Mineralogy and petrology of the CK chondrites Yamato-82104, Yamato-693 and a Carlisle Lakes-type chondrite Yamato-82002

概要

論文の詳細を見る
We have studied the mineralogy and petrology of three metamorphosed chondrites, Yamato (Y)-82104,Y-693,and Y-82002,which were previously classified as C5,C4 and C5,respectively. The results indicate that Y-82104 and Y-693 should be included with the CK carbonaceous chondrites. Y-82104 and Y-693 are remarkably similar in mineralogy and texture (e.g., virtually identical compositions of olivines, Fa 29.2±0.4vs. Fa 29.4±0.7,respectively). Thus, they are probably paired. The compositional homogeneity of olivine and pyroxene and degree of recrystallization of olivine and plagioclase are consistent with Y-82104 and Y-693 being petrologic type 5. Y-82002 differs from most CK chondrites in mineralogy and petrology, but is similar to Carlisle Lakes-type chondrites which were recently proposed to be a new grouplet of chondrites (A. E. RUBIN and G. W. KALLEMEYN, Geochim. Cosmochim., 53,3035,1989). We believe that Y-82002 is a member of this grouplet. Y-82002 was previously classified as petrologic type 5,but the relatively inhomogeneous compositions of olivine (e. g., Fa 35.1±5.1 for chondrules) and low degree of recrystallization of olivine and plagioclase suggest that Y-82002 should be classified as petrologic type 3.8-3.9.
国立極地研究所の論文