著者

佐藤 博明

出版者

特定非営利活動法人日本火山学会

雑誌

火山. 第2集 (ISSN:04534360)

巻号頁・発行日

vol.30, pp.S173-S188, 1986-03-31

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Recent progress of the study of volcanoes in oceanic areas is reviewed. Major advance of the study has been brought about through the development of the following lines of researches; (1) narrow-beam echo sounding investigation with the aid of precise navigation systems to determine detailed sea bottom topography. (2) deep sea drilling for the determination of stratigraphy of oceanic basement. (3) direct observation and sampling of oceanic basement by submersibles. (4) development of isotope systematics such as Sr-Nd-Pb and He-Ar. (5) increase of accuracy as well as production rate of routine analyses of volcanic rocks; i.e. petrography, mineralogy, major and trace element compositions. Precise high-pressure phase equilibrium studies also afforded important constraints on the modelling of magma genesis in oceanic areas. Geological, petrological and geochemical characteristics of the volcanoes in oceanic areas are described according to the following classification scheme; [A] Monogenetic volcano (a) Oceanic ridge volcano, (b) Back-arc basin volcano, [B] Polygenetic volcano (c) Seamount near oceanic ridge, (d) Seamount near spreading center of back-arc basin, (e) Hot spot seamount, (f) Abyssal plateau, (g) Oceanic island arc volcano. Genetic models of these volcanoes are discussed, and it is shown that the mantle diapir model of SAKUYAMA (1983) can be applied to polygenetic volcanoes in oceanic areas. Generation and uprise of mantle diapir (or blob), and intrusion of mantle diapir into lithosphere may determine the essential features of polygenetic volcanoes; i.e. volume, duration of activity, evolutional history, major and trace element compositions, and isotopic ratios.