Petrofabric analysis of a large microporphyritic chondrule in the Parnallee meteorite

SUMMARY. Olivine microphenocrysts in a large microporphyritic chondrule in the Parnallee chon-drite show a linear preferred orientation of the long (/3 = c) axes, which is thought o reflect flowage of a partly crystalline parent magma. The orientation pattern is somewhat disturbed by post-crystal-lization fracturing. THE origin of chondrules and chondrites remains in dispute in spite of intensive petrographic and chemical study during the last century. At one extreme, chondrules are currently interpreted as quenched roplets formed in the solar nebula either by condensation of gas (Wood, I963; Anders, I964; Blander and Katz, I967) or by fusion of dust (Whipple, I966). At the other, they are regarded as products of volcanic or impact processes on planetary bodies (Fredriksson, I963; Fredriksson and Ring-wood, I963; Ringwood, I966; Urey, I96I). There is general agreement that most or all chondrules crystallized from molten material: at issue is whether they were always independent droplets of roughly their present sizes or were drawn from larger masses of magma or solid rock. A decision on this point requires detailed study of many individual chondrules i