The R/V KAIREI of Japan Marine Science and Technology Center (JAMSTEC) has surveyed juncture of the Japan Trench and the Kuril Trench, focusing on geophysical investigations of the northern edge of the Pacific plate, including bathymetry, gravity, and total and three-component geomagnetics along MCS/OBS track lines and box survey lines during Leg KR00-04. The purposes of this study are: (1) to obtain geophysical and geological observations of subduction zones at the northern Japan Trench region; (2) to reveal a fine scale shape of subducted seamounts and its vicinity area from the view of sub-bottom topography, gravity, and magnetics; and (3) to understand the northern edge of the Pacific plate kinematically. Magnetic lineations aligned WSW-ENE directection can be clearly seen oceanward to landward slope of the Pacific plate. The location of Erimo Seamount and its vicinity area are strong geomagnetic intensity with 1000 nT of Peak ?Peak. We also investigate the compensation mechanism of subducting seamount using admittance functions.

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The Miocene volcanic activity in Hungary, the central part of the Carpatho-Pannonian Region, was remarkably heterogeneous in terms of eruption characteristics, structure, texture, mineral and chemical compositions of rock products, etc. Often, the corresponding complexes are classified as belonging to either an acidic, or a calc-alkaline type of volcanism, although the numerous spatial overlaps of the volcanic formations together with the published radiometric age and isotope data introduce uncertainties into any simple typification. In the given study, treated together all available, summing up to several hundred, major element chemical composition data determined in Miocene tuffs are analyzed with simple statistical methods. The major element composition of these tuffs reveals an essential univariate, bivariate and multivariate unimodality, as opposed to the statistical behavior of the corresponding effusives that have a well-known bimodal character. The tuffs have a significantly higher content of compositional water than the lavas. Part of the water in tuffs is of magmatic origin, part of it is due to hydration related to conditions after and/or during eruption. The distribution of Na is similar in both rock types, although a generally more intense surface weathering, leading to Na leaching, in tuffs is suggested. There is a discrepancy also in the potassium distributions which may incorporate a primary (i.e. related to the magmatic stage) difference, and traces of a potassium metasomatism having been able to better develop in some lavas. The bivariate distribution of Fe2O3 and FeO provides an estimate (being about 10%) for the maximum of total iron occurring in the primordial magmas of these rocks. The compositional unimodality of tuffs produced by the represented volcanisms (no matter how many types of them are assumed) suggests significant genetic relations.

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In recent years, it became easy to analyze the two dimensional data which covers a wide area using the various data with the progress of the GIS software and superior performance of the personal computer. As for the mineral resource exploration field, too, GIS and the program which customized this become used for the selection of the promising area, the selection of the drilling point using geological feature data, geophysical prospecting data, geochemical prospecting data, and so on. The application of the fuzzy set theory is thought as one of the ways of analyzing prospecting data. This method, at first, select known deposits theme and buffer theme applied the distance from exploration index. Buffer theme mean polygon set like tree rings made by constant distance from each exploration index, i.e. geology, deposit, geochemical, geophysical data and so on. Next, decide the membership function to every exploration index and to newly created all grid points, and outputs favorability mapping for mineral exploration. In this study, the fuzzy buffer program was created which can process a series of such processes of the analysis easily by customizing the macro language of GIS. The favorability mapping which is output by the created fuzzy buffer program was verified. As the object area, Hokuroku area, Akita Prefecture was taken up (31 km of east-west direction, 44km of north-south direction). In this area, a lot of Kuroko deposits were discovered, and gathered many kinds of prospecting data. Here, as the known deposit theme, 1km grid points within 1km from the ore bodies were set. As the buffer theme of exploration criteria, seven themes were used in this research, namely, K2bufs(the edge of submarine dacitic sequence and upper layer), K3bufs(upheaval circular structure in submarine dacitic sequence and upper layer), K6bufs(dacite/rhyolite dyke), K8bufs(andesite dyke), K10bufs(vein type deposits, hanging wall stratum is host rock), K12bufs(alteration index) and gradient of gravity, they showed effective criteria in the result of multiple regression analysis. The fuzzy set which is allocated with 1/exp function as a membership function, and the GAMMA operator was used to estimate fuzzy score. As a result, the favorability mapping got to have harmonized with the known deposit well with the multiple regression analysis, reflecting a deposit genesis having to do with learning after using only an effective prospecting index, not using an unnecessary prospecting index. As one of the evaluation methods of the favorability mapping result by the various analysis techniques, the ROC curve (receiver operating characteristic curve) was created. As a result, in case of the fuzzy set application, it is possible to estimate that 50% of ore bodies are discovered at 10% of prospecting area and that the discovery percentage exceeds 80% at 23.5% of prospecting area. It is expected that application of fuzzy set theory is available to discover ore bodies in Hokuroku area, and to do prospecting more efficiently

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