Ameboidalne oliwinowe agregaty w chondrytach zwyczajnych
Amoeboid Olivine Aggregates in ordinary chondrites
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An amoeboid olivine aggregates (AOA) are the refractory end-member of a family of fine-grained inclusions. They consist of masses of fine-grained (generally forsteritic) olivine crystals with other phases dispersed in between. The AOA are important components of carbonaceous chondrite and have been reported only from the unequilibrated Semarkona LL3.0 ordinary chondrite and examined by author equilibrated Sahara 02500 ordinary chondrite. The AOA’s are thought to represent solar-nebula condensates that experienced high-temperature annealing, but largely escaped melting. An amoeboid olivine aggregate found in the equilibrated ordinary Sahara 02500 chondrite has experienced weak planetary metamorphism resulting in equilibration and recrystallization of fine-grained olivine and albitic feldspar. The aggregate contains several fine-grained inclusions consisting of recrystallised fayalitic olivine, feldspar and minor amounts of metal, diopside, chromite, and apatite.
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