Uptake and biological effects of synthetic glucocorticoids in common carp (Cyprinus carpio)

Uptake and biological effects of synthetic glucocorticoids (GCs) were analyzed using common carp (Cyprinus carpio). Fish were exposed to clobetasol propionate (CP) or clobetasone butyrate (CB) individually or in mixture at 1 μg L⁻¹ for 21 days. Bioconcentration factor (BCF) of CB was calculated as 100, and BCF of CP was less than 16. No effects were found in fish erythrocyte and leukocyte numbers and serum glucose levels after exposure to the selected GCs. On the other hand, serum concentrations of free amino acids significantly increased in GC-exposed groups. Thus, exposures to synthetic GCs at relatively low concentrations seemed to cause enhancement of protein degradation and subsequent increase of serum free amino acids without a corresponding increase in serum glucose levels, an effect which might be related to partial induction of gluconeogenesis by GC.     

Laboratory measurements of ‘porosity‐free’ intrinsic Vp and Vs in an olivine gabbro of the Oman ophiolite: Implication for interpretation of the seismic structure of lower oceanic crust

In order to determine ‘porosity‐free’ intrinsic ultrasonic compressional (Vp) and shear wave (Vs) velocities and Vp/Vs of an olivine gabbro from the Oman ophiolite, we developed a new experimental system using a piston‐cylinder type high‐pressure apparatus. The new system allowed us to measure velocities at pressures ranging from 0.20 to 1.00 GPa and at temperatures up to 300°C for Vp and 400°C for Vs. At room temperature, the Vp and Vp/Vs increase rapidly with pressure up to 0.40 GPa, while between 0.45 and 1.00 GPa the increase is more gradual. The change in increasing rate is attributed to closure of porosity at pressures above 0.45 GPa. Based on the linear regression of data obtained at higher pressures (0.45–1.00 GPa) and extrapolation to the lower pressures, combined with temperature derivatives of velocities of the sample measured at 1.00 GPa, we determined the intrinsic Vp and Vs of the sample as a function of pressure (P, in GPa) and temperature (T, in °C). The intrinsic velocities can be expressed as Vp (km/s) = 7.004 + 0.096 × P ? 0.00015 × T, and Vs (km/s) = 3.827 + 0.007 × P ? 0.00008 × T. We evaluated the intrinsic Vp and Vs of the olivine gabbro at oceanic crustal conditions and compared them with a velocity depth‐profile of the borehole seismic observatory WP‐2 area in the northwestern Pacific Basin. Although the intrinsic Vp (～7.0 km/s) and Vs (～3.8 km/s) for the olivine gabbro studied are comparable to those of seismic layer 3 in the WP‐2 area, the estimated vertical gradients of intrinsic velocities are significantly smaller than those reported from layer 3. These results suggest that velocity profiles of layer 3 in the WP‐2 area may reflect the presence of a minor porosity in lower oceanic crust, which closes with increasing depth and/or continuous changes in mineralogy of layer 3 rocks.     

Existence of andesitic primary magma: An example from southwest Japan

A high-magnesian andesite (SiO₂ 58.50%, MgO 9.47%) occurs at Teraga-Ike in southwest Japan. It belongs to the Setouchi volcanic rocks of middle Miocene age and carries olivine and bronzite as phenocrysts (4.2 and 1.4 modal percent, respectively). This andesite is characterized by Mg-values as high as 75, suggesting that it may be a primary andesite. Olivine phenocrysts (Fo_87–91) are in equilibrium with the groundmass (= liquid) on the basis of Fe-Mg exchange partitioning between olivine and liquid, and they have high NiO contents (up to 0.45%). Chromite inclusions in olivine and rarely bronzite have high Cr₂O₃ contents (max. 54.87%). These features strongly suggest that the Teraga-Ike andesite keeps the chemical composition of the primary magma generated in the upper mantle, and therefore verify the existence of primary andesite magmas.     

226Ra, 210Pb and 210Po disequilibria in the Western North Pacific

²²⁶Ra,²¹⁰Pb and²¹⁰Po were measured in oceanic profiles at two stations near the Bonin and Kurile trenches.²¹⁰Po is depleted by 50% on average relative to²¹⁰Pb in the surface water. In the deep water,²¹⁰Pb is about 25% deficient relative to²²⁶Ra. Based on the deficiency,²¹⁰Pb residence time with respect to removal by particulate matter was estimated to be less than 96 years in the deep water.²¹⁰Pb deficiency in the bottom water was significantly greater than that of the adjacent deep water, indicating more effective removal near or at the bottom interface.²¹⁰Pb,²¹⁰Po and Th appear to have similar overall rate constants of particulate removal throughout the water column.     

Integrated P-T Paths of the High-Pressure Rocks and Their Tectonic Implications for the Mountain-Building of the North Qilian, China

After the integration of petrographic study, geothermobarometry and Gibbs method, the synthetic P-T paths for the rocks from different geological profiles in the North Qilian, China, have been derived. The composite P-T paths from different methods indicate that all the high-pressure rocks in the Qilian area recorded P-T paths with clockwise loops starting at the blueschist facies, later reaching peak metamorphism at the blueschist facies, eclogite fades or epidote-amphibolite facies and ending up with the greenschist facies. The incremental Ar-Ar dating shows that the plateau ages for the high-pressure rocks range from 410 to 443 Ma. The plateau ages could be used as a minimum age constraint for the subduction that resulted in the formation of these high-pressure rocks in the Qilian area. It is proposed that the late-stage decompressional and cooling P-T paths with ends at the greenschist facies for these high-pressure rocks probably reflect the uplift process which could occur after shifting the arc-t     

Southward extrusion of eclogite-bearing mafic–ultramafic bodies in the Sanbagawa belt, central Shikoku, Japan

Several mafic rock masses, which have experienced eclogite facies metamorphism, are distributed in flat-lying non-eclogitic schists in an intermediate structural level (thermal core) of the Sanbagawa belt. The largest, Iratsu mass, and an associated peridotite, the Higashi-Akaishi mass, extend E–W for about 8 km, and N–S for about 3 km, and are surrounded by pelitic, basic and quartz schists. The Iratsu mass consists of metabasites of gabbroic and basaltic origin, with intercalations of ultramafic rocks, felsic gneiss, quartz schist and metacarbonate. The Iratsu mass can be divided into two layers along a WNW-trending metacarbonate layer. The Higashi-Akaishi mass consists of peridotite with intercalations of garnet clinopyroxenite. It is situated beneath the western half of the Iratsu mass, and their mutual boundary dips gently or steeply to the N or NE. These masses underwent eclogite, and subsequent epidote-amphibolite facies metamorphism as has been reported elsewhere. The Iratsu–Higashi-Akaishi masses and the surrounding rocks underwent ductile deformation under epidote-amphibolite facies (or lower P–T) metamorphic conditions. Their foliation generally trends WNW and dips moderately to the NNE, and the mineral lineation mostly plunges to the N and NE. In non-eclogitic schists surrounding the Iratsu–Higashi-Akaishi masses, the foliation generally trends WNW and dips gently or steeply to the N or S and the mineral lineation mostly plunges to the NW, N and NE. Kinematic analysis of deformation structures in outcrops and oriented samples has been performed to determine shear senses. Consistent top-to-the-north, normal fault displacements are observed in peridotite layers of the Higashi-Akaishi mass and eclogite-bearing epidote amphibolite layers of the Iratsu mass. Top-to-the-northeast or top-to-the-northwest displacements also occur in non-eclogitic pelitic–quartz schists on the northern side of the Iratsu mass. In the structural bottom of the Iratsu–Higashi-Akaishi masses and to the south, reverse fault (top-to-the-south) movements are recognized in serpentinized peridotite and non-eclogitic schists. These observations provide the following constraints on the kinematics of the rock masses: (1) northward normal displacement of Iratsu relative to Higashi-Akaishi, (2) northward normal displacement of non-eclogitic schists on the north of the Iratsu mass and (3) southward thrusting of the Iratsu–Higashi-Akaishi masses upon non-eclogitic schists in the south. The exhumation process of the Iratsu–Higashi-Akaishi masses can be explained by their southward extrusion.     

Correlations between oxygen-isotopic composition and petrologic setting in a coarse-grained Ca, Al-rich inclusion

Oxygen-isotopic compositions in conjunction with petrologic investigation have been determined for a coarse-grained type B2 Ca, Al-rich inclusion (CAI) from the reduced CV3 Vigarano using secondary ion mass spectrometry. The oxygen-isotopic compositions of minerals are distributed along the carbonaceous chondrite anhydrous mineral line indicating mixing between ¹⁶O-rich and ¹⁶O-poor nebular components. The O-isotopic heterogeneities among and within minerals in the CAI interior indicate that CAI formation started in an ¹⁶O-rich nebula and subsequently continued in an ¹⁶O-poor nebula. ¹⁶O-rich signatures of melilite and fassaite in the Wark-Lovering rim and of olivine of the accretionary rim indicate that the nebular environment during formation of the CAI returned to an ¹⁶O-rich composition after processing in an ¹⁶O-poor nebula. These O-isotopic variations in the CAI support multiple heating events in the solar nebula and indicate that the nebular environments fluctuated from ¹⁶O-rich to ¹⁶O-poor and back to ¹⁶O-rich compositions during the formation of a single CAI.     

Variations in seawater osmium isotope composition since the last glacial maximum: A case study from the Japan Sea

Concentrations of Re and Os, and the isotopic composition of Os have been measured in the Japan Sea sediments to assess the response of the Japan Sea to glacial–interglacial climate change and associated weathering fluxes. The osmium concentrations in the sediment samples analyzed vary from 59 to 371 pg/g, and ¹⁸⁷Os/¹⁸⁸Os from 0.935 to 1.042. Only ¹⁸⁷Os/¹⁸⁸Os of sediment samples from dark laminations deposited under suboxic to anoxic conditions and having elevated concentrations of Re and Os, and with ≥ 80% hydrogenous Os are explained in terms of seawater composition. Lower ¹⁸⁷Os/¹⁸⁸Os were observed for sediments deposited during the last glacial maximum (LGM) when planktonic foraminifera from the Japan Sea recorded lighter oxygen isotopic composition. Decrease in dissolved Os fluxes from continents and/or change in the composition of the dissolved load to the Japan Sea are suggested as the driving mechanisms for the observed lower LGM ¹⁸⁷Os/¹⁸⁸Os. The results of this study, coupled with lower ¹⁸⁷Os/¹⁸⁸Os during the last glacial observed at other sites from ocean basins with different lithology and contrasting sediment accumulation rates, suggest that this trend is characteristic of the global oceans.

Data from this study show that the Japan Sea recorded higher ¹⁸⁷Os/¹⁸⁸Os during the current interglacial coinciding with excursions of oxygen isotopic compositions of planktonic foraminifera to heavier values. This is explained in terms of preferential release of ¹⁸⁷Os during deglacial weathering and/or higher continental Os flux driven by warm and wet climate. This study demonstrates that Os isotopic composition of reducing margin sediments has immense potential to track variations in the seawater composition. In addition, ¹⁸⁷Os/¹⁸⁸Os of reducing sediments may be used to draw inferences about local paleoceanographic processes in semi-enclosed basins such as the Japan Sea.     

Structural characteristics off Miyagi forearc region, the Japan Trench seismogenic zone, deduced from a wide-angle reflection and refraction study

The Japan Trench subduction zone, located east of NE Japan, has regional variation in seismicity. Many large earthquakes occurred in the northern part of Japan Trench, but few in the southern part. Off Miyagi region is in the middle of the Japan Trench, where the large earthquakes (M > 7) with thrust mechanisms have occurred at an interval of about 40 years in two parts: inner trench slope and near land. A seismic experiment using 36 ocean bottom seismographs (OBS) and a 12,000 cu. in. airgun array was conducted to determine a detailed, 2D velocity structure in the forearc region off Miyagi. The depth to the Moho is 21 km, at 115 km from the trench axis, and becomes progressively deeper landward. The P-wave velocity of the mantle wedge is 7.9–8.1 km/s, which is typical velocity for uppermost mantle without large serpentinization. The dip angle of oceanic crust is increased from 5–6° near the trench axis to 23° 150 km landward from the trench axis. The P-wave velocity of the oceanic uppermost mantle is as small as 7.7 km/s. This low-velocity oceanic mantle seems to be caused by not a lateral anisotropy but some subduction process. By comparison with the seismicity off Miyagi, the subduction zone can be divided into four parts: 1) Seaward of the trench axis, the seismicity is low and normal fault-type earthquakes occur associated with the destruction of oceanic lithosphere. 2) Beneath the deformed zone landward of the trench axis, the plate boundary is characterized as a stable sliding fault plain. In case of earthquakes, this zone may be tsunamigenic. 3) Below forearc crust where P-wave velocity is almost 6 km/s and larger: this zone is the seismogenic zone below inner trench slope, which is a plate boundary between the forearc and oceanic crusts. 4) Below mantle wedge: the rupture zones of thrust large earthquakes near land (e.g. 1978 off Miyagi earthquake) are located beneath the mantle wedge. The depth of the rupture zones is 30–50 km below sea level. From the comparison, the rupture zones of large earthquakes off Miyagi are limited in two parts: plate boundary between the forearc and oceanic crusts and below mantle wedge. This limitation is a rare case for subduction zone. Although the seismogenic process beneath the mantle wedge is not fully clarified, our observation suggests the two possibilities: earthquake generation at the plate boundary overridden by the mantle wedge without serpentinization or that in the subducting slab.     

Formation of a third volcanic chain in Kamchatka: generation of unusual subduction-related magmas

The unusual development of three volcanic chains, all parallel to the trend of the subduction trench, is observed in Kamchatka at the northern edge of the Kurile arc. Elsewhere on the Earth volcanic arcs dominantly consist of only two such chains. In the Kurile arc, magmatism in the third volcanic chain, which is farthest from the trench, is also unusual in that lavas show concentrations of incompatible elements intermediate between those of the two trenchward chains. This observation can be explained by relatively shallow segregation of primary magmas and high degrees of partial melting of magmas in the third chain, compared to the conditions of magma separation expected from a simple application of the general acrossarc variation. Initial magmas in such an atypical third chain may be produced by melting of K-amphibolebearing peridotite in the down-dragged layer at the base of the mantle wedge under anomalously hightemperature conditions. Such an unusual melting event may be associated with the particular tectonic setting of the Kamchatka region, i.e. the presence of subductiontransform boundary. Such a mechanism is consistent with the across-arc variation in Rb/K ratios in the Kamchatka lavas: lowest in the third chain rocks and highest in the second chain rocks.