In this study we analyzed the chemical composition of hydrothermally altered dacite and basalt from the Kuroko mining area, northeastern Honshu, Japan, by REE (rare earth element). Features of rare earth element analyses include: (1) altered footwall dacite exhibits a negative Eu anomaly compared with fresh dacite, suggesting preferential removal of Eu2+ from the altered dacite via hydrothermal solutions, (2) altered hangingwall dacite and basalt and dacite and basalt adjacent to ore deposits exhibit positive Eu anomalies compared with fresh dacite and basalt, suggesting addition of Eu2+ from hydrothermal solutions, (3) LREE ratio (∑LREE/∑REE) from altered dacite of chlorite–sericite zone and K-feldspar zone show a negative relationship with δ18O, and La/Sm ratios show a positive correlation with the K2O index. These trends indicate the addition of light rare earth elements such as La to the altered dacite from hydrothermal solution and/or leaching of heavy rare earth elements such as Sm and Yb, (4) Principal component analysis (PCA) indicates that light rare earth elements enrichment is related to the formation of sericite zone near the Kuroko deposits but not to the formations of chlorite and K-feldspar zones, and (5) The correlations among REE features (LREE ratio, MREE ratio, HREE ratio, Eu/Eu?), δ18O and K2O index are not found for montmorillonite zone, mixed layer clay mineral zone and mordenite zone. Therefore, it is inferred that sericite, chlorite and K-feldspar alterations are related to the Kuroko and vein-type mineralization, but montmorillonite and mordenite alterations are not related to the mineralizations, and probably they formed at the post-mineralization stage. 相似文献
Summary A tensile fracture of about 1 m in length was created by indenting wedges in a block of granite, and the heights of the two
fracture surfaces were measured using a large, non-contact surface profile measurement system with a laser profilometer to
determine the aperture distribution of the fracture. Based on the measured data, the frequency characteristics of the asperity
heights, the initial aperture (the aperture when the surfaces are in contact at a single point), and the size effect on the
statistical properties were analyzed. The results can be summarized as follows:
1.
The relation between the power spectral density of the fracture surface and the spatial frequency shows linearity on a log–log
plot and thus the fracture surfaces can be assumed to be fractal object. On the other hand, the power spectral of the initial
aperture becomes almost constant for wavelengths greater than about 100 mm. Thus, the matedness between the two surfaces of
a fracture of 1 m monotonously increases with wavelength.
2.
The standard deviation of the initial aperture increases with fracture size until the fracture size is about 200 mm, beyond
which the standard deviation is almost independent of the fracture size. On the other hand, the mean initial aperture still
increases when the fracture size exceeds 200 mm, since the initial aperture depends on the minimum value of the aperture,
which decreases with the number of data points.
Authors’ address: Dr. Kiyotoshi Sakaguchi, Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aramaki-Aza-Aoba,
Aoba-ku, Sendai 980-8579, Japan 相似文献
At four stations in Tokyo Bay, pore water profiles of dissolved organic carbon (DOC), nitrogen (DON), phosphorus (DOP), and inorganic nutrients were determined at 3-month intervals over 6 years. Concentrations of dissolved organic matter (DOM) and nutrients were significantly higher in pore waters than in the overlying waters. Pore water DOC, DON, and DOP concentrations in the upper most sediment layer (0–1 cm) ranged from 246 to 888 μM, from 14.6 to 75.9 μM, and from 0.02 to 9.83 μM, respectively. Concentrations of DOM and nutrients in pore waters occasionally showed clear seasonal trends and were highest in the summer and lowest in the winter. The seasonal trends in the pore water DOM concentrations were coupled with trends in the overlying water temperature and dissolved oxygen concentration. Benthic effluxes of DON and DOP were low compared with those of inorganic nutrients, accounting for only 1.0 and 1.5 % of the total benthic effluxes of nitrogen and phosphorus, respectively; thus benthic DOM fluxes were quantitatively insignificant to the inorganic nutrient fluxes in Tokyo Bay. The DOM fluxes represented about 7, 3, and 10 % of the riverine discharge of DOC, DON, and DOP to Tokyo Bay, respectively. 相似文献
Three dimensional electric fields were measured at the altitude of about 27 km in the stratosphere over the Pacific Ocean about 200–400 km away from the Sanriku coast of Honsyu Island (L = 1·4) on 16–17 October 1973, which was magnetically disturbed. The average horizontal electric field thus measured is about 10 mV/m, and the electric field vectors made clockwise semidiurnal rotations rather than diurnal. Daily variation of this electric field was compared with data at L = 2·7–3·5 published by Mozer (1973) and was found to be very similar. This suggests that these electric fields are of common origin in the plasmasphere. From their mean daily variation it is estimated that the plasmaspheric convection is decreased in the night side and is increased in the day side by 200–300 m/sec, and there is an outward flow in the first half of the afternoon and an inward flow in the plasma bulge region of about 500 m/sec. 相似文献
The radial brightness distribution of the quiet Sun at 8.6 mm is synthesized from observations using a sixteen element east-west interferometer in Nagoya. The observed brightness is flat from the disk center to 0.8R. A slight darkening appeared between 0.8R and the limb. No evidence of the bright ring near the limb is found. The radio radius at 8.6 mm is 1.015±0.005R. In addition there exists a coronal component just outside the radio limb. 相似文献
We have determined the energetic and spatial characteristics of baroclinic and barotropic tidal semi-diurnal fluctuations using the current temperature and velocity data collected by 12 self-contained buoy stations (SCBS) near the shelf of the Republic of Guinea at depths ranging from 50 to 1000 m. Intensive baroclinic motion was observed to prevail near the bottom within the depth range 100–1000 m. The energy of long waves largely propagated from the bottom to the surface, whereas the energy of short waves was transferred in the opposite direction.Translated by V. Puchkin. 相似文献
The 2B/X2.8 double-ribbon flare of 30 March, 1982 is investigated using H, white light, X-rays, and microwaves. The X-ray burst seems to consist of two components, i.e., an impulsive component showing a long chain of peaks and a thermal component (T 2 × 107 K).In the early phase, the source images for the impulsive component were available simultaneously at soft (7–14 keV) and hard (20–40 keV) X-rays. Both sources are elongated along a neutral line. The core of the source for the hard X-rays is located at one end which seems to be a footpoint (or a leg) of a loop or arcade, while the core for the soft X-rays is located at the center of the elongated source which would be the center of the loop. The core for the hard X-rays shifted to this center in the main and later phase, accompanied by decrease in the source size in the later phase.A peak of one-directional intensity distribution at 35 GHz always lies on the core of the hard X-ray source, showing a shift of the position synchronous with the hard X-ray core. This may imply a common source for the radio waves and the hard X-rays.The source of the thermal component observed at the soft X-rays (7–14 keV) after the early phase covers a whole H patches. This may imply a physical relation between the thermal X-ray loops and the H brightening. 相似文献
It is well known that sea-salt aerosols in particulate matter (PM) react with acids such as H2SO4 and HNO3 during transportation and thereby lose chloride ions (Cl-loss). The PM and fog were sampled concurrently at different altitudes in the Hachimantai mountain range, northern Japan. The PM and fog sampled at different altitudes had nearly identical properties for the ion components. However, the PM was in a Cl-depleted state (more than 80% of all samples), but the fog water was not in so Cl-depleted state (less than 29%). As a result, it could be explained that this phenomenon caused because the fog droplets took up the gaseous state HCl other than sea-salt PM. After all Cl- in the fog water recovered and was rather rich compared with the sea-salt or the PM by the uptake of the gaseous state HCl. Moreover, it was found that for PMcoarse(2.5 < D < 10), 86% of the acid (H2SO4 and HNO3) was consumed for Cl-loss reactions and/or for dissolution of Ca and Mg in soil particles. 相似文献
The Tochiyama landslide is one of several complex, deep-seated and large-scale landslides occurring in the Hokuriku Province in central Japan. The landslide is about 2 km long and about 500–1100 m wide; it occupies an area of approximately 150 ha and has a maximum depth of 60 m. The slide developed on a dip-slope structure, and is divisible into three layers in ascending order: older landslide debris and avalanche deposits, younger debris-avalanche deposits, and talus. The landslide complex is still active. A triangulation point on the upper part of the landslide shifted downhill by 3.3 m from 1907 to 1983, indicating an average rate of 4.3 cm/y. In 1991, the average rate of movement on the sliding surface was also 4.3 cm/y as measured by an automatic system with inclinometers installed in borehole No. 1–2. The rate measured for borehole No. 1–3, located 380 m upslope from No. 1–2, was over twice that of No. 1–2 for the same period; it has since accelerated to about 19 cm/y. Thus current movements on the basal sliding surface are inhomogeneous; the head of the slide complex is increasing the horizontal granular pressures on the lower part of the slide block.
On the basis of dating of two tephra layers and14C dating of carbonized wood intercalated within the landslide body, two stages of slide movement have been distinguished. The earlier occurred between about 46,000 to 25,000 years ago, and the latter occurred since 1361 A.D. The following sequence of events is inferred. During the middle Pleistocene, intense tectonic movements occurred in the Hokuriku Province, and as a consequence dip-slopes were developed in the Tochiyama landslide area. Low-angle fault planes (possibly representing slump features) and fracture zones then developed within flysch deposits underlying the landslide area, causing a reduction in shear strength. The erosion base level was lowered during the Würm glacial age, and due to severe erosion and incision of stream valleys, the surface slope angle rapidly increased, and toe resistance decreased. This combination of causes led to the development of a deep-seated primary landslide. As a result of an accumulation of younger deposits, regional uplift and further local erosion, stability of parts of the region decreased and led to landslide activity of a second stage. Reactivated and locally accelerating creep movements occur today and may forewarn of a stage of reactivated, hazardous rapid sliding, such as occurred with the adjacent and analogous Maseguchi landslide in 1947. 相似文献