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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Acid digestion and alkali fusion were applied to sample preparation of granitic rocks for the rare earth elements (REE) analysis by inductively coupled plasma mass spectrometry (ICP-MS). Granitic rock samples were decomposed by conventional rock-dissolution techniques, and the residues were fused with the mixture of Na₂CO₃ and H₃BO₄. The fusion ensured complete dissolution of acid-resistant minerals. Appropriate amounts of major elements were added to the REE calibration standard solution for matrix matching. The conditions of the instrument were adjusted to minimize the formation of the oxide molecular ions. Fourteen REE in three standard samples of granitic rocks were determined successfully.

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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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