abstract
The NWA 773 clan is a group of lunar meteorites that contain three prominent lithologies of lunar volcanic and related intrusive rocks; olivine gabbro cumulate, olivine phyric basalt, and a breccia. The basalt lithology is well represented by a large lithic clast in NWA 3333. The NWA 773 clan has a unique geochemical signature among lunar mare basalt meteorites. The unique geochemical signature indicates the lithologies are related and share a common source, which has been proposed to be similar to Apollo 14 green volcanic glasses. Extensive olivine analyses were taken in the VLT olivine phyric basalt. The olivine in the basalt contains prominent zoning of Fe and Mg consistent with olivine generations; coarse phenocrysts, finer phenocrysts, and matrix olivine. High precision nickel and cobalt electron-microprobe analyses were taken in the generations of olivine in the basalt and the cumulus olivine in the olivine gabbro cumulate. Variations in nickel concentrations correspond to the inferred sequence of crystallization of olivine generations. The cores of the cumulus olivine had significantly less nickel (~100-200 ppm) than the olivine in the basalt (~400-500 ppm). Crystallization modeling indicates the Apollo 14 green glass composition is a good candidate for a parent melt. The olivine-phyric basalt lithology component and the olivine-gabbro cumulate appear to be related by a common liquid line of descent, although radiometric ages indicate they were not contemporaneous. The basalt is likely to represent derivation from a similar, but more primitive parent melt than that of the cumulate.
Katherine Gibson is currently a second year graduate student at Washington University in St. Louis in the Department of Earth and Planetary Sciences. Katherine studies the petrology of planetary materials. She is from Moline, Illinois and aspires to become a professor some day. Katherine was a geology major at Indiana University and became interested in planetary materials during an internship at NASA Johnson Space Center where she studied the mineralogy and petrology of a suite of CV and CK carbonaceous chondrite meteorites.
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