CAPÃO DO LEÃO
BRAZIL - RS
Ordinário Chondrite L5
Two polished thin sections were exhamined under OM and EPMA, showing discernible chondrules and chondrules fragments. Chondrule types include BO, RP, PO, POP and GOP. One chondrule is fully enveloped by a wide troilite rim. Chondrule sizes range from 0.3 to 1.5 mm with average diameter of 0.78 mm. Clinoenstatite grains are present in PP chondrules. Plagioclase occur as small grains, few larger than 50 µm in size. Many metal grains show dark plessite etch, most of them have tetrataenite rim. Neuman lines in kamacite are present. Troilite is polycrystalline. Olivine and pyroxene show weak mosaicism, planar fractures and undulatory extinction, suggesting shock stage S3/4. Less than 20% of Few Fe-Ni metal present oxidation and no evidence of weathering in silicate minerals indicating weathering grade W1.
Electron microprobe: olivine Fa26.1 ± 0.9 (n=13); low Ca pyroxene Fs20.5±1.1Wo0.98±0.5 (n=9); plagioclase Ab80.4±1.75An10.2±0.60Or9.42±2.0 (n=8). Kamacite Ni=6.79±0.23 wt. %, Co=0.835±0.16 wt. % (n=7).
L5 brecciated ordinary chondrite. Weathering (W1) and moderated shocked (S3/4)
M. E. Zucolotto and A. A. Tosi
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