UBÁ

Stony

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CHONDRITE

ORDINARY

H-L-LL

H

-

5

S1/2

W1

BRAZIL - MG

1960

Equilibrated Ordinary Chondrite H5 with low shock stage S1-2 and slight terrestrial weathering W1

PETROGRAPHY:

Under optical microscope, two thin sections were analyzed and showed Ubá as an unbrecciated ordinary chondrite containing a light mm-sized clast set within brownish-gray host with generally readily discernible equilibrated chondrules. Composed predominantly of orthopyroxene, olivine, FeNi metal (kamacite), troilite and interstitial albitic feldspar (<50 µm). Minor Ca-rich pyroxene (pigeonite and augite), taenite, and tetrataenite phases occur. Dark and light regions were observed with the same petrologic texture exhibiting a low shock stage S1 to S2 due to the presence of sharp and undulatory extinction of olivine and presence of Newman lines in kamacite. Troilite is essentially unaltered and most metal is fresh with few oxidized grains (W1).

GEOCHEMISTRY:

Electron microprobe analysis yields: Host: olivine Fa20.0±0.9 (41); low Ca pyroxene Fs17.1±0.5Wo1.4±0.7 (22); Ca-rich pyroxene Fs12.2±3.6Wo29.1±15.2 (16); plagioclase Ab77.7±3.1An15.9±4.3Or6.67±3.12 (15), Co in Kamacite 4.82±0.02 mg/g (16). Clast: low-Ca pyroxene Fs13.8±1.2Wo1.36±0.7 (10), plagioclase Ab77.0±1.78An17.7±2.9Or5.3±1.57 (10).

CLASSIFICATION:

H5 ordinary chondrite. Weathering (W1) and slightly shocked (S1-2)

CLASSIFIERS:

M. E. Zucolotto and A. A. Tosi

HISTORY:

A 36 g sample of the meteorite was found next to an old card labelled "Ubá" in the MNRJ on a date prior to the fire. The piece was spared from the fire because it was at the IGEO/UFRJ for analysis. On the card was written that the meteorite was found in 1960 with an initial total mass of 84.5 g, located at Mineralogy collection of the Faculty of Philosophy of USP, and this sample was donated by Prof. Ruy Ribeiro Franco and labeled "44-MT." The mass given to the MNRJ was 36 g, but only 24.4 g are remaining.

All information that does not have a specific source was extracted from the Meteoritical Bulletin Database.

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