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1.
Chemical compositions of schlieren in basalt flows are compared with those of the host rocks for tracing the fractionation trends of basalt magmas under extrusive conditions. In the Warner high-alumina basalt of California and in the tholeiite of Hawaii and Japan, total iron increases markedly from the host rock to the schlieren whileSiO 2 is nearly constant. In the high-alumina basalt of Huzi Volcano and in the tholeiite near Catania, Italy, total iron is nearly constant during fractionation whileSiO 2 increases. In basalts of the hypersthenic rock series or calc-alkali rock series from California, total iron is also nearly constant whileSiO 2 increases. The difference in fractionation trend in these flows is attributable to the difference of the state of oxidation of iron in the original magmas. Oxygen partial pressure of the magmas would not be maintained constant during the fractionation of extrusive bodies.  相似文献   
2.
Climate is simulated for reference and mitigation emissions scenarios from Integrated Assessment Models using the Bern2.5CC carbon cycle–climate model. Mitigation options encompass all major radiative forcing agents. Temperature change is attributed to forcings using an impulse–response substitute of Bern2.5CC. The contribution of CO2 to global warming increases over the century in all scenarios. Non-CO2 mitigation measures add to the abatement of global warming. The share of mitigation carried by CO2, however, increases when radiative forcing targets are lowered, and increases after 2000 in all mitigation scenarios. Thus, non-CO2 mitigation is limited and net CO2 emissions must eventually subside. Mitigation rapidly reduces the sulfate aerosol loading and associated cooling, partly masking Greenhouse Gas mitigation over the coming decades. A profound effect of mitigation on CO2 concentration, radiative forcing, temperatures and the rate of climate change emerges in the second half of the century.  相似文献   
3.
4.
Three petrographic provinces can be recognized in the Cenozoic volcanic fields of Japan and surrounding areas. A province of a tholeiite series lies on the Pacific side of the Japanese Islands and includes the Izu Islands, whereas that of an alkali rock series occupies the Japan Sea side of the Islands with a narrow offshoot extending across central Honsyū (Honshū) and a continuation westward to Korea and Manchuria. A province of a calc-alkali rock series is superposed on the two provinces and occupies the greater part of the Japanese Islands exclusive of the Izu Islands and the islands in the Japan Sea southwest of Honsyū and north of Kyūsyū (Kyūshū). The boundary lines between the tholeiite and alkali provinces are located very closely to those between the areas where earthquakes occur at depths shallower than about 200 km and those for deeper ones. It is suggested that the parental tholeiite magma is produced by partial melting of the periodotite layer at depths shallower than 200 km. In the Izu Islands, except Nii-zima(Nii-jima) and Kōzu-sima(Kōzu-shima) close to Honsyū, the magma erupts to the surface without assimilating granitic material because the granitic layer is absent, resulting in volcanoes made up exclusively of the tholeiite series. The parental alkali olivine basalt magma is produced by partial melting of the peridotite layer at depths greater than 200 km. In the Japan Sea region, Korea, and Manchuria, it erupts to the surface without assimilating the granitic material, although it passes through a thick granitic layer, resulting in volcanoes made up exclusively of the alkali series. However, in the Cenozoic orogenic belt of the Japanese Islands, both types of parental magma assimilate granitic material during passage to the surface and erupt to form volcanoes of the calc-alkali series.  相似文献   
5.
The study deals with the comparison of corrosion forms in differently soluble rocks from different climatic regions, namely forms of the naked karst (lapies), depressions, and corrosive plains. The far-reaching morphographic conformity of corresponding forms permits some general conclusions:
  1. The forms in question have the same genesis, there is no casual convergence of forms. It would be convenient to term them as forms of the salt-, gypsum-, and carbonate karst. There is no justification for a fundamental distinction between the “karstification” of limestone and the “leaching” of gypsum and salt.
  2. The different liability to karstification (Karstgunst) of rocks can be compensated by a different liability to karstification due to climatic factors.
  3. Similarly the other factors of karstification vary gradually; they add up or compensate each other. A classification of climatic-morphological karst provinces seems to be possible only by means of analysis and balance of the single factors and their effects.
  相似文献   
6.
It has been often observed that black mud recently formed and accumulated in slip planes that are closely associated with a progressing landslide in Japan. Mössbauer spectroscopy revealed that the composition of Fe species in the sliding mud is different from those in the debris rock and bedrock. The sliding mud contains more ferrous iron species, which indicates a relatively stronger reducing condition within the sliding zone than within the host rocks. In addition, the composition of Fe species, the total Fe and the volume of sliding mud also change with landslide development. Therefore, detailed Fe speciation in landslide profiles can be a useful approach to understanding the progress of a landslide and may also predict future sliding as well.  相似文献   
7.
After the phreatic eruption in 1982–83, volcanic activities at Kusatsu–Shirane volcano had been decreasing and reached a minimum in 1990, had turned to a temporal rise in activity up to 1994 and then decreased again at least up to 1997. During this low-activity period we observed a relatively short (≤ 1 y) cyclic variation in polythionates (PT) in the Yugama lake water. Spectral power density analysis of the PT time-series by an autoregressive (maximum entropy spectral estimation, MESE) method indicates that the major frequency in the PT variations is 1.0 y− 1 and the minor is 2–3 y− 1 (1.0 and 0.3–0.5 y in periodicity, respectively). Annual variations in the lake temperature are ruled out for explaining these periodicities. We attribute these cyclic variations to a cyclic magnification-reduction in meteoric-water injection into a hydrothermal regime where volcanic gases from cooling magma bodies at depth and cooler oxidized groundwater come into contact with each other. This interaction may result in a periodical change in the composition and flux of SO2 and H2S gases being discharged into the lake and forming PT. From a phase deviation (2–3 months) in the cycles between the annual precipitation, including snowmelt, and the PT time-series, we estimated the maximal depth of a hydrothermal reservoir beneath the lake assuming a vertical hydraulic conductivity (5 × 10− 3 cm/s) of the volcanic detritus around the summit hydrothermal system. Chloride in the lake water reached a maximum 1.5 years faster than PT. This is most likely due to a gradual elevation of the potentiometric front of a concentrated sublimnic solution in the hydrothermal reservoir. Variations of dissolved SO2 and H2S in the lake water were not consistent with those of the fumarolic gases on the north flank of the volcano. This fact together with additional observations strongly suggests that these fumaroles may have the same origin but are chemically modified by a subsurface aquifer. The PT monitoring at active crater lakes during a quiescent period can provide insight into the annual expansions and reductions of a volcano-hosted hydrothermal reservoir.  相似文献   
8.
We present recent results of the observations of giant molecular clouds in nearby galaxies with the Nobeyama 45 m telescope and Millimeter Array. We give some brief comments about observations of GMCs in nearby galaxies with ALMA.  相似文献   
9.
Origin of andesite and its bearing on the Island arc structure   总被引:1,自引:0,他引:1  
The hypothesis that andesite magmas originate from basalt magmas through fractionation is supported for the following reasons: 1) A close association of andesite and dacite with basalt in many volcanoes and a complete gradation in chemistry and mineralogy throughout this suite. 2) Formation of andesite magmas from basalt magmas by differentiation in situ of some intrusive and extrusive bodies. 3) Agreement between the calculated compositions of solid materials to be subtracted from basalt magmas to yield andesite magmas and the observed mineralogy of phenocrysts in these rocks. 4) Higher alkali contents in andesite and dacite associated with high-alumina basalt than in those associated with tholeiite. 5) A complete gradation from the high iron concentration trend of basalt magma fractionation (Skaergaard) to the low or noniron concentration trend (the calc-alkali series) which can be ascribed to the difference of the stage of magnetite crystallization. 6) Similarity between the orogenic rock suite and plateau basalts in the preferential eruption of magmas of middle fractionation stage, givin rise to the great volume of andesite in the orogenic belts and iron-rich basalt in the plateau lavas. Petrological and seismic refraction studies suggest that a great volume of gabbroic materials are present in the lower crust underneath the volcanic belts as a complementary material for the andesite lavas. The island arc structure would develop by repeated eruption of andesite on the surface and by thickening of the oceanic crust underneath the arc due to the addition of gabbroic materials. The suitable portion of the lower crust may be subjected to partial melting to produce granitic magma in the later stage of development of the arc, successively changing it to a part of the adjacent continent.  相似文献   
10.
On the south-eastern edge of Russia, the chemical composition of rainwater is controlled by sea salts, terrestrial material, as well as volcanic (Kuril islands volcanic area) and anthropogenic emissions, mostly in the southern part of the area. The predominant major ions of the Primorye, Sakhalin and the Kuril Islands rainwaters were respectively HCO3–SO42−, Ca–Na, and of Cl–Na. Concentration of trace elements changes within 1–2 orders of magnitude but some difference in the distribution of the elements between continental and island rainwater is found. The concentration of the chemical elements in the particulate fraction varies from < 10% to 90% of the total concentration (dissolved + particulate) with the following distribution: Tl, Na, Ca, Sr, Zn, Cd (< 10%)–Be, Th, Bi, Rb, U, K, Sc (10–20%)–Cu, Mn, Mg, Mo, Se, Ba, Ni, As, Ag, Cs, Co, Y, Ga, V (20–50%)–Sb, Pb, Ge, Cr, Fe, Al (50–90%).The concentration of elements of the particulate fraction of the rainwater usually is significantly different from concentrations in the crust, including both higher and lower concentrations. The terrestrial contribution to dissolved elements was evaluated and follows the decreasing order: Fe > K, Mg, Ca > Ba, Sr > Na (65–1%). Close order was found for total (dissolved and solid) concentrations. Sea salt contribution to dissolved element concentration in the rainwater decrease in the following order: Cl, Mg > K, SO4 > Ca > HCO3, Ba, Fe (78–0.1%). Calculation of anthropogenic and volcanic inputs for two ions (Cl and SO42−) shows that anthropogenic inputs for the Vladivostok and Yuzno-Sakhalinsk cities can be evaluated as 15–20% of Cl and up to 80–90% of SO42−. Volcanic components in the Kuril Islands, where anthropogenic inputs are absent, can reach up to 76% of SO42− and 36% of Cl.  相似文献   
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