Sulfur and selenium in chondritic meteorites

Abstract— We report here new analyses of S and Se in carbonaceous chondrites (2 CIs, 11 CMs, 6 CO3s, 7 CV3s, 2 C4s, 4 CRs, and 1 CH), 2 rumurutiites, ordinary chondrites (2 Hs, 2 Ls, and 1 LL), 3 anomalous chondrites, 3 acapulcoites, 3 lodranites, and in silicate inclusions of the Landes IAB iron meteorite. To avoid problems from inhomogeneous distribution of sulfides, the same samples that had been analysed for Se by INAA were analysed for S using a Leybold Heraeus Carbon and Sulfur Analyser (CSA 2002). With the measured CI contents of 5.41% S and 21.4 ppm Se a CI S/Se ratio of 2540 is obtained. A nearly identical S/Se ratio of 2560 ± 150 is found for carbonaceous chondrites (average of falls). The average ratio of all meteorite falls analysed in this study was 2500 ± 270. These data suggest that the new S content of Orgueil with 5.41% provides a reliable estimate for the average Solar System. The new solar system abundance of S of 4.62 × 10⁵ (atoms/10⁶ Si) is in good agreement with the solar photospheric abundance of 7.21 (log (a(H)) = E12) (Anders and Grevesse, 1989). Among the 50 analysed meteorites, 24 were finds from hot (Australia, Africa) and cold (Antarctica) deserts. Weathering effects in the carbonaceous chondrites and in one lodranite from the hot deserts resulted in losses of S, Se, Na and occasionally Ni. Sulfur is apparently more affected by weathering than Se. No losses were observed in ordinary chondrite finds and in meteorites collected in the Antarctica, except for the obvious loss of Na in the CM-chondrite Y 74662. The low S-content of 0.096% in Gibson, a lodranite, is probably not representative of this group of meteorites. Gibson is a find from the Australian desert and has lost S and also Se by weathering. Two other lodranites, finds from Antarctica, have about 2% S.