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X-ray Spectromicroscopy of Mineral Intergrowths in the Santa Catharina Meteorite

DOI: 10.1111/j.1751-908X.2010.00038.x DOI Help

Authors: Paul Schofield (Natural History Museum) , Andrew Smith (STFC, Daresbury Laboratory) , Fred Mosselmans (Diamond Light Source) , Hendrik Ohldag (Advanced Light Source) , Andreas Scholl (Advanced Light Source) , Simone Raoux (Advanced Light Source) , Gordon Cressey (Natural History Museum) , Barbara Cressey (University of Southampton) , Paul Quinn (Diamond Light Source) , Caroline Kirk (University of Loughborough) , Simon Hogg (Loughborough University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Geostandards And Geoanalytical Research

State: Published (Approved)
Published: June 2010

Abstract: This work describes the application of microfocus X-ray absorption spectroscopy (XAS) and X-ray photo-emission electron microscopy (XPEEM) to the study of the complex mineralogical intergrowths within the Santa Catharina meteorite. The Santa Catharina meteorite of this study (BM52283 from the meteorite collection of the Natural History Museum, London, UK) primarily comprises a taenite bulk host phase (Fe:Ni ratio = 70.9 ± 0.8%:29.1 ± 0.8%) with a set of oxide-bearing cloudy zone textured regions (Fe:Ni:O ratio = 40.4 ± 0.3%:49.0 ± 0.7%:10.6 ± 0.8% at the core and Fe:Ni:O ratio = 34.4 ± 1.5%:42.7 ± 0.6%:22.9 ± 1.8% towards the rims) and numerous schreibersite (Fe:Ni:P ratio = 38.6 ± 1.6%:38.4 ± 0.9%:23.0 ± 0.5%) inclusions. Between the schreibersite and the taenite are rims up to 50 μm across of Ni-rich kamacite (Fe:Ni ratio = 93.4 ± 0.4%:6.6 ± 0.5%). No chemical zoning or spatial variations in the Fe and Ni speciation was observed within either the schreibersite or the kamacite phases. The oxide-bearing cloudy zone textured regions mostly comprise metallic Fe-Ni alloy, predominantly tetrataenite. Within the oxide phases, the Fe is predominantly, but not entirely, tetrahedrally co-ordinated Fe3+ and the Ni is octahedrally co-ordinated Ni2+. Structural analysis supports the suggestion that non-stoichiometric Fe2NiO4 trevorite is the oxide phase. The trevorite:tetrataenite ratio increases at the edges of the oxide-bearing cloudy zone textured regions indicating increased oxidation at the edges of these zones. The spatial resolution of the XPEEM achieved was between 110 and 150 nm, which precluded the study of either the previously reported ∼ 10 nm precipitates of tetrataenite within the bulk taenite or any antitaenite.

Journal Keywords: Santa Catharina Meteorite; Antitaenite; X-Ray Photo-Emission Electron Microscopy; Xpeem; Microfocus X-Ray ; Pectroscopy; Non-Destructive Analysis

Subject Areas: Environment

Instruments: I18-Microfocus Spectroscopy