Studies of Brazilian Meteorites of the Museu Nacional - I: Petrography and Mineralogy of the Santa Vitória do Palmar, Rio Grande do Sul, L 3 Chondrite Meteorite

Resumen

The Santa Vitória do Palmar chondrite was found in 2003 in Rio Grande do Sul State, Brazil (33°30’56’’S, 53°24’65’’W). It consists of three masses (34kg, 4.34kg and 1.57kg). Showing, a black rusty- colored fusion crust and several distinct depressions (regmaglypts). It is not know if this find is correlated with a bright fireball seen in 1997 at the same region. Optical investigation shows that the meteorite has a well developed chondritic texture typical of type 3 chondrite. There are chondrules of different types (radial- pyroxene, barred-olivine and cryptocrystalline; porphyritic olivine, porphyritic pyroxene and porphyritic olivine- pyroxene; granular olivine, and compound chondrules) very well delineated many times surrounded by troilite and Huss matrix. Mineralogical studies reveal that the meteorite contains chiefly olivine Fa (0.5-35.2), pyroxene Fs (0.5-31.6), with small amount of Fe-Ni metal (kamacite, taenite and plessite) and troilite. Based on texture features and chemical data, the Santa Vitoria do Palmar meteorite is classified as an unequilibrated member of the L group chondrite. The well defined chondritic texture and the presence of glassy material indicate a petrologic type of 3 subtype 3.4-3.6, shock-stage S3/4 and weathering grade W1/2.