| Abstract: | Abstract— A method is described for whole rock analyses of major elements in stone meteorites using the electron microprobe and requiring only powdering of the sample, most of which can be retrieved after analysis for additional analytical studies, such as instrument neutron activation analysis (INAA), radiochemical neutron activation analysis (RNAA) and O-isotopic analysis. Whole individual chondrules of > 1 mg can be analyzed. The method is especially attractive for meteorites in short supply or of great rarity. A total of 398 meteorites were analyzed by this method. The results compare favorably with wet chemical analyses. A study was made of seventeen ordinary chondrites to compare their whole rock (metal free) compositions with the averaged compositions of eleven to thirty-eight of their respective individual chondrules (a total of 374 chondrules). The oxide ratio Al2O3/CaO is generally lower in chondrules than in their respective chondrites, the disparity being larger for petrographic grade 5 than for grade 3. Ordinary chondrites are not simply the sum of their respective chondrules. Furthermore, correlations between CaO, Al2O3 and TiO2 are strong for chondrules in unequilibrated chondrites and nonexistent in equilibrated chondrites. Also H, L and LL chondrite groups have similar bulk compositions within their respective groups, in spite of the different proportions of chondrules, kinds of chondrules, chondrule debris, and matrix. All this brings into question the metamorphic classification in which high petrographic grades are the metamorphosed equivalents of low petrographic grades. |
