PCBs and organochlorine pesticides in shag (Phalacrocorax aristotelis) eggs from the central Irish Sea: a preliminary study     

Janette R. Allen  Anu Thompson 《Marine pollution bulletin》1996,32(12):890-892

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The importance of different types of magmatism in VHMS mineralisation: evidence from the geochemistry of the host volcanic rocks to the Benambra massive sulphide deposits, Victoria, Australia     

A. J. Stolz  G. R. Davies  R. L. Allen 《Mineralogy and Petrology》1997,59(3-4):251-286

Summary The Wilga and Currawong Cu-Zn massive sulphide deposits in southeastern Australia are hosted by a deformed sequence of Upper Silurian basaltic to rhyolitic volcanic and sedimentary rocks. The syn-volcanic mineralisation occurs immediately above a thick package of rhyolitic volcanic rocks and volcaniclastic rocks (Thorkidaan Volcanics), and is overlain by relatively thin intercalated sills, intrusive domes and flows of basalt, andesite and dacite (Gibson's Folly Formation). The Thorkidaan Volcanics haveNd(420Ma) = -2.2 to - 9.8 and are considered to have been derived by partial melting of older crustal rocks, whereas the basalt-andesite-dacite hangingwall sequence has(Nd(415Ma) = -0.5 to + 2.0 suggesting derivation from a relatively undepleted mantle source. Relatively high-Ti andesitic to dacitic rocks from the Bumble Creek area haveNd(415Ma) = +5.2 to +5.9 suggesting affinities with Ordovician volcanic rocks elsewhere in the Lachlan Fold Belt. The Thorkidaan Volcanics display a limited silica range (73 to 79 wt.%), but have distinctive minor and trace element variations indicating a substantial fractionation history involving feldspar and several accessory phases. Major and trace element compositions of the basalt-andesite-dacite suite display regular variations consistent with a cogenetic relationship by fractional crystallisation. The basaltic rocks mostly have low TiO₂ (< 0.8 wt.%) and other chemical characteristics such as high Zr/Nb and La/Nb which suggest formation in a subduction-related setting; probably an embryonic back-arc basin developed on stretched continental lithosphere, or in small pull-apart basins developed adjacent to a transtensional margin. The magmatic history and paleogeography reflect an extensional tectonic and magmatic cycle comprising uplift, rhyolitic magmatism from crustal melting, extension, subsidence, and penetration of a mantle-derived basalt-andesite-dacite suite up extensional faults to the sea floor. Massive sulphide ores are located exactly at the stratigraphic change from rhyolitic to more mafic mantle-derived magma types. Consideration of the types of mineralisation associated with crustal, S-type granitoids, coupled with thermal constraints limiting the capacity of small bodies of silicic magma to initiate and sustain hydrothermal convection cells of reasonable size, suggests that in the absence of coeval mafic magmatism, S-type crustal-derived silicic volcanic packages are likely to be barren of VHMS deposits. Mineralisation occurs in association with mantle-derived basalt-andesite-dacite suites that either provide the necessary heat to facilitate leaching of the footwall volcanic rocks, or contribute metal-rich hydrothermal solutions during fractional crystallisation, or both.

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Die Bedeutung verschiedener Typen von Magmatismus für VHMS Mineralisationen: Die Geochemie der vulkanischen Nebengesteine der massiven Sulfid-Lagerstätte von Benambra, Victoria, Australien

Zusammenfassung Die massiven Cu-Zn-Sulfid-Lagerstätten von Wilga und Currawong in Südostaustralien treten in einer tektonisch beanspruchten Abfolge von obersilurischen, basaltischen bis rhyolitischen Vulkaniten und Sedimenten auf. Die syn-vulkanische Vererzung ist unmittelbar oberhalb einer mächtigen Abfolge von rhyolitischen Vulkaniten und Vulkanoklastiten (Thorkidaan Vulkanite) zu finden, darüber folgen relativ dünne wechsellagernde Ge, Intrusiv-Dome und Ergüsse von Basalt, Andesit und Dacit (Gibson's Folly Formation). Die Thorkidaan Vulkanite habenNd(420Ma) =-2,2 bis - 9,8 und dürften durch partielle Aufschmelzung älterer krustaler Gesteine entstanden sein. Die Basalt-Andesit-Dacit-Abfolge im Hangenden hat jedochNd(415Ma) = -0,5 bis + 2,0, was auf Herkunft aus einer relativ wenig verarmten Mantelquelle hinweist. Relativ Ti-reiche andesitische bis dacitische Gesteine aus dem Gebiet vom Bumble Creek zeigenNd(415) = +5,2 bis + 5,9. Dies weist auf Beziehungen mit Ordovicischen Vulkaniten in anderen Teilen des Lachlan-Gürtels hin. Die Thorkidaan Vulkanite zeigen SiO₂-Gehalte von 73 bis 79 Gew. %, und charakteristische Variationen der Haupt- und Spurenelementgehalte. Diese lassen eine signifikante Fraktionierung erkennen, an der Feldspäte und verschiedene andere Nebengemengteile beteiligt waren. Die Haupt- und Spurenelementzusammensetzungen der Basalt-Andesit-Decit-Abfolge zeigt normale Variationen, die auf co-genetische Beziehungen mit fraktionierter Kristallisation hinweisen. Die basaltischen Gesteine haben niedrige Gehalte an TiO₂ (< 0, 8 gew. %) sowie hohe Zr/Nb und La/Nb Verhältnisse, die auf Bildung in einem Subduktionsbereich, wahrscheinlich in einem embryonischen Back-Arc Becken, das sich auf ausgedünnter kontinentaler Lithosphäre oder in einem kleinen Pull-Apart Becken in der Nähe eines transtensionalen Randes entwickelt hat, hinweisen. Die magmatische Entwicklungsgeschichte und die Palägeographie weisen auf Dehnungs-Tektonik und auf einen magmatischen Zyklus hin, der Hebung,rhyolitischen Vulkanismus infolge von Krustenaufschmelzung, Extension, Absenkung und Durchdringung mit einer vom Mantel bezogenen Basalt-Andesit-Dacit-Suite entlang von Verwerfungen auf den Meeresboden erkennen läßt. Massive Sulfiderze kommen genau an der stratigraphischen Grenze von rhyolitschen zu mafischen Magmatypen mit Mantel-Ursprung vor. Hier ist es erforderlich, die Vererzungstypen, die zusammen mit krustalen S-Typ Granitoiden vorkommen, ebenso zu erwägen, wie die thermalen Aspekte, die die Fähigkeit kleiner saurer Magmenkörper limitieren, hydrothermale Konvektionszellen ausreichender Größe in Gang zu setzen und zu erhalten. Das weist darauf hin, daß bei Fehlen von gleichaltrigem mafischem Magmatismus saure vulkanische Abfolgen mit Krustenherkunft sehr wahrscheinlich keine VHMS-Lagerstätten führen können. Diese Vererzungen sind an Basalt-Andesit-Dacit-Abfolgen mit Mantelherkunft gebunden, die entweder die notwendige Wärmequelle für die Auslaugung vulkanischer Gesteine im Liegenden lieferten und/oder metallreiche hydrothermale Lösungen während fraktionierter Kristallisation verfügbar machten.

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The application of fecundity estimates to determine the spawning stock biomass of Irish Sea Nephrops norvegicus (L.) using the annual larval production method     

Briggs  R. P.; Armstrong  M. J.; Dickey-Collas  M.; Allen  M.; McQuaid  N.; Whitmore  J. 《ICES Journal of Marine Science》2002,59(1):109-119

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Water Quality Improvements in Liverpool Docks: The Role of Filter Feeders in Algal and Nutrient Dynamics     

Stephen B.  Wilkinson  Weizhong  Zheng  Janette R.  Allen  Nicola J.  Fielding  Vanessa C.  Wanstall  George  Russell Stephen J.  Hawkins 《Marine Ecology》1996,17(1-3):197-211

Abstract. The redevelopment of disused docks around Liverpool into areas suitable for shops, offices, housing and recreational watersports has necessitated the maintenance of good water quality in these areas. The main source of water to the docks is the River Mersey, which contains high concentrations of nutrients, encouraging algal blooms - including potentially nuisance species - in the enclosed dock basins. Since 1988 an extensive monitoring programme has been run sampling the hydrography, plankton and benthos of the docks. During this period there has been an improvement in water quality, including a reduction in summer phytoplankton biomass and anoxic bottom water. There are strong indications that phytoplankton biomass has been severely reduced by the filter feeding of Mytifus edulis . Changes in the composition of the benthic community since 1988 suggest that the large population of M. edulis is now suffering from limited recruitment. The long-term development and stability of the system is discussed with reference to community succession and its link to ecosystem functioning.  相似文献   

A carbon and nitrogen flux model of mussel digestive gland epithelial cells and their simulated response to pollutants     

McVeigh A  Allen JI  Moore MN  Dyke P  Noble D 《Marine environmental research》2004,58(2-5):821-827

The mussel digestive gland epithelial cells provide a key interface between the organism and pollutants such as aromatic hydrocarbons. The simulation of their uptake and export mechanisms as well as an internal protein degradation pathway, and any subsequent disruption to any of them, has been undertaken. A computational model is described, which simulates the flow of carbon and nitrogen through a mussel's digestive cell. The model uses a compartmentalised view of the cell with inviolate 'pipelines' connecting each of the volume-variable partitions. Only the major physiological pathways relevant to the flow of either carbon or nitrogen or volume are modelled. Simulated response to hydrocarbon exposure is examined.  相似文献   

Growth, survival, diet, and on-growing husbandry of haddock Melanogrammus aeglefinus in tanks and netpens     

Treasurer  James W.; Sveier  Harald; Harvey  Warren; Allen  Roddy; Cutts  Christopher J.; Mazorra de Quero  Carlos; Ford  Leslie 《ICES Journal of Marine Science》2006,63(2):376-384

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A numerical method for the solution of a line source under a free surface     

Iskender Sahin  Assistant Professor  Allen H. Magnuson  Asssciate Professor 《Ocean Engineering》1984,11(5):451-461

A modified source-and-dipole type singularity panel method is proposed to calculate the flow properties for an oscillating arbitrary body in the presence of a free surface. The technique is based on Green's identity whereby the boundary value problem is expressed as a boundary integral equation which is solved numerically. The free-space Green function is used in the integral equation. To demonstrate the feasibility of the method, the problem of a pulsating submerged line source under a free surface is treated and results are compared with the exact solution.An excellent agreement with the theory is obtained for panel density of about ten panels per wavelength and paneled water surface length of two wavelengths with very low computing times, indicating the feasibility of the method for unsteady water wave problems.  相似文献   

Fossil spreading center and faults within the Panama Fracture Zone     

Allen Lowrie  Thomas Aitken  Paul Grim  Linda McRaney 《Marine Geophysical Researches》1979,4(2):153-166

The north/south-trending Panama Fracture Zone forms the present eastern boundary of the Cocos Plate, with the interplate motion being right-lateral strike-slip. This fracture zone is composed of at least four linear troughs some hundreds of kilometers in length. Separate active or historic faults undoubtedly coincide with each trough. The greatest sediment fill is found in the easternmost trough. Surface and basement depths of the western trough are generally greater than those of the other three; the western trough contains the least sediment, and is most continually linear. Morphology and sediments suggest that the principal locus of strike-slip movement within the fracture zone probably migrated incrementally westward from one fault-trough to another. From north to south, the fracture zone apparently narrows from the continental intersection to approximately 5°30N, and again widens from about 5°N to at least 3°N. Residual E/W-trending magnetic anomalies are centered between two of the four troughs; sea floor spreading in a north-south direction is interpreted to have occurred between 5°30N and 7°N from 4.5 m.y. ago to 2 m.y. ago, with the symmetric center roughly coinciding with a rift valley at 6°10N, 82°30W.  相似文献   

Distribution of lifetimes for coronal soft X-ray bright points     

Leon Golub  Allen S. Krieger  Giuseppe S. Vaiana 《Solar physics》1976,47(1):79-90

We have measured the lifetimes of all compact emission features visible on three sets of high time resolution soft X-ray images. The spectrum of lifetimes is found to be heavily weighted toward short lifetimes. The number of features present on the disk which live 2–48 hours is at least ten times as great as the number living more than 48 hours. The distribution of lifetimes can be fit in all three cases by a four-parameter function N(t) = N _s exp(-t/ _s ) + N _L exp(-t/ _L ), with _s = 8.7±0.2, _L = 35±4 and N _s 10N _L . Features living two days or less have a very broad latitude distribution (Golub et al., 1974, 1975) whereas nearly all longer-lived features are found within 30° of the equator. The growth rates of long-lived vs short-lived points are the same to within 20%, the major difference being that long-lived points continue to grow and generally reach larger sizes.Harvard College Observatory/Smithsonian Astrophysical Observatory.  相似文献   

Investigation of Uranus,its satellites,and distant interplanetary phenomena by spacecraft techniques     

J.A. Van Allen 《Icarus》1975,24(3):277-279

A brief digest is given of the principal scientific objectives that can be addressed effectively, and perhaps uniquely, by spacecraft missions to Uranus. Practical considerations favor the launching of such missions in late 1979, with subsequent swing-bys of Jupiter and arrival at Uranus in late 1986.  相似文献