ITAPURANGA

Iron

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ACHONDRITE

COARSE OCTAHEDRITE

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IAB

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BRAZIL - GO

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Iron Meteorite - Coarse Octahedrite IAB.

PETROGRAFIA:

The dimensions of the Itapuranga meteorite are 75x65x43 cm, in approximately orthogonal directions, and the mass is 628 kilos. The regmagliptic grooves are well evident, with the intensity of the recesses and the irregularity in the distribution of the concavities appearing as the most notable character. Mineralogically, kamacite and taenite, occurring irregularly interpenetrated, in a mosaic texture, are the main constituents. Its internal structure was identified by attacking a 45x30 mm fragment, immersed in 20% nitric acid alcoholic solution. After 15 minutes of attack, the structure formed by centimetric crystals of kamacite, with a very pale grayish color and very bright, interspersed with darker and more attacked crystals, characterizing Taenite, was immediately highlighted. The crystals are irregularly interpenetrated in a mosaic texture. Another mineral identified was schreibersite, which also occurs in the form of rhabdite. They are relatively common, recognizable by their light tan color, appearing in the form of small submillary lenses or irregular venules 0, I to 0.2 mm wide by 8 to 10 mm long. Other times, they are equidimensional and irregularly shaped, about 0.2 to 0.3 mm in size. Note also the presence of lines forming variable angles, from 30 to 40 °, corresponding sometimes to the Neumann lines, in the areas where kamacite predominates, sometimes to those of Widmanstãtten, where the nickel content is higher. From a structural point of view, siderite is a typical coarse octahedrite (width of the kamacite lamellae, 1.5 mm). Source: Svisero et al. (1980).

GEOQUÍMICA:

Chemical data were obtained by neutron activation analysis, while Ni was determined by atomic absorption. (Ni, 6.6%; Ga, 96.9 ppm; Ge, 478 ppm; Ir, 2.8 ppm). Source: Svisero et al. (1980).

CLASSIFICAÇÃO:

From a structural point of view, the meteorite is classified as a coarse octahedrite, keeping similarity, according to Prof. W.S. Curvello, with the siderite called Santa Luzia, also from Goiás. The similarity concerns the nickel content and the presence of schreibersite. However, the values obtained for some trace elements clearly show that these are two distinct meteorites. Chemically, the high levels in Ga and Ge leave no doubt as to the inclusion of the Itapuranga meteorite in Group IA of the siderites. Likewise, the concentrations of Ir and Ni are compatible with this group. For information, just access the link to the article referred to http://www.ppegeo.igc.usp.br/index.php/bigusp/article/view/2855. Source: Svisero et al. (1980).

CLASSIFICADORES:

D.P. Svisero, S.E. Amaral and C.B. Gomes

HISTÓRIA:

The Itapuranga meteorite (longitude 50 ° 9 'W, latitude 15 ° 35' S), State of Goiás, was found at Fazenda Curral de Pedra, distant 18 km west of the city of Itapuranga. The meteorite was found semi-buried by the owner's wife, emerging just over a foot. The piece was acquired by Mr. Vas11io Semenov, who transported it to São Paulo and later sold it to the Institute of Geosciences at the University of São Paulo. Thanks to financial assistance granted by the São Paulo State Research Support Foundation, it was possible to purchase it and travel by the authors to the region, in order to study the location of the fall. Source: Svisero et al. (1980).

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