The isotope geochemical study for Iceland is reviewed. Iceland yields not only tholeiitic basalts but also tholeiitic andesites or rhyolites. Many geochemical studies were done to decipher the origin of the felsic volcanic rock which constitutes about 10% of the Icelandic crust. However, the origin was not clear. To solve this problem, the combination of Sr, Nd, Pb, He and O isotope tracers with U-Th disequilibrium has been attempted, and the involvement of the Icelandic hydrothermally altered crust into the source of the felsic rock is infered. In near future, application of new Li and B tracers will constrain the origin of the felsic rock in more detail.

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花崗岩質岩の希土類元素を正確かつ迅速にICP-MSによって定量する方法を検討した。試料を酸分解し，硝酸で溶解した後に，難溶性鉱物の分解を完全にするために残査を炭酸ナトリウムとホウ酸で融解し，合わせて測定溶液とした。検量線には，火成岩の主成分元素の組成を有する標準液を使用した。装置の調整により，干渉となる酸化物イオンの形成を抑えた。花崗岩質岩の標準試料3種の分析を行なって，良好な結果を得た。

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We have investigated the distribution and properties of the ground surface deformations, which were caused by the Hyogoken-nanbu earthquake, in the southeastern area of the Rokko Mountains, eastern part of Kobe city in Japan. The landforms of the study area are characterized by foot of Rokko Mountains formed by the weathered granitic rocks. The Otuki fault in this area is running parallel to the mountain foot from NE to SW. The ground surface deformations appear to be concentrated along the Otuki fault. Many mountain slope failures were collapsed on the Otuki fault. The reason for these slope failures distribution are thought to be strong ground motion by Hyogoken-nanbu earthquake. The upper parts of the mountain slope failures have broken by tension fractures of NE-SW.

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