Petrology of chondrules in ALH-77015 (L3) chondrite

Chondrules in ALH-77015 (L3) chondrite were studied petrographically. Size and bulk chemical composition of about one hundred chondrules were investigated with relation to their texture. There seems to be no relation between the size and the texture, and the texture is mainly controlled by chemical composition, especially SiO_2,MgO and FeO contents. Another controlling factor, such as cooling rate, degree of supercooling or maximum temperature of heating, seems to be subordinate. Two types of olivine grains, different in the occurrence and mineralogy, are contained in some porphyritic chondrules. One is thought to be a relic crystal which had already existed before chondrules formation, representing secondary origin of chondrules. It further shows a relative low temperature of heating and a short duration of melting at the time of chondrule formation.