MONTES CLAROS DE GOIÁS
BRAZIL - GO
Equilibrated Ordinary Chondrite H5 with moderate shock stage S4 and terrestrial weathering W2
Two thin sections were analyzed. Chondrules are not well defined. Chondrules, with apparent diameter ranging from 0.5 to 1.5 mm (mean 0.7 mm) set in medium grained matrix consisting of orthopyroxene, olivine, plagioclase and minor clinopyroxene. The major pyroxene crystals in the whole section are orthopyroxenes. Olivine show undulatory extinction, planar fractures and mosaicism. The meteorite shows thin melt veins, some of them with small melt pockets and presence of melted metal and troilite flakes. Opaque phases are represented by Fe,Ni alloys (alpha and gamma) and sulphides both in chondrules and in the matrix. Neumann lines can be seen on many large kamacite crystals and around 20 to 30% of the metal has already been oxidized. This generates an orange to brown staining on the silicate phase also many fractures filled with oxide. The presence of feldsphatic, chromite and phosphate grains up to 100 μm in size.
Electron microprobe analysis yielded: olivine Fa18.6±0.6 (18), low-Ca pyroxene Fs16.7±0.6En82.2±0.7Wo1.1±0.5 (17), high-Ca pyroxene Fs12.9±2.8En65.1±0.7Wo22.0±8.1 (5); plagioclase Ab80.4±2.1An12.2±1.2Or7.5±1.2 (10), Co in kamacite 0.46±0.02 (30).
H5, weathering (W2) and moderately shocked (S4) ordinary chondrite.
M. E. Zucolotto and A. A. Tosi
In September 2018, Dione Pantaleão, a manager of the Corrego Mestre farm located ~30 km northwest of Montes Claros de Goias city, Goias State, noticed a large stone in an area without any other rocks. In May 2019, the large and unusually heavy specimen was shown to the farm’s owner, Eduardo F. de Melo, who then contacted the meteorite collector Carlo Bottelli to seek assistance in identifying the possible meteorite. In July 2019, Bottelli and Eduardo took the meteorite to an astronomy meeting (5º Encontro Paulista de Astronomia - Sertaozinho, São Paulo), where its authenticity was confirmed by Andre L R Moutinho and Maria Elizabeth Zucolotto.
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