Opaque Minerals in LL3.0-6 Chondrites I: Mineralogy of Ti-oxides and ^(53)Mn-^(53)Cr Systematics of Ilmenite  

作　　者：KIMURA Makoto SUGIURA Naoji NAKAJIMA Haruna Michael K.WEISBERG 

机构地区：[1]Faculty of Science Ibaraki University, Mito 310-8512, Japan,Department of Earth and Planetary Science University of Tokyo, Tokyo 113-0033, Japan,Faculty of Science Ibaraki University, Mito 310-8512, Japan,Department of Physical Sciences Kingsborough College of the City University of New York,Brooklyn, NY 11235 Department of Earth and Planetary Sciences, American Museum of Natural History,New York, NY10024, USA.

出　　处：《Acta Geologica Sinica(English Edition)》2004年第5期1082-1089,共8页地质学报（英文版）

摘　　要：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.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.

关 键 词：CHONDRITE ILMENITE Mn-Cr isotopes 

分 类 号：P185.8[天文地球—天文学]