Deep mantle processes and the dynamic mechanism of magmatism in the Japan Sea Basin are important processes that have not been studied in detail.In this paper,systematic evaluation of basalt samples from the ocean dri...Deep mantle processes and the dynamic mechanism of magmatism in the Japan Sea Basin are important processes that have not been studied in detail.In this paper,systematic evaluation of basalt samples from the ocean drilling program Site 794 in the Japan Sea was performed,which included petrography,whole-rock major-and trace-element analysis,Sr-Nd-Pb isotopic composition,and electron microprobe analysis of plagioclase and clinopyroxene.These basalts belong to the tholeiitic series with porphyritic texture and massive Ca-rich plagioclase,clinopyroxene,and minor olivine phenocrysts.The basalts are characterized as flat rare earth elements and high-field-strength elements with remarkably low ratios of(La/Yb)N(0.75-2.51),significant positive anomalies of Ba,Sr,and Rb and no Eu anomaly(dEn=0.99-1.36).The samples showed relatively high 87Sr/86Sr(0.70425-0.70522),207pb/204pb(15.511-15.610),and 208pb/204pb(38.064-38.557)values and a low 143Nd/144Nd ratio(0.51271-0.51295).The basalts from Site 794 can be divided into upper,middle,and lower volcanic rocks(UVR,MVR,and LVR)on the basis of their stratigraphic level.The MVR was geochemically derived from the depleted mantle,whereas the UVR and LVR originated from a nondepleted and relatively enriched mantle source with contributions from subducted Pacific plate fluid and sediments.Use of geothermobarometers indicates that the crystallization pressure for the UVR and LVR(6.25-11.19 kbar)was significantly higher than that of the MVR(3.48-5.84 kbar).The UVR and LVR may have been derived from the low-degree(5%-10%)partial melting of spinel lherzolite,while the MVR originated from a shallower mantle source with a high degree(10%-20%)of partial melting.In addition,the geochemical characteristics of the samples are consistent with a younger age(13-17 Ma)and the depleted composition of the MVR and an older age(17-23 Ma)and slightly enriched composition of the UVR and LVR.Therefore,temporal changes in the mantle source from old and enriched to young and depleted and subsequently to old and nondepleted may have been associated with progressive lithospheric extension and thinning,as well as at least two episodes of diverse asthenospheric upwelling and pull-apart tectonic motion in the Yamato Basin.展开更多
The first social experiment program in Japan to reduce domestic wastewater pollutant discharge by ＂soft interventions＂ in households has been conducted in the Yamato-gawa River drainage area since 2005. The Yamato-g...The first social experiment program in Japan to reduce domestic wastewater pollutant discharge by ＂soft interventions＂ in households has been conducted in the Yamato-gawa River drainage area since 2005. The Yamato-gawa River has been listed as one of the worst water quality rivers in Japan because of the larger annual average BOD. ＂Hard interventions＂ including deployment of wastewater treatment facilities and artificial installation of natural purification facilities in the river has been conducted in these years to improve river water quality. At the first Yamato-gawa River social experiment program （YR-SEP） in March 2005, BOD at the monitoring point near the river mouth decreased about 6% during the Program. Natural purification effect along the river was evaluated in this article with one-dimensional water quality model for the six river sections. Larger biological oxygen consumption rate, kb, was estimated in the sections with artificially installed natural purification facilities. The effect of ＂soft interventions＂ in households in the YR-SEP was estimated as 25% BOD decrease in the nearest monitoring point to the river mouth, when all the households participate in the Program and BOD discharge reduction rate with ＂soft interventions＂ in households was 40%.展开更多
A study of tsunami events in the East （Japan） Sea using continuous Galerkin finite element model, aiming at reproducing tsunami waves generated by underwater earthquakes in 1983 and 1993 respectively has been perfor...A study of tsunami events in the East （Japan） Sea using continuous Galerkin finite element model, aiming at reproducing tsunami waves generated by underwater earthquakes in 1983 and 1993 respectively has been performed focusing on the geographic extent of a topographic feature in the East （Japan） Sea. Numerical models can be the proper tools to study the combined effects of realistic topography. Subsequently, using the FEM based two-dimensional model we have simulated the smoothed and flattened topographic effects by removal of Yamato Rise and seamounts for the cases of tthe 1983 Central region earthquake tsunami and the 1993 southwestern Hokkaido earthquake tsunami. The results have shown that there will be higher tsunamis along the eastern coasts of Korea in general except some areas, like Sokcho with removal of topographic highs, thus providing complicated bottom topography of the East （Japan） Sea as effective tsunami energy scattering.展开更多
基金supported by the National Natural Science Foundation of China(Grant code:41476034,41272369,40802038,41320104006,41302102 and 15CX05007A)
文摘Deep mantle processes and the dynamic mechanism of magmatism in the Japan Sea Basin are important processes that have not been studied in detail.In this paper,systematic evaluation of basalt samples from the ocean drilling program Site 794 in the Japan Sea was performed,which included petrography,whole-rock major-and trace-element analysis,Sr-Nd-Pb isotopic composition,and electron microprobe analysis of plagioclase and clinopyroxene.These basalts belong to the tholeiitic series with porphyritic texture and massive Ca-rich plagioclase,clinopyroxene,and minor olivine phenocrysts.The basalts are characterized as flat rare earth elements and high-field-strength elements with remarkably low ratios of(La/Yb)N(0.75-2.51),significant positive anomalies of Ba,Sr,and Rb and no Eu anomaly(dEn=0.99-1.36).The samples showed relatively high 87Sr/86Sr(0.70425-0.70522),207pb/204pb(15.511-15.610),and 208pb/204pb(38.064-38.557)values and a low 143Nd/144Nd ratio(0.51271-0.51295).The basalts from Site 794 can be divided into upper,middle,and lower volcanic rocks(UVR,MVR,and LVR)on the basis of their stratigraphic level.The MVR was geochemically derived from the depleted mantle,whereas the UVR and LVR originated from a nondepleted and relatively enriched mantle source with contributions from subducted Pacific plate fluid and sediments.Use of geothermobarometers indicates that the crystallization pressure for the UVR and LVR(6.25-11.19 kbar)was significantly higher than that of the MVR(3.48-5.84 kbar).The UVR and LVR may have been derived from the low-degree(5%-10%)partial melting of spinel lherzolite,while the MVR originated from a shallower mantle source with a high degree(10%-20%)of partial melting.In addition,the geochemical characteristics of the samples are consistent with a younger age(13-17 Ma)and the depleted composition of the MVR and an older age(17-23 Ma)and slightly enriched composition of the UVR and LVR.Therefore,temporal changes in the mantle source from old and enriched to young and depleted and subsequently to old and nondepleted may have been associated with progressive lithospheric extension and thinning,as well as at least two episodes of diverse asthenospheric upwelling and pull-apart tectonic motion in the Yamato Basin.
基金Financial support for the research was provided by the Osaka Bay Wide Area Marine Environment Foundation in JFY 2008
文摘The first social experiment program in Japan to reduce domestic wastewater pollutant discharge by ＂soft interventions＂ in households has been conducted in the Yamato-gawa River drainage area since 2005. The Yamato-gawa River has been listed as one of the worst water quality rivers in Japan because of the larger annual average BOD. ＂Hard interventions＂ including deployment of wastewater treatment facilities and artificial installation of natural purification facilities in the river has been conducted in these years to improve river water quality. At the first Yamato-gawa River social experiment program （YR-SEP） in March 2005, BOD at the monitoring point near the river mouth decreased about 6% during the Program. Natural purification effect along the river was evaluated in this article with one-dimensional water quality model for the six river sections. Larger biological oxygen consumption rate, kb, was estimated in the sections with artificially installed natural purification facilities. The effect of ＂soft interventions＂ in households in the YR-SEP was estimated as 25% BOD decrease in the nearest monitoring point to the river mouth, when all the households participate in the Program and BOD discharge reduction rate with ＂soft interventions＂ in households was 40%.
基金The work was financially supported by the Korean Ministry of Land,Transport and Maritime AffairsINTAS(Grant No.06-1000013-9236)
文摘A study of tsunami events in the East （Japan） Sea using continuous Galerkin finite element model, aiming at reproducing tsunami waves generated by underwater earthquakes in 1983 and 1993 respectively has been performed focusing on the geographic extent of a topographic feature in the East （Japan） Sea. Numerical models can be the proper tools to study the combined effects of realistic topography. Subsequently, using the FEM based two-dimensional model we have simulated the smoothed and flattened topographic effects by removal of Yamato Rise and seamounts for the cases of tthe 1983 Central region earthquake tsunami and the 1993 southwestern Hokkaido earthquake tsunami. The results have shown that there will be higher tsunamis along the eastern coasts of Korea in general except some areas, like Sokcho with removal of topographic highs, thus providing complicated bottom topography of the East （Japan） Sea as effective tsunami energy scattering.
