Petrology of the Yamato-74191 Chondrite

The chondrules in the Yamato-74191 meteorite (L3) are classified into seven groups by their SiO_2 contents and texture. The most common group (P III) shows intimate compositional relations between bulk composition of chondrules and olivines in them. The olivines in magnesian chondrules show wide compositional zoning from magnesian core to ferrous rim, whereas the olivines in ferrous chondrules are relatively homogeneous and have the same composition of ferrous rim olivines in the magnesian chondrules. This compositional relation may be explained by gradual increase and subsequent sudden decrease in the degree of oxidation state of silicate melt in the course of their crystallization