Experimental study of the alteration process of labradorite in acid hydrothermal solutions

Labradorite was altered artificially by HC1 solution ranging from M = 1 to M = 0.003 at 245 and 230°C. The products of alteration were examined by X-ray diffraction, electron microscopy, electron diffraction, infrared spectroscopy and the electron microprobe and the solution was analyzed chemically.Amorphous silica only was formed in solutions with M_HCl = 1 and M_HCl = 0.3. In a solution with M_HCl = 0.2, amorphous silica was initially formed, later dissolved and replaced by kaolinite. A mixture of microcrystalline boehmite and amorphous aluminosilicate was formed, altering to kaolinite in solutions with M_HCl = 0.1 and 0.3. Small amounts of kaolinite were initially formed but the alteration soon stopped in solution with M_HCl = 0.003. Relationships between the alteration processes and pH of the solutions can be roughly explained by using solubility diagrams assuming the congruent dissolution of labradorite and precipitation of the products in partial equilibrium. However, these assumptions are not valid with strongly acid solutions.The rate of dissolution of labradorite is controlled not only by its surface area, but also by the diffusion of matter through the layer of alteration products.     

Chromite-bearing spessartites from Kasuga-mura,Japan, and their bearing on possible mantle origin andesite

An unusual association of chromite and hornblende was found in the spessartites of andesite composition, occurring as a dike swarm associated with a Cretaceous granite batholith. The spessartites are largely porphyritic with phenocrysts of either hornblende or augite. One dike, comprising a finegrained spessartite, exhibits distinct chilled selvages of aphanitic facies. The chromites in the fine-grained and augite-spessartites are significantly higher in Cr/ (Cr+Al) than those occurring rarely as inclusions in the phenocrystic hornblendes in the hornblende spessartite, although both are similar in Mg/ (Mg+Fe), Fe₂O₃, and TiO₂. The phenocrystic hornblendes are titaniferous pargasite with high Mg/ (Mg+Fe), and differ in their higher octahedral Al from the groundmass hornblendes including those in the fine-grained spessartite. The crystallization sequence in the phenocrystic hornblende-bearing spessartites is Al-rich chromite, phenocrystic hornblende, and plagioclase without pyroxene, suggesting a high water content in the magma and the start of the crystallization at relatively high pressures. The finegrained spessartite from which the porphyritic spessartites have been derived by fractionation of dominant mafic minerals, has the high Mg-value and Cr content equivalent to those in primitive, undifferentiated basalts, although still andesitic in SiO₂ content. Chemically similar magnesian andesites, although uncommon, found in some orogenic calc-alkalic suites may represent a magma composition in equilibrium with mantle peridotite under the condition of high water pressures.     

Anomalous thermal expansion in spinel MgAl2O4

The accurate measurement of thermal expansion in spinel MgAl₂O₄ over a temperature range between 30° C and 900° C has revealed an anomalous behaviour indicating a possible presence of a second order phase transition at 660° C.     

A study of the morphology of winter sprites in the Hokuriku area of Japan in relation to cloud charge height

Continuous observations of sprites in the Hokuriku area of Japan were performed from two optical sites during the three winter periods. The purpose of this observation is to study the major effect in the appearance of sprites and in determining the morphology of sprites (columns or carrots). Detailed analysis is performed based on the estimation of the height of ?10 °C at the time of sprite occurrence. When the height of ?10 °C is lower than 1800 m, the occurrence of sprites is infrequent, and the dominant shape is column. Then when it is increased (1800–3000 m), a new situation takes place, namely the occurrence of sprites is very enhanced and more spectacular shapes like carrots tend to be frequently observed in addition to column sprites. These sprite characteristics are first compared with those of parent lightning in the Hokuriku area and with our latest computer simulations on sprite initiation.     

Relationship between Salinity and Nutrients in the Subsurface Layer in the Suruga Bay

We investigated the water structure and nutrient distribution in the Suruga Bay from April 2000 to July 2002, especially the Offshore Water, which occupies a large part of the bay. The maximum salinity in the upper 200 m varied between 34.49 and 34.71, indicating a temporal change in the influence of Kuroshio Water on the Offshore Water. Seasonal variation in nutrient concentrations was largest from surface to 50 m. On the other hand, the variance in nutrient concentrations within each season was largest in the subsurface layer of 100–300 m in spring, summer and fall. In the Offshore Water, the change of nutrients was negatively correlated with that of salinity in each season. This suggests that an increasing intrusion of saline water brings about a lower nutrient concentration in the Offshore Water. Likewise, negative correlations were observed between the change of the maximum salinity and chlorophyll a (Δ [chl.a-int])/nutrients integrated in the upper 200 m. Δ[chl.a-int] was significantly correlated with the changes of nitrate and phosphorus, but there were no significant correlations between Δ[chl.a-int] and the change of silicate. These results suggest that the concentrations of chlorophyll a and nutrients in the Offshore Water were decreased due to the increasing intrusion of Kuroshio Water. The Offshore Water is likely to be related to the regulation of primary production by nitrate.     

Physical parameters identification for full-scale ten-story reinforced concrete building with degrading tri-linear model by modal iterative error correction method

To assess the post-earthquake seismic safety of buildings, it is crucial to predict seismic response, and it is necessary to set the appropriate physical parameters of the response analysis model. Numerous methods have been proposed to identify physical parameters. However, most of them are limited to linear systems, and previous researches on nonlinear systems have difficulties in practical applications. In this paper, a nonlinear response analysis model is identified for a full-scale ten-story reinforced concrete building with the degrading tri-linear stiffness model by the modal iterative error correction (MIEC) method, and the accuracy of this technique is discussed by comparing with the shaking table test.     

Origin of calcium in aerosols over the western North Pacific

Weekly aerosol samples were collected from March 1981 to June 1983 at the six stations in the western North Pacific region and analyzed for Ca and Na. By coupling data with those previously reported for Al (Tsunogai et al., 1985), the following results and conclusion have been obtained. There was a positive correlation between the atmospheric concentration of Al and the concentration of nonsea salt Ca (nssCa). The nssCa/Al ratios from the six stations, however, considerably varied (from 0.84±0.36 to 3.00±1.91), and the ratios were usally larger than those of the crustal average or of usual soil in Japan. The Ca/Al ratios of Asian desert soil and loess vary from 0.52 to 1.29, which are similar to the nssCa/Al ratios of aerosols in the surface air over the western North Pacific region except at Onna, Okinawa. The exception may be due to a local effect of coral. These results suggest that a large part of nonsea salt Ca in the surface air over the western North Pacific is derived from arid regions in Asia and that the nssCa/Al ratio in aerosol varies with that of the source material.     

Formation process of pyrite polyframboid based on the heavy-metal analysis by micro-PIXE

Pyrite framboid in sedimentary rocks could be concerned with arsenic contamination in groundwater of acidic environment and has been studied for the formation process of its unique morphology. However, not much has been discussed about the formation process based on the heavy-metal distribution in pyrite framboids and their aggregates. To reveal the formation process of pyrite framboids and their aggregates, mudstone from the Late Cretaceous Hakobuchi Group, central Hokkaido, Japan, are investigated for mode, petrographical, mineralogical, and micro-PIXE (particle-induced X-ray emission) analysis in this study. Spherical and sub-spherical pyrite framboids observed in polyframboids can be divided into two types based on the diameter of framboids (D) and the average diameter of microcrystals (d) within framboids: type 1, ranging from 2 to 9 μm and from 0.4 to 0.9 μm, respectively, and type 2, ranging from 8 to 50 μm and from 0.5 to 1.8 μm, respectively. Based on the quantitative traverse analyses and 2-D elemental mapping results by micro-PIXE, heterogeneities in the concentrations of heavy metals within the analyzed aggregations of pyrite are exhibited. On the basis of the As and Pb zoning patterns, the time range and chronological stages of pyrite-aggregation growth are revealed.     

Morphodynamics of a bedrock‐alluvial meander bend that incises as it migrates outward: approximate solution of permanent form

In meandering rivers cut into bedrock, erosion across a channel cross‐section can be strongly asymmetric. At a meander apex, deep undercutting of the outer bank can result in the formation of a hanging cliff (which may drive hillslope failure), whereas the inner bank adjoins a slip‐off slope that connects to the hillslope itself. Here we propose a physically‐based model for predicting channel planform migration and incision, point bar and slip‐off slope formation, bedrock abrasion, the spatial distribution of alluvial cover, and adaptation of channel width in a mixed bedrock‐alluvial channel. We simplify the analysis by considering a numerical model of steady, uniform bend flow satisfying cyclic boundary conditions. Thus in our analysis, ‘sediment supply’, i.e. the total volume of alluvium in the system, is conserved. In our numerical simulations, the migration rate of the outer bank is a specified parameter. Our simulations demonstrate the existence of an approximate state of dynamic equilibrium corresponding to a near‐solution of permanent form in which a bend of constant curvature, width, cross‐sectional shape and alluvial cover distribution migrates diagonally downward at constant speed, leaving a bedrock equivalent of a point bar on the inside of the bend. Channel width is set internally by the processes of migration and incision. We find that equilibrium width increases with increasing sediment supply, but is insensitive to outer bank migration rate. The slope of the bedrock point bar varies inversely with both outer bank migration rate and sediment supply. Although the migration rate of the outer bank is externally imposed here, we discuss a model modification that would allow lateral side‐wall abrasion to be treated in a manner similar to the process of bedrock incision. Copyright © 2016 John Wiley & Sons, Ltd.     

Metaproteomic characterization of dissolved organic matter in coastal seawater

We performed a comprehensive metaproteomic analysis of the dissolved organic matter (DOM) in Japanese coastal waters using liquid chromatography–tandem mass spectrometry and demonstrated that these proteomes were characterized by proteins with various functions, including metabolic enzymes, membranes, and photosynthetic proteins. The protein sources included cyanobacteria, heterotrophic bacteria, and eukaryotic phytoplankton. Most of the components were similar among samples and also similar to pelagic components. We also observed differences in the compositions of the microbial communities of origin among the different dissolved protein samples and differences in the relative abundance of specific dissolved protein types (e.g., cytoskeletal proteins), possibly indicating potential dynamics in the coastal DOM pool.