A major change in magma sources in late Mesozoic active margin of the circum-Sea of Japan domain: Geochemical constraints from late Paleozoic to Paleogene mafic dykes in the Sergeevka belt,southern Primorye,Russia     

Victor P. Nechaev  Evgene V. Sklyarov  Yukio Isozaki  Nikolay N. Kruk  Alexey V. Travin  Yukiyasu Tsutsumi  Eugenia V. Nechaeva 《Island Arc》2021,30(1):e12426

More than 30 mafic dykes crop out in the Sergeevka belt in the coastal South Primorye, Far East Russia, of which geologic settings have been unclear for years. This study conducted major- and trace elements characterization, Sr–Nd isotope analyses, and Ar–Ar amphibole and U–Pb zircon datings for these rocks in order to identify their origin. The results demonstrated that all dykes are characterized by high Ba/Yb and low Nb/Y, Zr/Y, and Th/Yb ratios, which suggest their origin from arc melts derived from thin wedge mantle and shallow-dipping slab. These dykes are clearly separated into two distinct age/geochemistry suites; that is, the Paleogene and Early Cretaceous one with dolerites/basalts and adakitic rocks, and the Permian–Triassic one with high-Mg and high-Al gabbro-dolerite varieties. Their geochemistry suggests that the older suite was sourced from a primitive depleted MORB mantle (DMM)-type mantle, whereas the younger suite from an enriched mantle II (EM2)-type mantle domain. The transition in source type from DMM to EM2 occurred during the Jurassic-earliest Cretaceous time, probably by a strong influence of a mantle plume onto the long-continuing subduction-related magmatism. The plume influence reached the maximum when the unique meimechite-picrite complex formed in the region.  相似文献   

Motion of Mars: 1935–1976     

Yukio Niimi 《Celestial Mechanics and Dynamical Astronomy》1982,26(2):179-179

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Buffer Operation on Spatial Data with Limited Accuracy     

Yukio Sadahiro 《Transactions in GIS》2005,9(3):323-344

The quality of spatial data is limited by the accuracy of their sources such as paper maps and satellite images. It is also reduced by errors in map digitization and photo interpretation. Spatial operations performed on spatial data such as map overlay, buffer operations and spatial smoothing, do not always work correctly because their accuracy depends on the quality of spatial data. The present paper evaluates the accuracy of the buffer operation on a point and a line segment in relation to the positional accuracy of spatial data. Two quantitative measures are introduced to assess the accuracy of the buffer operation. Their explicit forms are derived for a point, and a condition is presented where the measures can be evaluated efficiently by numerical calculation. Applications provide empirical findings that deepen our understanding of the relationship between the accuracy of spatial data and that of the buffer operation.  相似文献   

Refined Early to Middle Miocene diatom biochronology for the middle- to high-latitude North Pacific     

Mahito  Watanabe  Yukio  Yanagisawa 《Island Arc》2005,14(2):91-101

Abstract   Refined numerical ages of the diatom biohorizons of the Early to Middle Miocene (11–18 Ma) period in the Neogene North Pacific are presented based on the direct correlation between biostratigraphy and magnetostratigraphy at Site 887 on the Patton–Murray Seamount in the northeastern Pacific. Sampling intervals of 0.02–0.04 my allowed the determination of the ages of the biohorizons to be more precise than previous studies. The secondary biohorizons established in the northwestern Pacific have been proven to be useful also in the northeastern Pacific, and are linked to magnetostratigraphy directly for the first time. The refined diatom biochronology established in this study will provide a vital basis for the study of the Neogene marine sediments of the middle- to high-latitude North Pacific, which rarely yield calcareous microfossils. Denticulopsis praedimorpha var. prima n. var. is described.  相似文献   

A computational approach for the analysis of changes in polygon distributions     

Yukio Sadahiro  Mitsuru Umemura 《Journal of Geographical Systems》2001,3(2):137-154

 This paper develops a computational method for analyzing changes in polygon distributions. Unmovable polygons that change discontinuously without explicit functional linkage information are discussed. Six types of primitive events are used to describe the change: 1) generation, 2) disappearance, 3) expansion, 4) shrinkage, 5) union, and 6) division. The change of polygon distributions is decomposed into a combination of these events. A computational procedure for deducing a set of events from polygon distributions of two times is proposed. The method is applied to the analysis of the spatial competition between the major and small chains of convenience stores in Tokyo, Japan. Some empirical findings are shown. Received: 3 August 2000 / Accepted: 6 February 2001  相似文献   

Number of Polygons Generated by Map Overlay: The Case of Convex Polygons     

Yukio Sadahiro 《Transactions in GIS》2001,5(4):345-353

This paper analyzes the number of polygons generated by map overlay. Overlay of maps yields a number of small polygons, and often causes problems in computation, handling, and storage of derived polygons. One method to deal with these problems is to estimate the number of derived polygons before executing overlay operation. To this end, a stochastic model is proposed by which the expected number of derived polygons is calculated. The results are summarized as follows: (1) the number of polygons generated by map overlay depends on the number of original polygons and their perimeters; (2) the number of derived polygons increases with the perimeters of original polygons; (3) McAlpine and Cook's (1971) earlier method underestimated the number of derived polygons; and (4) the number of polygons generated by the overlay of maps having the same lattice system is proportional to the square of the number of overlaid maps and the number of polygons on the map, and inversely proportional to the area-perimeter ratio of the unit cell.  相似文献   

Analysis of the effect of land use patterns on the anthropogetic energy discharged from air conditioning and hot water supply using a modified CSU mesoscale model   总被引：2，自引：0，他引：2  

Teruhisa Watanabe  Atsuyuki Okabe  Takeki Izumi  Yukio Sadahiro 《GeoJournal》2001,53(4):385-390

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Spectroscopic properties of Cr-doped melilite crystals     

Akiko Sugimoto  Yukio Nobe  Takafumi Yamazaki  Yutaka Anzai  Kiyoshi Yamagishi  Yusaburo Segawa  Humihiko Takei 《Physics and Chemistry of Minerals》1997,24(5):326-332

 Four kinds of Cr-droped melilite crystals, Ca₂MgSi₂O₇ (akermanite), CaAl₂SiO₇ (gehlenite), CaGa₂SiO₇ (Ga-gehlenite) and CaGa₂GeO₇ (GaGe-gehlenite), with different sizes of the sites for Cr ions to substitute, were grown in series, using both the CZ and FZ techniques. Although Cr⁴⁺ is regarded as a major species in melilites, the existence of Cr⁶⁺ in gehlenite is also suggested from the change in absorption spectra by annealing, and the dependence of distribution coefficient of Cr ions on growth atmosphere. Spectral peak shifts are not obvious if the host crystal field is altered in melilites, because the local environment of the sites for Cr ion is possibly changed by reforming the packing features of the host lattice. Received February 7, 1996 / Revised, accepted September 20, 1996  相似文献   

Anatomy and genesis of a subduction-related orogen: A new view of geotectonic subdivision and evolution of the Japanese Islands   总被引：8，自引：0，他引：8  

Yukio  Isozaki 《Island Arc》1996,5(3):289-320

Abstract The Japanese Islands represent a segment of a 450 million year old subduction-related orogen developed along the western Pacific convergent margin. The geotectonic subdivision of the Japanese Islands is newly revised on the basis of recent progress in the 1980s utilizing microfossil and chronometric mapping methods for ancient accretionary complexes and their high-P/T metamorphic equivalents. This new subdivision is based on accretion tectonics, and it contrasts strikingly with previous schemes based on‘geosyncline’tectonics, continent-continent collision-related tectonics, or terrane tectonics. Most of the geotectonic units in Japan are composed of Late Paleozoic to Cenozoic accretionary complexes and their high-PIT metamorphic equivalents, except for two units representing fragments of Precambrian cratons, which were detached from mainland Asia in the Tertiary. These ancient accretionary complexes are identified using the method of oceanic plate stratigraphy. The Japanese Islands are comprised of 12 geotectonic units, all noted in southwest Japan, five of which have along-arc equivalents in the Ryukyus. Northeast Japan has nine of these 12 geotectonic units, and East Hokkaido has three of these units. Recent field observations have shown that most of the primary geotectonic boundaries are demarcated by low-angle faults, and sometimes modified by secondary vertical normal and/or strike-slip faults. On the basis of these new observations, the tectonic evolution of the Japanese Islands is summarized in the following stages: (i) birth at a rifted Yangtze continental margin at ca 750–700 Ma; (ii) tectonic inversion from passive margin to active margin around 500 Ma; (iii) successive oceanic subduction beginning at 450 Ma and continuing to the present time; and (iv) isolation from mainland Asia by back-arc spreading at ca 20 Ma. In addition, a continent-continent collision occurred between the Yangtze and Sino-Korean cratons at 250 Ma during stage three. Five characteristic features of the 450 Ma subduction-related orogen are newly recognized here: (i) step-wise (not steady-state) growth of ancient accretionary complexes; (ii) subhorizontal piled nappe structure; (iii) tectonically downward-younging polarity; (iv) intermittent exhumation of high-P/T metamorphosed accretionary complex; and (v) microplate-induced modification. These features suggest that the subduction-related orogenic growth in Japan resulted from highly episodic processes. The episodic exhumation of high-P/T units and the formation of associated granitic batholith (i.e. formation of paired metamorphic belts) occurred approximately every 100 million years, and the timing of such orogenic culmination apparently coincides with episodic ridge subduction beneath Asia.  相似文献   

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Yukio Fujinawa 《Journal of Oceanography》1975,31(4):176-177

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