Chinese Journal of Polar Research (极地研究) 2013/25:4 PP.436-448
Chondrules are the main constituents of chondrites. There are 3 main kinds of classification schemes of chondrules currently, i.e., texture, FeO-SiO2 and M-FeO-CaO. The texture classification depends on texture and morphology highly but chemical composition unclosely. The FeO-SiO2 and M-FeO-CaO classification schemes introduce mineral chemical criteria onto traditional texture taxonomic scheme and provide further insight into the physical-chemical process occurring in the solar nebula. But the practical applications are too few for the latter two schemes. The chondrules in Kumtag 004 (L4, S4, W3) from the new desert meteorites enrichment region-Kumtag desert of Xinjiang have been classified based on the three classification schemes after observing structure and analyzing composition. Then we discuss the advantages and disadvantages of the FeO-SiO2 and M-FeO-CaO classification schemes and the application range. For the FeO-SiO2 taxonomic scheme that can be applied to porphyritic chondrules as well as non-porhyritic chondrules, we suggest that FeO=7.5% (wt%) is the boundary between type I and Ⅱ chondrules and so are 47% and 53%(SiO2, wt%) for type A, AB and B chondrules. A approximate partition is proposed for the type A1(FeO<1, CaO>1), A2(FeO≈1-3, CaO<0.5), A5(FeO≈11-14, CaO≈0.3-0.9) and B(FeO>3, CaO<0.5) chondrules for the M-FeO-CaO classification scheme based on the pyroxene (FeO and CaO, wt%).
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