愛媛県松山付近の高マグネシア安山岩に包有される超塩基性岩類の変形様式

概要

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Ultramafic inclusions were found in high magnesian andesite at Dogo, Matsuyama City, Ehime Prefecture, Southwest Japan. They are classified into two types, from the texture and chemical composition of minerals ; type-1 and type-2. Type-1 inclusion is harzburgite, characterized by the presence of Al-rich spinel. Type-2 inclusion is composed of dunite and harzburgite, with Cr-rich spinel. Olivine fabric patterns of the inclusions exhibit high concentration of X and Z axes, which differ from those of cumulate rocks. It seems that the textural development of the inclusions occurred through deformation process. Petrographical evidence supports this. Dislocation structure of olivine from the inclusion was examined. The dislocation density of olivines for type-2 inclusion falls into the range of 1×10^7 to 5×10^7cm^<-2> . The subgrain size of olivines from type-1 and type-2 inclusion has narrow range from 20 to 35μm. Considering the rate of stress-responce of dislocation density, subgrain size and grain size, it is concluded that type-1 inclusion deformed in nearly steady-state creep, whereas type-2 inclusion deformed in transient creep.
岡山理科大学の論文
1989-03-20