Chemical evolution in the solar nebula based on the chondrite matrix

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Optical/electron microscopy and Raman spectroscopy have been carried out about EH3 chondrites (Sahara 97096, 97121, 97158). There are a pyroxene chondrule surrounded by a fine-grained rim consisting of low-Ca pyroxene, plagioclase (glass), SiO-rich phases, Fe-Ni metal, and troilte. The chemical composition of the fine-grained rim is similar to CI-chondrite but different in some elements. This suggests that chemical fractionation in the solar nebula has occurred under the highly reduced condition. The fine-grained rim contains graphite-like matter showing variable Raman spectra, as found in IDPs that originate from comets. This indicates that the fine-grained rim in EH3 chondrites is composed of primitive and unequilibrated materials.