Studies on the origin of inclusions and chondrules in meteorites based on isotopic microanalyzes

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In this project, I conducted microanalyzes of oxygen (O) isotopes, magnesium (Mg) isotopes and rare earth elements (REE) using secondary ion mass spectrometry (SIMS) on refractory inclusions (CAIs) and chondrules in primitive meteorites and obtained important information on their origin and formation conditions. (1) I studied an inclusion from a CV chondrite and found large vatiations in oxygen isotopes in anorthite grains. I discussed the cause for such isotopic heterogeneity. (2) I studied rim of CAIs using Mg, O and REE analyzes. It was found that Mg isotopes in CAI rims are not fractionated, suggesting that the rims formed not by evaporation, but by condensation from a hot gas. (3) I conducted O, Mg and REE analyzes on an ultra-refractory nodule found in a fine-grained inclusion from the Allende meteorite. I discussed high temperature processes and gas-dust separation in the early solar nebula. (4) I conducted O and REE analyzes on CAIs found in most primitive ordinary chondrites and enstatite chondrites and found similarities between them and those in carbonaceous chondrites, which suggests a common origin for CAIs. (5) I studied O isotopes in FeO-rich and FeO-poor olivine grains in chondrules. I found similarities in their O isotopes in spite of the difference in the redox condition during their formation.