浅所貫入深成岩のCa角閃石の累帯構造(<特集II.>角閃石研究の現状と課題-地団研第37回総会造岩鉱物シンポジウム-)

概要

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Compositional zonings of amphiboles are reviewed and discussed on felsic plutonic rocks which were solidified at shallow place and under high oxygen fugacity condition, based on data from the literatures and additional analyses of amphiboles from the Koyama calcalkaline intrusion. Amphiboles characteristically zone from hornblende toward actinolite with decreasing Fe content. Very low A1^<IV> and Na contents of the amphiboles indicate that substitution of MgSi ⇄ Fe^<3+>Al^<IV> is most persistent. In many cases amphiboles display compositional gap between A1^<IV>=0.8 and 0.7, suggesting changes in crystallization condition during a late magmatic stage. Amphiboles with A1^<IV><0.6 in the Koyama intrusion crystallized or were reequilibrated under subsolidus condition. An important role of fluid phase is strongly suggested for amphibole crystallization at the late magmatic stage.
地学団体研究会の論文
1984-09-25