Comparative Study of CV3 Carbonaceous Chondrites Allende and Bali Using Micro-Raman Spectroscopy and SEM/EDS

The birth of the solar system (over 4 billion years) is speculated to have happened from a nebula, swirling and compacting in localized regions to eventually form the Sun and planets. This complex process consists of numerous changes and intermediary steps, yet to be fully understood. Carbonaceous chondritic meteorites are relics of that process and therefore have potential to reveal information about the formation history. Several theories have been formulated linking their composition to planet formation. This study focusses on two carbonaceous chondritic specimens, Allende and Bali, both of the group CV and petrologic type 3. CV meteorites are abundant in inclusions (e.g. chondrules), which are considered the oldest objects to have formed in the solar system. Samples were studied using micro-Raman spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS). Chondrules were identified in the Allende sample, while Bali had several irregular inclusions and small crystals. These other inclusions were refractory inclusions rich in Ca and Al. Elements common to both were: O, Si, Fe, Mg, C and S. Ni, Ca and Al were also present but varied in relative percentage weight in each sample. Bali had several Fe-Ni spots, while no such spots were identified in Allende. S-rims were seen around inclusions in both, as was the Fe/Mg complementarity between matrix and inclusion. Minerals found in both were graphitic carbon and Mg-rich olivine. Allende also contained pyroxene and quartz; while Bali had larnite, magnetite and awaruite. Information obtained about the parent bodies of these samples includes their peak metamorphic temperatures and extent of secondary alterations (post-accretion). Allende was found to be more metamorphosed than Bali. Possible implications from the obtained results have been discussed in the light of planet formation models, such as that the formation of the inclusions and surrounding matrix could have taken place in the same local nebular region. Overall, the findings ...