Santa Lucia (2008) (L6) chondrite, a recent fall: composition, noble gases, nitrogen and cosmic ray exposure age

MAHAJAN R.; VARELA, M.E; JORON JL,

EARTH, MOON, AND PLANETS

SPRINGER

Lugar: Berlin; Año: 2016 vol. 117 p. 65 - 76

0167-9295

Abstract The Santa Lucia (2008)?one the most recent Argentine meteorite fall, fell in SanJuan province, Argentina, on 23 January 2008. Several masses (total *6 kg) were recovered.Most are totally covered by fusion crust. The exposed interior is of light-grey colour. Chemicaldata[olivine (Fa24.4) and low-Ca pyroxene (En77.8 Fs20.7 Wo1.6)] indicate that Santa Luica (2008)is a member of the low iron L chondrite group, corresponding to the equilibrated petrologic type6. The meteorite name was approved by the Nomenclature Committee (NomCom) of theMeteoritical Society (Meteoritic Bulletin, no. 97). We report about the chemical composition ofthe major mineral phases, its bulk trace element abundance, its noble gas and nitrogen data. Thecosmic ray exposure age based on cosmogenic 3He, 21Ne, and 38Ar around 20 Ma is comparableto one peak of L chondrites. The radiogenic K?Ar age of 2.96 Ga, while the young U, Th?He areof 1.2 Ga indicates that Santa Lucia (2008) lost radiogenic 4He more recently. Low cosmogenic(22Ne/21Ne)c and absence of solar wind noble gases are consistent with irradiation in a largebody. Heavy noble gases (Ar/Kr/Xe) indicated trapped gases similar to ordinary chondrites.Krypton and neon indicates irradiation in large body, implying large pre-atmospheric meteoroid