俄罗斯Chukchi半岛新生代碱性岩的形成和演化：熔体和流体包裹体证据

Melt and fluid inclusions were studied in the minerals of Cenozoic olivine melanephelinites from the Chukchi Peninsula, Russia.The rock contain several generations of olivine phenocrysts varying in composition at mg=0.88～0.77.The phenocrysts bear fluid and melt inclusions recording various stages of melt crystallization in volcanic conduits and shallow magma chambers.Primary fluid inclusions are CO_2-dominated with a density of up to O.93 g/cm~3.All fluid inclusions are partially leaked,which is indicated by haloes of tiny fluid bubbles around large fluid inclusions in minerals.Melt inclusions contain various daughter crystals,which were completely resorbed in thermometric experiments at about 1230℃.Assuming that this temperature corresponds to the entrapment conditions of the CO_2 fluid inclusions,the minimum pressure of the beginning of magma degassing is estimated as 800MPa.Variations in the compositions of homogenized silicate melt inclusions indicate that olivine was the earliest crystalline phase followed by clinopyroxene,nepheline and orthoclase.This sequence is in agreement with the mineralogy of the rocks.The melts are strongly enriched in incompatible trace elements and volatiles(in addition to CO_2,high C1,F,and S contents were detected).There are some differences between the compositions of melts trapped in minerals from different samples.Variations in SiO_2,FeO,and incompatible element contents are probably related to melt generations at various levels in a homogeneous mantle reservoir.     

Helium-volume dynamics of Upper Freeport coal powder and lumps

Exposure to 7 MPa of helium at room temperature alters the texture of Upper Freeport coal in a lump form. The differences in texture and porosity between coal powder and lumps may affect the transport and interaction of fluids and coal. In this work, the information about the coal texture and micro- and meso-porosity was obtained via the BET, BJH, and Dubinin–Astakhov analyses. We further investigated the free-fluid-phase volume (free-volume) effects due to helium interaction with the powder and the lumps. During the manometric experiment, helium penetration into the dry coal matrix resulted in slow relaxation of pressure. After exposure of coal to helium, there have been no significant changes of the macroscopic dimensions observed and the relaxation process can be attributed to microscopic ‘free-volume’ effects. Evolution of the sorption–desorption rates indicates that exposure to helium may change the texture and apparent (helium) density of dry coal.     

Mv Lyr: Transition from Low to High Brightness State

We present results of multicolour photometry of the nova-like binary MV Lyr in the years 2002–2003, corresponding to the transition of the star from its low (V = 17.8) to high (V = 12.3) brightness state. The transition lasted at most 200 days. During the first ∼50 days MV Lyr brightened at the rate 0.06 mag/day, and during the next ∼150 days at the rate 0.01 mag/day. The brightening was accompanied by a blue shift from 0.45 to 0.05 in V−R, interpreted as an increase of the accretion disk contribution to the total light. During the transition MV Lyr displayed well-known ‘quasi-orbital’ light variations and fast quasi-periodic oscillations with a typical time scale of tens of minutes.     

Low-frequency layer-induced dispersion in a weak-contrast vertically heterogeneous orthorhombic medium

In this paper, we consider wave propagation in a periodically layered medium with orthorhombic symmetry. The weak-contrast approximation is utilized to derive the low-frequency dispersion in effective properties for P, S1 and S2 waves. We show that the dispersion term for all effective properties is controlled by the second-order contrasts in elastic properties from the layers. We also compute the sensitivity matrices for second- and fourth-order coefficients from eigenvalues of frequency-dependent system matrix associated with kinematic parameters for individual wave modes.     

Assessment aspect of contamination of the Arctic estuary ecosystems

Estuarine ecosystem may be considered as ‘pulse-targets’ where information about contamination of all-river basin and about scale and forms of contaminants input to the seas is concentrated. The nucleus of the estuarine processes of contaminants transformation and sedimentation is the critical salinity zone. In the real natural conditions of the Arctic the salinity dependent processes are masked by hydrodynamic effect. The tasks of effective chemical and biological monitoring of Russian Arctic estuarine ecosystems are formulated.     

Pu, Cs and excess Pb in Russian Arctic sediments

The activity ratios of Pu and radiocesium isotopes have been used to delineate the major sources (such as global and close-in (debris) fallout, nuclear fuel reprocessing and fabrication plant effluents) in the environment. We have measured ²³⁸Pu, ^239,240Pu, ¹³⁷Cs, and excess ²¹⁰Pb concentrations in 107 surficial sediments as well as in 5 sediment cores collected in the summer months of 1993 and 1994 from the Ob and Yenisey Rivers (Russia) and the Kara sea. A comparison of the sediment core inventories of ^239,240Pu and ¹³⁷Cs, along with the ²³⁸Pu/^239,240Pu activity ratios, with those expected from global fallout allows us to estimate the relative amounts, if any, of reactor-derived ²³⁸Pu and ^239,240Pu from the dumped reactor sites in the study area.

In surficial sediment samples collected in 1993 and 1994, the ^239,240Pu concentrations varied between 4.2 and 856 mBq kg⁻¹, with a mean of 239 mBq kg⁻¹. In samples with a measurable ²³⁸Pu, the ²³⁸Pu/^239,240Pu activity ratios varied between 0.010 and 0.069, with an average value of 0.035 ± 0.014. This range can be compared to the average ²³⁸Pu/^239,240Pu activity ratio of 0.030 for the year 1993 from nuclear weapons testing and SNAP fallout obtained from soil studies, indicating very little (≤ 5%) additional sources of ²³⁸Pu to the sediments in the study area. The inventories of Pu in the 5 sediment cores from the study area varied between 2.67 ± 0.67 and 24.5 ± 2.2 Bq m⁻² with a mean value of 8.83 Bq m⁻². The ¹³⁷Cs concentrations in the upper 3 cm of the sediments varied between below detection limit to 71.4 Bq kg⁻¹, with a mean of 14.9 Bq kg⁻¹. The ¹³⁷Cs inventories in the 5 sediment cores varied between 156.7 ± 28.3 and 1600 ± 153.3 Bq m⁻², with a mean value of 583.3 Bq m⁻². The mean ratio of inventories of Pu to that of ¹³⁷Cs, 0.015, is comparable to the values in other places in the Arctic region. There is a significant correlation between total organic carbon and concentrations of ¹³⁷Cs, ^239,240Pu and ²¹⁰Pb, suggesting that organic matter-enriched fine particles are a likely carrier phase for these nuclides. The ratio of ¹³⁷Cs/^239,240Pu also suggests that most of these nuclides are derived from global fallout.     

Effects of the Anticyclonic Eddies on Water Masses, Chemical Parameters and Chlorophyll Distributions in the Oyashio Current Region

Data from the R/V Mirai cruise (May–June 2000) have been examined to discover how mesoscale processes associated with eddy dynamics direct affect the water masses, the distributions and the vertical fluxes of the dissolved oxygen, nutrients and dissolved inorganic carbon in the western subarctic Pacific. Using maps of the temperature, salinity, dissolved oxygen, nutrients, chlorophyll and sea-air pCO₂ difference we show that the boundaries of the anticyclone eddies in the study region were composed of high productivity coastal Oyashio water. The coastal waters were wrapped around the anticyclone eddies (thus creating a high productivity belt) and intruded inside of them. Using SeaWifs data we demonstrate that temporal variations in the position and the strength of anticyclone eddies advected the Kuril island coastal high productivity waters to the pelagic part, resulting in temporal variations of the chlorophyll in the Oyashio region. Computed vertical fluxes of the dissolved oxygen (DO), inorganic carbon (DIC) and silicate show that the anticylonic eddies in the Kuroshio-Oyashio Zone are characterized by enhanced vertical fluxes of the DO and DIC between the upper (σ_θ = 26.7–27.0) and lower (σ_θ = 27.1–27.5) intermediate layer, probably due to the intrusions of the Oyashio waters into the eddies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hierarchy of Factors of Seismic Danger in Four Towns in Colima State,México

The RADIUS methodology is applied to study the hierarchy of the factors of seismic danger in four towns of Colima state, México. These towns are situated near the western coast of Pacific ocean, within zone of highest seismic risk. The 31 indicators and five factors (Hazard, Exposure, Vulnerability, External context and Emergency response and recovery capability) of seismic danger were calculated. Their comparative analysis showed that the social factors of seismic danger might compete and even prevail over the natural factors. The recent earthquake of 21 January 2003 (Intensity up to VII–VIII MM in Colima state) was used to discuss some problems of application of RADIUS methodology in various locations, such as in Latin America.     

Focal mechanism of earthquakes in the Kamchatka-Commander region and heterogeneities of the active seismic zone

Summary Focal mechanisms of 74 shallow and 16 intermediate earthquakes (1964–1970) in the Kamchatka-Commander region are discussed. Regional stress systems and the nature of faulting are analyzed. Complex stress fields in the Kamchatka-Commander region and variable aftershock processes of strong Kamchatka earthquakes show the existence of heterogeneities of the active seismic zone in the Region.     

The characteristics of seismic signals produced by lahars and pyroclastic flows: Volcán de Colima,México

The general characteristics of seismic signals produced by pyroclastic flows (generated by either the collapse of a lava dome or an eruptive column) and lahars at Volcán de Colima, México are discussed. The paper concentrates on the 2004–2006 activity associated with and following the extrusion of andesitic block-lava in October–November 2004. It is shown that the duration of the broad-band seismic records of pyroclastic flows lasts a few minutes while the duration of seismic records of lahars continues for tens of minutes or hours. The spectra of seismic records produced by pyroclastic flows are characterized by lower peak frequencies (around 3–4 Hz) than for lahars (around 6–8 Hz). This difference in the frequency content together with the difference in the duration of seismic signals allows early diagnostic of the events in real time.