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Besides many granitic xenoliths of volcanic rocks, their original granitic rocks and the host volcanic rocks ranging from basalt to andesite, all found in Southwest Japan, were petrographically examin...ed before the detailed studies of zircons in them were made. The xenoliths can be divided into five groups according to the degree of rock alteration. In the granitic xenoliths mafic minerals are most easily decomposed to produce mainly iron-ores and brown glass. The microperthitic texture of the original potash feldspar in the greater parts of the xenoliths disappeared and this mineral is readily resorbed after the mafic minerals. Plagioclase and quartz are more resistant to fusion: the former is commonly clouded to various extent with minute inclusions, and the latter is usually crackled, while vitrified plagioclase is apt to show fine mesh works of glass along its cleavages. Feldspar optics shows that potash feldspar and plagioclase in all the xenoliths are completely or incompletely converted to the high-temperature form. The observations described above may support the conclusion that the temperature attained by the granitic xenoliths in question should be between 500° and 573° in one example and above 500° to 700°and probably below about 900° in the others.続きを見る
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Introduction Acknowledgements Occurrence of grantic xenoliths Thin section petrography of rocks of grantic xenoliths Thin section petrograpy of grantic xenoliths Tenperatures attained by grantic xenoliths Summaty and conclusions References cited
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Mendeley出力
14_01_p039