C. Pirim^a, M.A. Pasek^b, D.A. Sokolov^a, A.N. Sidorov^a, R. Gann^a and T.M. Orlando^a

^aSchool of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA
^bDepartment of Geology, University of South Florida, Tampa, FL 33620, USA

This work presents a comprehensive investigation of schreibersite inclusions within iron-poor and iron-rich meteorites, and of the associated intrinsic low-temperature oxidation products observed after exposure to terrestrial weathering. First, a thermodynamic equilibrium modeling of the oxidation of schreibersite was carried out and showed that oxidation is mostly limited to the surface in the absence of other ions and/or water. This oxidation occurs rapidly (less than a few weeks) and is mediated by the atmosphere, forming primarily iron oxides and iron phosphates. Second, detailed analyses of meteorite schreibersite inclusions and synthetic schreibersite surrogates (Fe₃P and Fe₂NiP) were performed using surface characterization techniques such as micro-Raman spectroscopy, atomic force microscopy (AFM), electrostatic force microscopy (EFM), electron microprobe analysis (EPMA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Such thorough analyses are required as all prebiotic reactivity studies performed nowadays use meteoritic samples that have been somewhat exposed to Earth weathering. We find that, while the meteorite samples have not been introduced directly into water, they all bear significant oxidation signatures that appear to be similar for both studied short-term and long-term natural weathering corrosion processes. In addition, we find that synthetic schreibersite samples have similar surface and sub-surface chemistry and are reasonable chemical proxies for natural schreibersite. The thorough analytical studies detailed in this paper provide a chemical model for schreibersite oxidation products.

Reference
Pirim C, Pasek MA, Sokolov DA, Sidorov AN, Ganna R and Orlando TM (in press) Investigation of schreibersite and intrinsic oxidation products from Sikhote-Alin, Seymchan, and Odessa meteorites and Fe3P and Fe2NiP synthetic surrogates. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.05.027]
Copyright Elsevier

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