Varre Sai: The recent Brasilian fall

ZUCOLOTTO M.E.; ANTONELLO L; VARELA M.E.; SCORZELLI R; MUNAYCO P.; DOS SANTOS E.; LUDKA, IZABEL

EARTH, MOON, AND PLANETS

SPRINGER

Año: 2012 vol. 109 p. 43 - 53

0167-9295

Varre-Sai, the most recent Brazilian meteorite fall, on June 19th, 2010 at Varre-Sai, in Rio de Janeiro State, Brazil (205104100S; 41440.8000W). At least eight masses (total *3.5 kg) were recovered. Most are totally covered by fusion crust. The exposed interior is of light-grey colour with a few dark shock veins. Five thin polished and etched sections were prepared from a slice weighing 35 g on deposit at the National Museum/ UFRJ. It consists mostly of chondrules ranging in size from 0.35 to *2.2 mm, and chondrule fragments enclosed in a crystalline matrix. The matrix consists of tiny isolated subhedral and anhedral crystals and opaque minerals that are intergrown with broken chondrules. The chondritic texture is poorly defined with chondrule textures that vary from non-porphyritic to porphyritic ones. The essential minerals are olivine (Fa25±0.2) and low- Ca pyroxene (Fa21.66±0.2Wo1.4). Accessory minerals are plagioclase, apatite, Fe?Ni metal phases, troilite, chromite and magnetite. Mo¨ssbauer spectroscopy analysis confirms that the mineral phases are olivine, pyroxene, troilite and kamacite/taenite. Chemical data indicate that Varre-Sai is a member of the low iron L chondrite group. The observed texture and mineral phases led us to classify Varre-Sai as an equilibrated petrologic type 5. The shock features of the minerals (undulatory extinction, planar structure and numerous cracks), as well as plagioclase partial or totally transformed to maskelynite, suggest a shock stage S4. Also, some post-impact metamorphic processes could be inferred from the meta-sulfide conjoint grains that show complex mixtures of kamacite?taenite?tetrataenite and troilite.