M?ssbauer spectroscopy of pyroxene in the light-dark structure of the Kapoeta meteorite: implications for thermal history of the Kapoeta parent body

Frontiers in Theoretical and Applied Physics/UAE 2017

Abdu, Y.A.^1 ; Hawthorne, F.C.^2

Department of Applied Physics and Astronomy, University of Sharjah, P.O. Box 27272, Sharjah, United Arab Emirates^1

Department of Geological Sciences, University of Manitoba, Winnipeg

MB

R3T 2N2, Canada^2

关键词: Closure temperatures;    Hyperfine parameters;    Octahedral sites;    Orthopyroxene;    Single crystal x-ray diffraction;    Ssbauer spectroscopies;    Thermal history;    X-ray structure;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/869/1/012096/pdf
DOI  :  10.1088/1742-6596/869/1/012096

来源: IOP

【 摘 要 】

We report an experimental study of the intracrystalline distribution of Fe2+and Mg between the non-equivalent octahedral sites, M1 and M2, in orthopyroxene from the Kapoeta meteorite by single-crystal X-ray diffraction and Mössbauer spectroscopy. The Fe2+-Mg ordering closure temperatures obtained by X-ray structure refinement for two orthopyroxene crystals from Kapoeta (357±30 °C and 411±18 °C) are very similar to those reported for diogenites, and indicate a slow cooling rate. The powder Mössbauer spectra of the light and dark regions in Kapoeta are identical, and their hyperfine parameters are characteristic of orthopyroxene. The closure temperature obtained by Mössbauer spectroscopy for the Kapoeta orthopyroxene (744 °C) is rather high, and indicates a fast cooling rate. The results are discussed in connection with the thermal history of the Kapoeta parent body.