Institute of Geology and Mineralogy, Faculty of Science, Hiroshima University
抄録(英)
Ultramafic granulites in the East and West Ongul Islands area are grouped into two types, A and B. One of the fundamental criteria of the grouping is that type A does not yield plagioclase and type B does. Type A is characterized by the abundance of orthopyroxene and clinopyroxene and by the lack of plagioclase and garnet. It occasionally yields olivine. Type B is characterized by the presence of plagioclase and/or garnet and by the poverty in pyroxenes. In common cases, type A tends to occur as massive isolated blocks or pods in the surrounding gneisses, while type B as concordant sheets or layers showing a distinctly foliated structure. Between these two types, chemical characteristics of main constituent minerals such as orthopyroxene, clinopyroxene and hornblende are different from each other. Those in type A are comparatively more magnesian and less aluminous. Metamorphic temperature estimated from the pairs of orthopyroxene and clinopyroxene of both types is as high as around 800℃. Pressure condition is calculated based upon the associations of garnet, pyroxenes and plagioclase of type B to give the values around 7.5kb. The essential difference between the two types is inferred to reflect the difference in petrological characters of original rocks.
雑誌書誌ID
AA00733561
雑誌名
Memoirs of National Institute of Polar Research. Special issue
Short note on ultramafic granulites in the Ongul Islands area, East Antarctica
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概要
