16 Undergraduate Research (Posters)

Monday, 18 May 2020
8:30 AM - 5:30 PM
Lake Superior Ballroom KJ

IT IS BETTER TO BE METEORITE THAN METEOR-WRONG:ANALYSIS AND CLASSIFICATION OF POTENTIAL IRON METEORITE SPECIMEN

Paper number: 16-18
Program: Theme Sessions
Time: 8:30 AM – 5:30 PM

Authors

Abstract

The purpose of this study was to determine if a specimen collected in western Campeche, Mexico was an iron meteorite. This objective was accomplished by identifying its physical attributes and using a JEOL field emissions-electron microprobe analyzer (FE-EMPA) for compositional analysis. The visual and structural attributes of the specimen pass the iron meteorite requirements: 1) dark coloration, 2) irregular shape, 3) surficial depressions are observed, 4) leaves a brown streak on an unglazed white ceramic tile, 5) no bubbles, holes, or sedimentary strata are evident, 6) a weak magnet determines that the specimen is magnetically attractive, and 7) it has a relatively high density of 7.54 g/cm3. All of which are consistent with iron meteorites. A sample of the specimen was polished and etched with ferric chloride acid and displays features that are consistent with Widmanstätten pattern, the bands (or lamellae) representing the interfingering crystals of low-Ni kamacite and higher-Ni taenite phases often observed in iron meteorites. Widmanstätten patterns are also observed in backscatter analysis images. The sample was analyzed using WDS (wavelength-dispersive spectrometry) and EDS (energy-dispersive spectrometry). The WDS analysis indicated alternating bands of 27 and 6.5 weight percent Ni, with the remainder primarily made up of Fe in both areas (70 and 91 weight percent, respectively). This indicates the presence of low-nickel kamacite and higher-nickel taenite phases. In addition to Widmanstätten pattern, six sites of high P with the Ni and Fe were identified in EDS data. This suggests the presence of the meteoric-mineral Schreibersite (Fe, Ni)2P or it’s high-pressure-polymorph Allabogdanite (Fe, Ni)2P. The data is consistent with iron meteorites, and a classification as a group IAB-MG (main group) coarse octahedrite iron meteorite with carbonaceous inclusions.

Geological Society of America Abstracts with Programs. Vol. 52, No. 5

doi: 10.1130/abs/2020NC-348113

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