Nanosims Investigation of Presolar Material in Chondrites of the Cr

Abstract

Introduction: Silicates and oxides are among the most abundant types of presolar dust grains observed in primitive solar system matter [e.g.,1,2]. The CR chondrite clan, consisting of the CR, CH, and CB chondrite groups, contains some of the most primitive meteorites, with characteristic bulk 15 N-enrichments [5,6]. High abundances of presolar silicates and carbonaceous grains were recently reported in individual CR chondrites [5–7]. Noble gas data imply the presence of carbonaceous presolar grains also in CH chondrites [8]. No presolar grains have been found in the CH/CB chondrite Isheyevo yet, but this meteorite contains chondritic clasts displaying very high 15 N-enrichments [9,10]. Investigating the content of presolar matter in meteorites of these groups can shed light on the distribution of presolar grains and molecular cloud material in the solar nebula. Samples and Experimental: With the NanoSIMS 50 ion probe in Mainz, we performed ion imaging of 5×5 µm²-to 10×10 µm²-sized matrix areas in a thin section of the CR2 chondrite NWA 852 to search for C-and O-bearing presolar grains and to characterize the N-isotopic composition. and 27 Al 16 O – were measured in multi-collection to identify presolar silicate and oxide grains. Additionally, 12 C – , 13 C – , 12 C 14 N – , 12 C 15 N – , and 28 Si – were measured on a subset of matrix material studied for O in NWA 852 to search for C-and N-isotopic anomalous phases. It is planned to extend our ion imaging studies to a polished section of the CH/CB b chondrite Isheyevo. Results and Discussion: 23 presolar silicate and 8 oxide grains were identified in NWA 852, representing abundances of 98 ppm for silicates and 70 ppm for oxides, respectively. C and N isotopes have been analyzed in ~600 µm² of matrix. The average δ 15 N is +(178±48) ‰, and up to +(1122±148) ‰ in

Cite this paper

@inproceedings{Hoppe2009NanosimsIO, title={Nanosims Investigation of Presolar Material in Chondrites of the Cr}, author={Pernille Hoppe}, year={2009} }