FAINA

Iron

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ACHONDRITE

COMPLEX OCTAHEDRITE

IAB

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BRAZIL - GO

2011

Iron Meteorite - Complex Octahedrite IAB with strongly plessitic characteristic.

PETROGRAFIA:

The polished and etched sections exhibit a complex plessitic matrix with at least two different size orders from the Widmanstätten standard. The bandwidth of the α axes is typically 80 µm wide and 10-25 or 1-4 times the width, respectively. It also has some large kamacite bands unrelated to the Widmanstätten plessitic pattern, as they are formed by nucleated kamacite bands and growth around schreibersite crystals. The shafts are oriented uniformly in at least two austenite crystals. The ferrite (iron) of the axes shows the boundaries of the sub-grain, but no Neumann line. Troilite occurs as few small, spaced nodules. The bandwidth of the kamacite spindles was measured using a composite image obtained under an optical microscope that was connected to a computer and analyzed with the ImageJ software. The size distribution of the bandwidths shows a bimodal distribution of kamacite axes. The large population of kamacita is formed by a single long network of kamacita that borders larger plessite fields, while smaller kamacite fields are more visible associated with small plessite fields. This smaller size of plessitic domains sometimes has an incoherent orientation due to many small phosphide crystals that nucleate kamacite crystals. Source: Zucolotto et al. (2015).

GEOQUÍMICA:

(J. T. Wasson, UCLA) INAA: 8.67% Ni; 0.87% Co; 28 ppm Cr; 186 ppm Cu; 23.4 ppm of Ga; 83 ppm Ge; 13 ppm As; 6 ppm of Ru; 3.91 ppm Ir; 1.40 ppm Au. Main phases composition (IP Ludka, IGEO-UFRJ) WDS / EPMA: kamacite (Ni = 5.56 ± 0.4; Co = 0.61; N = 20), taenite (Ni = 28.8 ± 1.4 ; Co = 0.61; N = 16), phosphides (Ni = 27.7 ± 1.2; P = 16.68 ± 0.7, N = 12), all in weight%.

CLASSIFICAÇÃO:

Faina is a plessitic octahedrite that resembles Ballinoo, Wiley, Crathèus, although the Ni content is very low for a plessitic octahedrite and other chemical contents of Ni, Ga, Ge and Au. This detail places the Faina meteorite separate from the IIC meteorites and classifies it as belonging to the IAB group - complex without a relative, and although similar to EET 83000, it does not show visible silicates. Two distinct cooling events should also be considered, where one precipitates schreibersite with the formation of kamacite and the other shows a precipitation and growth of the Widmanstätten pattern in two stages, arguing that the meteorite forms over a wide temperature range. Zucolotto et al. (2015).

CLASSIFICADORES:

J. T. Wasson, M.E. Zucolotto and I. P. Ludka

HISTÓRIA:

Found in a backyard when Mr. G. Rodrigues dug a hole for septic tank of his house. He suspected that the mass was a meteorite after watching a TV program about meteorites. Purchased by Andre Moutinho on 31 Aug 2013.

Todas as informações que não possuírem fonte especifica, foram extraídas do Meteoritical Bulletin Database.

Todas as imagens possuem direitos autorais.

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