Opaque Minerals in LL3.0–6 Chondrites I: Mineralogy of Ti‐oxides and 53Mn‐53Cr Systematics of Ilmenite

Abstract  We conducted a systematic study of oxide minerals in LL3.0–6 chondrites, and found ilmenite, rutile, perovskite and an unknown Al‐Ti‐Zr‐oxide. Ilmenite is low in abundance, but is present in the chondrules and matrix of all the samples that we studied. 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) is determined to be about 2 Ma older than angrites. This may represent the metamorphic age of the LL chondrites.