Sample processing and initial analysis techniques for Antarctic micrometeorites.

Based on our initial visual selection (IVS) criteria and low vacuum (LV)-SEM/EDS data, we successfully selected candidates of unmelted chondritic Antarctic micrometeorites (AMMs) from the unsorted sample set collected by Maurette's group in 1991. AEM data of some of the selected microparticles show that they are unmelted but probably dehydrated AMMs. An AMM candidate, 91-1-C4,contains ferroan (around Fo30) olivine grains which have planar channels parallel to (001). Their textures quite resemble those shown in the initial stage of iddingsite formation of olivine phenocrysts in terrestrial basalts. These findings indicate that some olivine crystals in AMMs can be altered even in the Antarctic environment.