抄録
Our systematic study shows that ilmenite is always present in LL chondrites. Ilmenite is encountered in the chondrules and matrix. The MnO content of ilmenite in LL3.0-3.3 is lower than that in LL3.5-6. The low concentration of MnO in the former is due to crystallization from chondrules melts at high temperatures. On the other hand, ilmenite composition in LL3.5-6 reflects thermal metamorphism. Therefore, ilmenite is indicative of petrologic type. We also made the first measurements of the 53Mn-53Cr systematics of ilmenite in ordinary chondrites. The age for ilmenite in Y790256 (LL6) may be about 2 Ma older than angrites, although the excess 53Cr is not significant at 2 sigma errors.
