KINOSHITA Hajimu Faculty of Science,Chiba University, 理学部, 教授 (10110347)
WAKITA Hiroshi Faculty o Science,University of Tokyo, 理学部地殻化学実験施設, 助教授 (40011689)
YAMANO Makoto Earthquake Research Institute,University of Tokyo, 地震研究所, 助手 (60191368)
FUJISAWA Hideyuki Earthquake Research Institute,University of Tokyo, 地震研究所, 助手 (50012927)
HAMANO Yozo Earthquake Research Institute,University of Tokyo, 地震研究所, 助教授 (90011709)
The main objective of the project was to obtain sufficient observational constraints on theoretical models to explain the pattern of heat flow distribution in trench-arc-backarc systems: namely the zonal arrangement of trenchward low heat flow and backarcward high heat flow zones. 1. We made a detailed study on the nature of the transition between the low and high heat flow zones, through developing a new technique for utilizing shallow holes. It was found that the transition takes place sharply between the aseismic and the volcanic fronts. 2. Extremely high heat flow and vigorous hydrothermal activities, similar those on mid-oceanic ridges, were discovered in the Okinawa and Mariana troughs testifying to the similarity between ocean floor spreading and backarc spreading processes. Such activities were sighted by deep submersibles also. 3. Some exceptions to the characteristic pattern of heat flow were also investigated, e.g. high heat flow at the bottom of the Nankai Trough where a young seafioor plate is subducting. Fof such studies, a new technique of hest flow estimation using the information on gas-hydrate layering was also used. 4. Contribution of heat generated in the crust in Japan has been estimated by measuring the contents of radioactive elements in rocks of possible deep crustal origin exposed in Hidaka mountains. Based on these and ohter measurements, made in such areas as Peru, Japan-Kurile and Yap Trenches, Japan Sea and Central Japan, distributions of temperature and Moho heat flow under arcs have been estimated. Some modelling investigation was made also on the thermal process associated with the collision between Eurasia and India to understand the genesis of granites and inverted metamorphic zones in the Himalayas. For the future work, it is highly desirable that the shallow sea areas, such as the East China Sea, be investigated geothermally more fully, because of both their geodynamic and economic importances.