Carbon materials in Antarctic and nonAntarctic carbonaceous chondrites: high-resolution transmission electron microscopy

摘要

Carbon materials from eight Antarctic carbonaceous chondrites (CM2, CO3, and CV3 types) and two nonAntarctic carbonaceous chondrites (CM2 and CV3 types) were studied using a high-resolution transmission electron microscope (HRTEM). Nanodiamonds and "carbonaceous globules" were found in seven of the Antarctic chondrites and one nonAntarctic CM2 chondrite. These results suggest that nanodiamonds and carbonaceous globules are common in carbonaceous chondrites. The finding of carbonaceous globules in the meteorites that experienced post-hydration high temperature thermal metamorphism suggests that they are resistant to thermal metamorphism. Well-crystallized graphite was mainly found in the CV3- and CO3-type chondrites, whereas poorly crystallized graphite was mainly found in the CM2-type chondrites. The CM2-type chondrites also contain characteristic carbon structures that are similar to tetrahedral carbon onions and multilayered fullerene. In this study, we discuss the origin of these types of carbon material.