Abstract-We have examined Fe ⁄ Mn systematics of 34 type IIA chondrules in eight highly unequilibrated CO, CR, and ordinary chondrites using new data from this study and prior studies from our laboratory. Olivine grains from type IIA chondrules in CO chondrites and unequilibrated ordinary chondrites (UOC) have significantly different Fe ⁄ Mn ratios, with mean molar Fe ⁄ Mn = 99 and 44, respectively. Olivine analyses from both these chondrite groups show well-defined trends in Mn versus Fe (afu) and molar Fe ⁄ Mn versus Fe ⁄ Mg diagrams. In general, type IIA chondrules in CR chondrites have properties intermediate between those in UOC and CO chondrites. In most UOC and CR type IIA chondrules, the Fe ⁄ Mn ratio of olivine decreases during crystallization, whereas in CO chondrites the Fe ⁄ Mn ratio does not appear to change. It is difficult to interpret the observed Fe ⁄ Mn trends in terms of differing moderately volatile element depletions inherited from precursor materials. Instead, we suggest that significant differences in the abundances of silicates and sulfides ± metals in the precursor material, as well as open-system behavior during chondrule formation, were responsible for establishing the different Fe ⁄ Mn trends. Using Fe-Mn-Mg systematics, we are able to identify relict grains in type IIA chondrules, which could be derived from previous generations of chondrules, including chondrules from other chondrite groups, and possibly chondritic reservoirs that have not been sampled previously.

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Abstract-Siderophile elements have been used to constrain projectile compositions in terrestrial and lunar impact melt rocks. To obtain a better knowledge of compositional differences between potential chondritic projectile types, meteorite analyses of the elements Ru, Rh, Pd, Os, Ir, Pt, Cr, Co, Ni, and Au were gathered into a database. The presented compilation comprises 806 analyses of 278 chondrites including new ICP-MS analyses of Allende and two ordinary chondrites. Each data set was evaluated by comparing element ratios of meteorites from the same chondrite group. Characteristic element abundances and ratios were determined for each group. Features observed in the element abundance patterns can be linked directly to the presence of certain components, such as the abundance of refractory elements Os, Ir, and Ru correlating with the occurrence of refractory inclusions in CV, CO, CK, and CM chondrites. The refined characteristic element ratios appear to be representative not only for meteorites, but also for related asteroidal bodies. Chondrite element ratios were compared to previously published values from impact melt rocks of the Popigai and Morokweng impact structures confirming that an identification of the specific type of projectile (L and LL chondrite, respectively) is possible. The assessment for Morokweng is supported by the recent discovery of an LL chondrite fragment in the impact melt rocks. Ultimately, the database provides valuable information for understanding processes in the solar nebula as they are recorded in chondrites. A new type of complementarity between element patterns of CK and EH chondrites is suggested to be the result of condensation, redox, and transportation processes in the solar nebula.

Introduction:The electron microprobe has become an invaluable tool for determining bulk chemical compositions of different components of meteorites. Here, we are focusing on chondrules, which are small (up to mm-sized) igneous spherules in chondritic meteorites. A precise knowledge of bulk chondrule compositions is essential for constraining the chondrule-forming mechanism and for understanding the relationship between chondrules and the surrounding matrix [e.g., 1]. Even though, as Albee et al. [2] stated "most probe analysts recognize that large errors are involved" especially for coarse-grained samples, several scientists have used defocused beam analyses (DBA) to determine bulk chondrule compositions with or without various correction procedures [3][4][5][6][7]. On the other hand, when bulk chondrule compositions are determined by modal recombination analysis (MRA), minor elements tend to be less precise when accessory phases are ignored [8].We obtained a dataset of DBA and MRA for a chondrule from the CV3 chondrite Vigarano, in order to demonstrate how different the results can be. The presented work is supplementary to a previously published LPSC abstract [9], where detailed analytical conditions are given. Defocused beam analyses (DBA): 75 analyses with a beam diameter of 50 µm were obtained on a grid (100 µm apart), so that they covered the entire chondrule (Fig. 1a). The first big problem that becomes apparent when doing DBA is how to deal with analyses that do not have acceptable totals. Here, we have treated our analyses slightly differently than in [9]. High totals often correspond to mixed analyses (silicate + metal/sulfides) and the fact that Fe is present in two oxidation states (as Fe 2+ in silicates and as Fe 0 in metal). Instead of simply normalizing these analyses to 100 wt% [9], we corrected them by converting some of the FeO into Fe until the total converged to ~100 wt%. Low totals resulted from spots where cracks or holes are present. Analyses with totals between 90 and 97 wt% were normalized to 100 wt%. The bulk chondrule composition (Table 1, row A) was calculated by simple averaging (10 analyses were discarded). Oxide wt% were converted to element wt%, so that the data can be easily compared to the results obtained by MRA. Modal recombination analysis (MRA): Figure 1b shows a "phase image" of the chondrule, which was constructed in Adobe Photoshop based on element maps. It was used to determine the modal abundance of each phase. Our MRA data published in [9] were calculated with an equation given in [10], without taking the density of the different phases into account. Since this might be a commonly-made mistake, we show these results again (Table 1, row B). The data published here are slightly different from those published in [9], because veins with terrestrial alteration products (e.g., calcite) are now better taken into account. Finally, the bulk composition shown in Table 1, row C

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