@article{oai:nipr.repo.nii.ac.jp:00010098,
 author = {Komatsu, Mutsumi and Mikouchi, Takashi and Miyamoto, Masamichi and Komatsu, Mutsumi and Mikouchi, Takashi and Miyamoto, Masamichi},
 issue = {1},
 journal = {Polar science, Polar science},
 month = {Jun},
 note = {Amoeboid olivine aggregates (AOAs) are composed of forsteritic olivine, Fe,Ni-metal, and Ca,Al-rich nodules consisting mainly of Al-diopside, spinel, and anorthite. Although the textures, shapes, and mineralogy of AOAs are consistent with their being aggregates of nebular condensates, some textures are in conflict with equilibrium condensation calculations, indicating that AOAs were not produced by a simple one-stage condensation. To examine the origin of the constituent minerals within AOAs and their textural relationships, we performed heating experiments using mineral mixtures analogous to those in AOAs. Isothermal and cooling experiments on forsterite + anorthite mixtures reveal that a high-Ca pyroxene phase forms via the incipient melting of the two minerals. Comparative studies of heating experiments performed using the mineralogy of AOAs suggest that Al-diopside in AOAs can be produced from a small degree of melting of forsterite and anorthite. The formation of Al-diopside in this way is consistent with the annealing textures observed in AOAs, and it may account for the discrepancy between the observed mineralogy of AOAs and the results of equilibrium condensation calculations, the occurrence of two types of diopside (Al,Ti-rich diopside and Al-diopside), and the variable Al_2O_3 content of Al-diopside., アメーボイド・オリビン・アグリゲイツ(AOA)は、炭素質コンドライトの主要構成物の一つである。AOAは、原始太陽系星雲ガスからの凝縮過程を経て形成されたと考えられているが、単純な平衡凝縮過程だけでは説明できない組織を有している。本研究において、AOAの構成鉱物を出発物質とした加熱実験を行ったところ、フォルステライトとアノーサイトの部分溶融により、高Ca輝石が形成された。この実験の結果から、AOA内においても高温下で、同様の反応が起こった可能性があることが示された。また、このような再加熱により、上記の平衡凝縮計算との差や、AOAに二種類の高Ca輝石が存在することも説明することが可能である。},
 pages = {31--55},
 title = {High-temperature annealing of amoeboid olivine aggregates: Heating experiments on olivine-anorthite mixtures},
 volume = {3},
 year = {2009}
}