Compositional and structural mapping of Northwest Africa 15507 angrite
Angrite meteorites represent interesting sampling of planetary crustal environments. Quench-textured angrites with strong crystal zoning originated from the shallow surface region, with evidence of reducing conditions during solidification. Plutonic angrites have more coarse-grained igneous and metamorphic textures with comparatively less zoning and are interpreted as having equilibrated at greater depth. Plutonic angrites contain the minerals magnetite Fe3O4 comprised of Fe2+ and Fe3+, and rhönite, where Fe3+ is required by inspection of mineral stoichiometry. NWA 15507 is a plutonic angrite with a microgabbroic texture (mean grainsize ∼1.4 mm) composed of zoned Al-Ti-augite, Ca-bearing olivine, anorthite, with accessory kirschsteinite, rhönite, hercynite, low-Ni kamacite, merrillite, Ti-free magnetite and troilite [1]. Rhönite analyzed by electron-probe microanalysis (EPMA) has the formula Ca2.04(Mg0.32Fe2+4.25Fe3+0.47Ti0.33Al0.61)(Si3.74Al2.26)O20, where Fe3+ was estimated by stoichiometric analysis. During preliminary cathodoluminescence (CL) analysis, complex subgrain and oscillatory zoning was observed in the anorthite. In this study we use a combined approach of electron probe microanalysis (EPMA), cathodoluminescence (CL), electron-backscatter diffraction (EBSD), and laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) to further investigate the anorthite and distribution of Fe3+ in NWA 15507.
Citation Information
Publication Year | 2024 |
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Title | Compositional and structural mapping of Northwest Africa 15507 angrite |
DOI | 10.1093/mam/ozae044.008 |
Authors | Heather A. Lowers, Paul C. Carpenter, Jay Michael Thompson, Anthony Irving |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Microscopy and Microanalysis |
Index ID | 70259682 |
Record Source | USGS Publications Warehouse |
USGS Organization | Central Mineral and Environmental Resources Science Center; Geology, Geophysics, and Geochemistry Science Center |