Fig. 2.

Data for moderately volatile elements, ordered in a sequence of increasing volatility (lithophiles are indicated by vertical bars; Ni, Au, and Ge are siderophile; all other elements are chalcophile). (a) Average matrix compositions for CV, CO, and CM chondrites. LA-ICP-MS data (and standard deviation in LA analyses) is also shown for CI1 chondrites (Alais and Orgueil). Different chondrite groups have distinct matrix lithophile abundances, which plot close to the bulk data for those groups. CV and CO matrices have very similar siderophile and chalcophile abundances. The elements most fractionated in C3 matrices are siderophiles and chalcophiles; they are significantly enriched over bulk and over matrix lithophiles. (b) Allende and Mighei have representative matrix compositions for CV3 and CM2 chondrites, respectively. LA-ICP-MS and analysis of separated matrix by solution ICP-MS show that their matrices are compositionally distinct. Allende is generally depleted compared with Mighei, and Mighei shows much less variation between siderophile/chalcophile and lithophile elements. Mighei matrix is depleted in all moderately volatile elements compared with CI. Finally, in Allende, chondrule siderophiles and chalcophiles (13) are substantially depleted compared with bulk, complementing enrichment in matrix in these elements.