OIKAWA Jun Earthquake Research Institute, University of Tokyo, 地震研究所, 助手 (40262084)
YASUDA Atsushi Earthquake Research Institute, University of Tokyo, 地震研究所, 助手 (70222354)
UTO Kozo Division of Geochemistry, Geological Survey of Japan, 地殻化学部, 主任研究官
YAMAOKA Koshun Faculty of Science, Nagoya University, 理学部, 助教授 (70183118)
NOHDA Susumu Faculty of General Education, Kyoto-Sangyo University, 教養部, 教授 (30065841)
TATSUMI Yoshiyuki Dept. Earth and Planet. Sci., Kyoto University, 総合人間学部, 助教授 (40171722)
KOYAGUCHI Takehiro Earthquake Research Institute, University of Tokyo, 地震研究所, 助教授 (80178384)
NAKADA Setsuya Earthquake Research Institute, University of Tokyo, 地震研究所, 助教授 (60128056)
FUJII Toshitsugu Earthquake Research Institute, University of Tokyo, 地震研究所, 教授 (00092320)
IDA Yoshiaki Earthquake Research Institute, University of Tokyo, 地震研究所, 教授 (30013535)
(1) Before we started the preliminary survey of the Reunion and Mauritius Island in 1994, we had visited the scientists of the IPGP (Institut de Physique du Globe de Paris) and got sufficient information directly on the sites of rocks which we wanted to collect and others. Further, we surveyed the Reunion Island from the air by a helicopter. Through the survey in 1994 and 1995, we could collect almost all kinds of samples which we want to get from the Reunion, Mauritius and Rodrigues Islands. They cover samples which range in space and time and include basalts with olivine phenocrysts and ultramafic nodules.
(2) Three of our group surveyed the Rodrigues Island in 1995 and found that the geology in this island is different between the eastern and western parts and the center of volcanic activity seems to have moved from the west to the east. The magmas do not seem to have been originated from the ridge system.
(3) Through the cooperative works with the scientists of the IPGP,as a volcanophysical study, we investigated the coda Q and found that it depends on the frequency of seismic waves. The coda Q around the Piton de la Fournaise volcano has been found to be identical with those of the island are and collisional regions. The time-sequence analysis has revealed that the rhythm of volcanic eruption for the Piton de la Fournase volcano and Mt. Fuji is controlled by a simpler system than those of Izu-Oshima and Miyake-jima volcanoes.
(4) For collected samples, thin sections were prepared and petrological, mineralogical, chemical and isotope analyzes including K-Ar dating are undertaken. After we accumulate such data, we will discuss the characteristics and origin of the Reunion hotspot.