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PARANAÍBA
Stony
TYPE:
CLASS:
CLAN:
GROUP:
SUBGROUP:
TYPE PET:
SHOCK STG:
WEATHERING:
COUNTRY:
YEAR:
DESCRIPTION:
CHONDRITE
ORDINARY
H-L-LL
L
-
6
S3 or more
-
BRAZIL - MT
1956
Equilibrated Ordinary Condrite L6, brecciated and with signs of high shock stage.
PETROGRAPHY:
In the hand sample, the meteorite exhibits a differentiated texture, mainly because it presents light, circular and angular fragments, quite varied in size, cut by a dark vein and large dark areas. The clear areas are due to recrystallization, with few discernible cores in the middle of the main mass. The dark areas are clearly derived from the shock metamorphism, partially fused, and no longer exhibits the chondritic texture. The dark color of the veins is the result of the abundance of fine-grained opaques. Thus, the meteorite is a monomythic breach of shock origin. Mineralogical considerations made by Keil et al. (1977) indicates that the dark shock veins formed at pressures greater than 430kb and a temperature of 1500-1700ºC, while the light fragments represent less altered portions of the rock and experienced pressures of approximately 200kb and temperatures below 900ºC. Source: Gomes & Keil (1980).
GEOCHEMISTRY:
According to Keil et al. (1977), the clear areas of the meteorite, which represent the portion least affected by the shock event, mainly consists of olivine Fa23.7 and pyroxene Fs20.7, with smaller amounts of oligoclase glass (maskelinite) Ab83.1An11.3Or5.6 , FeNi and troilite. Chromite is an accessory mineral. The dark areas, representing the regions most affected by shock metamorphism, are essentially formed by glass with varied composition, droplets and veins of the FeNi metal, as well as phases of olivine and orthopyroxene that are weakly anisotropic to perfectly isotropic. Isotropic phases are generally colorless when viewed through transmitted light, but are sometimes light to dark brown. Source: Gomes & Keil (1980).
CLASSIFICATION:
The total and mineralogical composition of the clear portion of the meteorite is consistent with L group of the chondrites, especially the minerals olivine, plagioclase, orthopyroxene and chromite are in accordance with this classification. The chemical L group is confirmed by the total chemistry and the Feº / Ni (5.05), Fe / SiO2 (0.52) and Feº / Fe (0.31) ratios, as well as the total concentration of total Fe in the meteorite (20.86%) and total FeNi of 7.92. The type 6 petrographic classification, according to Van Schmus & Wood (1967), is due to the uniformity and compositional homogeneity of ferromagnesian minerals, the scarcity of visible chondrules and the highly recrystallized texture. Source: Gomes & Keil (1980).
CLASSIFIERS:
Not reported by the Meteoritical Bulletin Database. A preliminary description was given by Arruda (1962) and Amaral (1962). Ramdohr (1973) identified the presence of chalcopyrrotite and mackinawite as accessory phases. A detailed study on the Paranaíba meteorite was carried out by Keil et al. (1977) and Gomes & Keil (1978).
HISTORY:
In 1956, Paranaíba fell 70 km from Paranaíba on the Can-Can farm. The meteorite of approximately 100 kg was recovered from a hole 2 meters deep, but much of this material was destroyed by the neighborhood. Like Bendegó, the population of the region attributed the lack of rain to the removal of the meteorite. People went on a pilgrimage to the place where the meteorite fell to rain, says an interviewed lady, and when they returned from there they got wet because it was raining. A cross was erected there. In the literature there are two meteorites in the same region, and the history of the two meteorites seems to be confused, since it records that a good fragment of Cacilândia went to the National Museum, however this sample does not exist, only Paranaíba. Virtually nothing is known about the history of Cacilândia. Description obtained in the documents of National Museum.
All information that does not have a specific source was extracted from the Meteoritical Bulletin Database.
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