Geoscientific research on the geological cross section down to upper mantle in the arc-trench system with backarc basin

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This research program is based on the geological and geophysical expedition for ocean floor basic geosciences using huge scientific Research Vessels(R/V).First year : Experimental equipments in laboratory and observational systems for cruise were prepared. On 27-28 February 2003, we held symposium on "Geology, petrology, geophysics and geotectonic on Philippine sea" as corporative symposium, Ocean Research Institute(ORI), University of Tokyo(UT). Presented papers were published in book(196 pages).Second year : Geological and geophysical survey were operated on ocean floor geosciences to investigate trench-arc-backarc system in southern and eastern Philippine sea using R/V Hakuho-maru(3987ton), ORI, UT, during 18days, November 2003. Geological and petrological analyzes on dredged rocks including mantle peridotite, gabbro, basalt, and etc, from southern Mariana trench inner-wall suggest that petrological MOHO-discontinuity and thrust were locating along the wall. Ocean Bottom Seismometer … More (OBS) observation indicate that main edifice of Haha-jima seamount, Ogasawara forearc is composed by serpentinized peridotites.Third year : Geological and geophysical survey was also performed on Haha-jima seamount using R/V Tansei-maru(610ton), ORI, UT, during 13 days, November 2004. Petrological analyzes on dredged rocks showed that ophiolite sequences were confirmed at summit area. Geological samples and geophysical data obtained from above mentioned two main research area were analyzed, compiled and organized.Systematic sampling on constituting igneous rocks to establish geological cross section in both huge steep escarpment and Haha-jima seamount have been done and those samples were precisely analyzed by geological and petrological methods. Geophysical observations were also performed in these area. These geological and geophysical data were combined together so effectively that more accurate geological cross section than previous one including upper mantle can be proposed, then tectonics and petrological evolution in Philippine Sea can be solved. We had additional seminar on "Comparative studies on mantle structure and magma genesis between Philippine sea bedrocks and northeastern Japanese arc" on 7-8 March 2005, (Book coming soon). Less