Experiments on the Element Distribution between the Granodiorite JG-1a and 2M NaCl Hydrothermal Solution at Temperatures of 300 to 800°C and a Pressure of 1 kb

Abstract. The distribution of Na, K, Ca, Mg, Mn and Fe between the granodiorite JG-la, one of the geochemical standard rocks, and 2M NaCl aqueous solution was experimentally determined at temperatures of 300 to 800C and a pressure of 1 kb using standard cold seal-type pressure vessels. The solid run products melted partially at 800C. Only K shows a significantly different behavior from the experiments using the basalt JB-la (Uchida and Tsutsui, 2000) due to the presence of ortho-clase in the JG-la. The transition elements tend to be preferably partitioned into the aqueous chloride solutions with increasing temperature. At 800C and 1 kb, the Fe concentration of the aqueous chloride solutions reached up to 5,000 ppm, and the Mn concentration up to 350 ppm. The distribution coefficient, K_{D, i} = C_{i, sol}/C_i, rock, is in the order of Na>K>Mn>Ca> Fe>Mg at 300C, but changed in the order of Mn>N>K>Fe>Ca>Mg at 800C. The distribution coefficients of the divalent cations for the JG-la are higher than those for the JB-1a. The distribution coefficient of the transition elements, Fe and Mn, increases significantly with increasing temperature. The thermodynamic analysis for aqueous speciation revealed that this is attributable to the formation of the tri-chloro complexes of the transition elements at higher temperatures.     

Pb-Sr isotopic evidence for contribution of deep crustal fluid to the Hishikari epithermal gold deposit, southwestern Japan

The gold-bearing quartz-adularia veins of the world-class Hishikari mine in southwestern Japan occur in a geological regime where the rocks of the upper to middle crust are simple and their chemical and Sr-Nd-Pb isotopic compositions are well studied. Detailed comparison of Pb and Sr isotopic data of the Hishikari veins with those of all possible source materials demonstrates that metals in the veins were essentially derived from a mixture of magmatic fluid with a deep crustal fluid that originated near the boundary between the Shimanto middle crust and the underlying subcontinental crustal materials. We propose that the release of the deep crustal fluid was triggered by intrusion of the Shishimano rhyodacite magma related to timing of the mineralization. This fluid mixture carried metals to the brittle upper crust along fissures created by extensional stress forming the ore deposits. Although the deep crustal fluid has not been paid much attention, it may be distributed over a large scale in the deep crust from the continent to the arc system and play an important role in the genesis of magmatic-hydrothermal ore deposits and in the generation of flow-induced deep tremor.     

The 1989 submarine eruption off eastern Izu Peninsula,Japan: ejecta and eruption mechanisms

The submarine eruption of a new small knoll, which was named Teishi knoll, off eastern Izu Peninsula behind the Izu-Mariana arc occurred in the evening of 13 July 1989. This is the first historic eruption of the Higashi-Izu monogenetic volcano group. The eruption of 13 July followed an earthquake swarm near Ito city starting on 30 June. There were subsequent volcanic tremors on 11 and 12 July, and the formation of the Teishi knoll on the 100 m deep insular shelf 4 km northeast of Ito city. There were five submarine explosions, which were characterized by intermittent domelike bulges of water and black tephra-jets, which occurred within 10 min on 13 July. Ejecta of the eruption was small in volume and composed of highly crystalline basalt scoria, highly vesiculated pumice, and lithic material. Petrographical features suggest that the pumice was produced by vesiculation of reheated wet felsic tuff of an older formation. The Teishi knoll, before the eruption, was a circular dome, 450 m across and 25 m high, with steep sides and a flat summit. Considerations of submarine topographic change indicate the knoll was raised by sill-like intrusion of 10⁶ m³ of magma beneath a 30 m thick sediment blanket. This shallow intrusion is assumed to have started on 11 July when volcanic tremors were observed for the first time, but there was no indications of violent interaction between wet host sediments and intruding magma. The submarine eruption of 13 July appears to have been Friggered by a major lowering of the magma-column. The basalt scoria, having crystal-contents of more than 60%, is assumed to be derived from the cooled plastic margin of the shallow intrusive body. However, glassy scoria, which would indicate the interaction between hot fluidal magma and external water, was not observed. A scenario for the 1989 submarine eruption is as follows. When rapid subsidence of the hot interior of the intrusive magma occurred, reduced pressure caused the implosion of cooled plastic magma, adjacent pressurized, hot host material, and wet sediment. The mixing of these materials triggered the vigorous vapor explosions.     

Temporal and spatial variability of chlorophyll concentrations in the Bering Sea using empirical orthogonal function (EOF) analysis of remote sensing data

Seasonal and interannual variability of surface chlorophyll concentration in the Bering Sea was examined using Empirical Orthogonal Function (EOF) analysis of data obtained by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) from 1998 to 2002. The analysis of normalized monthly fields (removing temporal and spatial monthly means) shows that different temporal and spatial patterns are evident in the eastern and western Bering Sea during the spring bloom period. The first EOF mode explains 30% of the variability and shows how the eastern shelf break region and the western Bering Sea are out of phase during the spring bloom. The second EOF mode (17.6%) indicates a pattern involving the eastern shelf break region and the Kamchatka Basin. This strong east–west signal is linked by both surface winds and light. EOF modes of wind-speed anomalies, derived from Special Sensor Microwave Imager (SSM/I), and photosynthetically active radiance (PAR) from SeaWiFS, show a similar dipole feature where the east–west pattern is related to the position and strength of the Aleutian Low pressure system. In years when the Aleutian Low shifts from west to east, weaker wind stress facilitates the development of stratification resulting in a strong spring bloom in the western Bering Sea. The variability of spring chlorophyll has a strong connection with variability in atmospheric forcing in the Bering Sea.     

Distribution of glycerol dialkyl glycerol tetraethers, alkenones and polyunsaturated fatty acids in suspended particulate organic matter in the East China Sea

We investigated the spatial distribution of glycerol dialkyl glycerol tetraethers (GDGTs), alkenones, and polyunsaturated fatty acids in particulate organic matter collected at four sites along a depth transect from the continental shelf to the Okinawa Trough in the East China Sea during the spring bloom in 2008. The maximum alkenone concentration appeared in the top 25?m at all sites and the $ U_{37}^{{{\text{K}}'}} $ values were consistent with in situ water temperatures in the depth interval, suggesting that the alkenones were produced mainly in surface water. At the slope and shelf sites, GDGTs in the water column showed a concentration maximum at 74?C99?m depth, and the $ {\text{TEX}}_{86}^{\text{H}} $ agreed with in situ water temperatures, suggesting the in situ production of GDGTs in the depth interval. The low-salinity surface water above 20?m depth was characterized by low GDGT concentrations and low $ {\text{TEX}}_{86}^{\text{L}} $ -based temperatures, suggesting either the production of GDGTs in winter season or the lateral advection of GDGTs by an eastward current. At the slope and Okinawa Trough sites, TEX₈₆-based temperatures were nearly constant in the water column deeper than 300?m and corresponded to temperatures at the surface and near-surface waters rather than in situ temperatures. This observation is consistent with a hypothesis that Thaumarchaeota cells produced in surface waters are delivered to deeper water and also indicates that the residence time of suspended GDGTs in the deep-water column is large enough to mix the GDGTs produced in different seasons.     

Differential geometric approach to the stress aspect of a fault: Airy stress function surface and curvatures

We considered the two-dimensional stress aspect of a fault from the viewpoint of differential geometry. For this analysis, we concentrated on the curvatures of the Airy stress function surface. We found the following: (i) Because the principal stresses are the principal curvatures of the stress function surface, the first and the second invariant quantities in the elasticity correspond to invariant quantities in differential geometry; specifically, the mean and Gaussian curvatures, respectively; (ii) Coulomb’s failure criterion shows that the coefficient of friction is the physical expression of the geometric energy of the stress function surface; (iii) The differential geometric expression of the Goursat formula shows that the fault (dislocation) type (strike-slip or dip-slip) corresponds to the stress function surface type (elliptic or hyperbolic). Finally, we discuss the need to use non-biharmonic stress tensor theory to describe the stress aspect of multi-faults or an earthquake source zone.     

Effects of environmental regulations on heavy metal pollution decline in core sediments from Manila Bay

We investigated the high-resolution heavy metal pollution history of Manila Bay using heavy metal concentrations and Pb isotope ratios together with ²¹⁰Pb dating to find out the effects of environmental regulations after the 1990s. Our results suggested that the rate of decline in heavy metal pollution increased dramatically from the end of the 1990s due to stricter environmental regulations, Administrative Order No. 42, being enforced by the Philippines government. The presented data and methodology should form the basis for future monitoring, leading to pollution control, and to the generation of preventive measures at the pollution source for the maintenance of environmental quality in the coastal metropolitan city of Manila. Although this is the first report of a reduction in pollution in Asian developing country, our results suggest that we can expect to find similar signs of pollution decline in other parts of the world as well.     

A near-infrared survey of Miras and the distance to the Galactic Centre

We report the results of a near-infrared survey for long-period variables in a field of view of 20× 30 arcmin² towards the Galactic Centre (GC). We have detected 1364 variables, of which 348 are identified with those reported in Glass et al. We present a catalogue and photometric measurements for the detected variables and discuss their nature. We also establish a method for the simultaneous estimation of distances and extinctions using the period–luminosity relations for the JHK _s bands. Our method is applicable to Miras with periods in the range 100–350 d and mean magnitudes available in two or more filter bands. While J band means are often unavailable for our objects because of the large extinction, we estimated distances and extinctions for 143 Miras whose H - and   K _s  -band mean magnitudes are obtained. We find that most are located at the same distance to within our accuracy. Assuming that the barycentre of these Miras corresponds to the GC, we estimate its distance modulus to be  14.58 ± 0.02 (stat.) ± 0.11 (syst.) mag  , corresponding to  8.24 ± 0.08 (stat.) ± 0.42 (syst.) kpc  . We have assumed the distance modulus to the Large Magellanic Cloud to be 18.45 mag, and the uncertainty in this quantity is included in the above systematic error. We also discuss the large and highly variable extinction. Its value ranges from 1.5 mag to larger than 4 mag in     except towards the thicker dark nebulae and it varies in a complicated way with the line of sight. We have identified mid-infrared counterparts in the Spitzer /IRAC catalogue of Ramírez et al. for most of our variables and find that they follow rather narrow period–luminosity relations in the 3.6–8.0 μm wavelength range.     

Thermal annealing characteristics of fission tracks in natural zircons of different ages

Fission track (FT) thermochronometry using zircon has widely been applied to the resolution of a variety of geologic problems, for which the understanding of FT annealing behaviour is essential. Thermal annealing experiments were conducted on FTs in natural zircons having different ages (ranging from ~0.6 to ~70 Ma) and radiation damage levels. We measured horizontal confined track lengths on nine zircon concentrates separated from rapidly cooled volcanic rocks, after 1 hr annealing at 400–700°C. As the annealing temperature increases, the observed tracks show a consistent and systematic length reduction in all samples, and the mean track lengths are hardly distinguishable among the nine samples for the same annealing step. Our results suggest that the thermal annealing characteristics at laboratory time‐scale are concordant among the zircons, regardless of their ages, and that identical annealing kinetics may work for Late Mesozoic to Cenozoic zircons.