The Campos Sales meteorite from Brazil: A lightly shocked L5 chondrite fall

The Campos Sales meteorite fell close to the town of Campos Sales in the no rtheastern Brazilian state of Ceara (7 degrees 2' S, 40 degrees 10' W) on 1 991 January 31 at 10:00 P.M. (local time). Several fragments were recovered from an area estimated to be 1 x 3 km. The stone is an ordinary L5 chondri te (Fa(25.0) and Fs(21.6)) and is lightly shocked (S1). Metal phases presen t are kamacite, tetrataenite, and antitaenite. Noble gases He, Ne, Ar, Kr, and Xe have been analyzed in two bulk samples of Campos Sales. All exposure ages based on determination of cosmogenic He-3, Ne-21, Ar-38, Kr-83, and X e-126 abundances and on the cosmogenic Kr-81/Kr-83 ratio agree well, which suggests no gas loss during cosmic-ray exposure. The cosmic-ray exposure ag e is 23.3 +/- 1.0 Ma, which falls in the range observed for L5 chondrites ( 20-30 Ma). The gas-retention ages indicate He loss that must have occurred prior to or during ejection from the L-chondrite parent body.