Fluorine contents of some hydrous minerals derived from upper mantle and lower crust

Fluorine contents have been determined in about forty samples of amphibole, mica and apatite in alkali basalt and kimberlite and their incorporated xenoliths. They show a wide variation ranging from 15,000 to 100 ppm, corresponding to about 40 to 0.2 per cent substitution of F for OH in hydroxyl site of hydrous minerals. Fluorine abundances in these minerals reflect those of their host magmas or rocks; Itinome-gata xenoliths are the lowest and South African kimberlites and their xenoliths are the highest. F/OH and also. D/H (Kuroda et al. 1975) ratios in coexisting phlogopite-potassic richterite from peridotite and mica nodules are thoughts to have formed under no simple equlibrium conditions.     

Seismological significance of the 1977–1978 eruptions and the magma intrusion process of usu volcano, Hokkaido

An earthquake swarm, and the major pumice eruptions in August 1977 which followed, marked the start of the dacitic doming activity of Usu volcano in southwestern Hokkaido, Japan. The sequence of magma intrusion processes was investigated in detail by means of seismological and other geophysical data. The distribution of the abundant hypocenters shows clearly an earthquake-free zone beneath the summit crater. The hypocenters migrated in a manner consistent with the development of the observed asymmetrical surface deformations, considered due to magma intrusion into this earthquake-free zone. The earthquake mechanism solutions are mostly of dip-slip type and are interpreted in terms of the doming deformations. The existence of earthquake families (earthquakes with similar waveforms) is the main cause of the peculiar occurrence of earthquakes in space, time and magnitude. The concept of scattered barriers of different sizes and strengths can explain well the distinct characteristics of the occurrence of the swarm, and the observed episodic deformations.     

Multivariate correlation analysis of suspended-sediment characteristics

Principal component analysis (PCA) was employed to investigate interrelationships among various characteristics of seawater and suspended sediments obtained from surface waters of two Asian marginal seas. On the basis of multivariate correlation analysis for the two marginal seas combined, three important factors were extracted and interpreted: (1) current-energy conditions, (2) the influence of rivers, and (3) biochemical conditions of seawater. A relationship between anisotropic mineral grains and combustible organic matter is suggested by the fact that suspended sediment, containing coarser anisotropic mineral grains, also contains larger amounts of combustible organic matter.     

Sex‐related differences in size,function and regeneration of the major cheliped in the hermit crab Pagurus filholi

Pagurus hermit crabs have a well‐developed right cheliped (major cheliped) and in some species the major cheliped of males is longer than that of females. This paper describes sex‐related differences in major cheliped length and regeneration pattern of the major cheliped in the hermit crab Pagurus filholi. We also examined the function of the major cheliped in male–male competition. Major cheliped length of males was longer than that of females in P. filholi. Males regenerated larger chelipeds than females at the first molt after experimentally induced autotomy. Body size growth in males of the regeneration group was less than that in intact males of the control group while there was no significant difference in body size growth of females between regeneration and control groups. Major cheliped length was included in the best model to explain the outcome of male–male competition and thus sexual selection appears to be a causative factor in the sex‐related difference of the major cheliped length. Sex‐related differences in the regeneration pattern may reflect differences in evolutionary pressures on males for large major chelipeds and females for large body size.     

Distribution of <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> in the southwestern Sea of Japan related to meandering of the Tsushima Warm Current

We investigated the horizontal distribution of Nemopilema nomurai medusae using a midwater trawl in the southwestern Sea of Japan from September to October of each year from 2006 to 2012. Numerous medusae of this species found in 2006, 2007, and 2009 were mainly distributed far (>40 km) from the mainland of Japan in the western part of the survey area, but were distributed in the stations closest (<25 km) to the mainland in the eastern part, particularly in 2006 and 2009. These distribution patterns were associated with the path of the second branch of the Tsushima Warm Current (TWC) that flows offshore to the west of Oki Islands and usually approaches the mainland of Japan to the east of Oki Islands. Differences in jellyfish distribution across the survey periods were related to the distribution of the second branch being associated with types, position and intensity of eddies in the eastern part of the survey area. Hence, the formations of eddies and consequent variation in the path of the TWC would be responsible for transporting medusae from offshore to near the mainland to the east of Oki Islands. Individuals with large bells accumulated in the northwestern part of the survey area, where a cyclonic eddy was present downstream of the third branch of the TWC. This variation in bell size distribution may be ascribed to differences in the physical and/or biological factors among the three branches of the TWC.     

Trans-Equatorial Loop System Arising from Coronal Hole Boundaries through Interactions between Active Regions and Coronal Holes

It is not clear how trans-equatorial loop systems (TLSs) are formed, although they have been observed often with Yohkoh/SXT. We focus here on a TLS that appeared on 27 May 1998. Yokoyama and Masuda (Solar Phys. 254, 285, 2009) proposed a new scenario for the formation mechanism of the TLS. In this scenario, they pointed out the importance of magnetic interaction between an active region and a coronal hole to make “strong-seed magnetic fields” before a transient (bright and short-lived) trans-equatorial loop was created. The main aims of this study are to verify the scenario and to make the TLS formation mechanism clear, based on observational data. Yohkoh/SXT images, SOHO/MDI magnetograph data, and Kitt Peak coronal-hole maps were mainly used for our analyses. We investigated the TLS in detail from the time that there were no signatures of the TLS to its clear appearance. The following results are obtained: i) an active region emerged in the vicinity of a coronal-hole boundary, ii) the coronal-hole boundary retreated during the period when the active region was developing, iii) temporal variations of soft X-ray intensities were roughly synchronized between the coronal-hole boundary and a trans-equatorial region, and iv) new closed loops were observed in soft X-rays clearly at the coronal-hole boundary. Since i), ii), iii), and iv) are just what we expect in the scenario of YM2009, the scenario found support. We conclude that the TLS was originating with large-scale magnetic fields of the coronal-hole boundary through magnetic reconnection between the active region and a coronal hole.     

Speciation of reduced C-O-H volatiles in coexisting fluids and silicate melts determined in-situ to ∼1.4 GPa and 800 °C

The structure of silicate melts in the system Na₂O·4SiO₂ saturated with reduced C-O-H volatile components and of coexisting silicate-saturated C-O-H solutions has been determined in a hydrothermal diamond anvil cell (HDAC) by using confocal microRaman and FTIR spectroscopy as structural probes. The experiments were conducted in-situ with the melt and fluid at high temperature (up to 800 °C) and pressure (up to 1435 MPa). Redox conditions in the HDAC were controlled with the reaction, Mo + H₂O = MoO₂ + H₂, which is slightly more reducing than the Fe + H₂O = FeO + H₂ buffer at 800 °C and less.The dominant species in the fluid are CH₄ + H₂O together with minor amounts of molecular H₂ and an undersaturated hydrocarbon species. In coexisting melt, CH₃ - groups linked to the silicate melt structure via Si-O-CH₃ bonding may dominate and possibly coexists with molecular CH₄. The abundance ratio of CH₃ - groups in melts relative to CH₄ in fluids increases from 0.01 to 0.07 between 500 and 800 °C. Carbon-bearing species in melts were not detected at temperatures and pressures below 400 °C and 730 MPa, respectively. A schematic solution mechanism is, Si-O-Si + CH₄?Si-O-CH₃+H-O-Si. This mechanism causes depolymerization of silicate melts. Solution of reduced (C-O-H) components will, therefore, affect melt properties in a manner resembling dissolved H₂O.     

Differences in abundance and distribution of Alexandrium cysts in Sendai Bay,northern Japan,before and after the tsunami caused by the Great East Japan Earthquake

The tsunami caused by the Great East Japan Earthquake on 11 March 2011 greatly influenced the coastal benthic environment on the northern Pacific coast of Japan. We used the direct count method to investigate changes in the abundance and distribution of Alexandrium (Alexandrium tamarense and Alexandrium catenella) cysts before and after the tsunami in Sendai Bay. Densities of Alexandrium cysts in sediments collected in summer 2011 ranged from 0 to 8,190 cysts cm^?3. In the western part of the bay, the density increased greatly after the tsunami, the highest density being approximately 10 times the density recorded in 2005. Molecular identification of single cysts with multiplex polymerase chain reaction (PCR) showed that Alexandrium tamarense dominated the cyst population in the southwestern part of the bay in 2011. Furthermore, accumulation of cysts on the surface sediment after disturbance of the sediment was confirmed by a laboratory experiment. The main factor causing the drastic changes in abundance and distribution of Alexandrium cysts after the earthquake was considered to be vertical and horizontal redistribution of the cysts in sediments after the tsunami.     

High-resolution observations of dissolved isoprene in surface seawater in the Southern Ocean during austral summer 2010–2011

We measured dissolved isoprene (2-methyl-1,3-butadiene; C₅H₈) concentrations in a broad area of the southern Indian Ocean and in the Indian sector of the Southern Ocean from 35°S to 64°S and from 37°E to 111°E during austral summer 2010–2011. Isoprene concentrations were continuously measured by use of a proton-transfer-reaction mass spectrometer combined with a bubbling-type equilibrator. Concentrations of isoprene and its emission flux throughout the study period ranged from 0.2 to 395 pmol L^?1 and from 181 to 313 nmol m^?2 day^?1, respectively, the averages being generally higher than those of previous studies. Although we found a significant linear positive relationship between isoprene and chlorophyll-a concentrations (r ² = 0.37, n = 36, P < 0.001), the correlation coefficient was lower than previously reported. In contrast, in the high-latitude area (>53°S) we identified a significant negative correlation (r ² = 0.59, n = 1263, P < 0.001) between isoprene and the temperature-normalized partial pressure of carbon dioxide (n-pCO₂), used as an indicator of net community production in this study. This suggests that residence times and factors controlling variations in isoprene and n-pCO₂ are similar within a physically stable water column.