Thermal and crystallization history of olivine-gabbroic shergottite Northwest Africa (NWA) 13227: a link between poikilitic and gabbroic shergottites?
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Benaroya, Sophie.
Thermal and crystallization history of olivine-gabbroic shergottite Northwest Africa (NWA) 13227: a link between poikilitic and gabbroic shergottites?. Retrieved from
https://doi.org/doi:10.7282/t3-a32d-5730Export
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TitleThermal and crystallization history of olivine-gabbroic shergottite Northwest Africa (NWA) 13227: a link between poikilitic and gabbroic shergottites?
Date Created2022
Other Date2022-10 (degree)
Extent1 online resource (135 pages) : illustrations
DescriptionMartian meteorites are the only samples currently available on Earth to study Mars. Most martian meteorites are igneous in origin. Understanding the formation of these igneous rocks, and any potential links between different types of igneous groups can provide insight into mantle and crust composition and evolution, including early differentiation, convection, volatile content, and planetary differentiation. Martian meteorite Northwest Africa (NWA) 13227 represents an olivine-gabbroic shergottite, a relatively new shergottite group, which differs from previously described gabbroic shergottites due to their high quantities of olivine. It holds special significance because it may represent a potential link between gabbroic and poikilitic shergottites. NWA 13227 is comprised of phenocrystic, oscillatory zoned pyroxene and olivine, set in a matrix of maskelynite, Fe-Cr-Ti oxides, phosphates, and sulfides. It displays both gabbroic and poikilitic textures in 2D from back-scattered electron images, and in 3D from X-ray Computed Tomography (XCT) imaging. Its rare earth element (REE) profile indicates that it falls under the enriched shergottite group with a (La/Yb)CI = 1.13, similar to enriched poikilitic shergottites and gabbroic shergottites. Based on the Ti/Al ratio of pyroxene, phosphorous zoning in olivine, and minor components in phosphates and oxides, we infer that NWA 13227 began crystallizing under redox conditions of -2.6 QFM and temperatures of ~1157°C, consistent with conditions in Mars’ lower crust/upper mantle. The sample finished crystallizing at or near the surface under redox conditions of -0.5 QFM and temperatures ~857°C. The volatile ratios in apatites indicate that NWA 13227 experienced de-gassing during the last stages of crystallization. Modeled Lu-Hf and Sm-Nd sources give an estimated age for NWA 13227 of between ~150 – 260 Ma. The mineralogy, petrology, and mineral chemistry of NWA 13227 indicate affinities to both poikilitic and gabbroic shergottites, and thus, suggest that these groups share a common origin or magmatic plumbing system, like those proposed for enriched poikilitic and gabbroic shergottites. NWA 13227 is the first sample that suggests a link between gabbroic and poikilitic shergottites.
NoteM.S.
NoteIncludes bibliographical references
Genretheses
LanguageEnglish
CollectionSchool of Graduate Studies Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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