Geochemical aspects of some accumulation models for primary magmas     

Sven Maaløe  A. Dana Johnston 《Contributions to Mineralogy and Petrology》1986,93(4):449-458

The compositions of primary magmas depend to some degree on the dynamic processes occurring in the partially molten region of the mantle. The compositional dependence is estimated for three models which assume either accumulation from a migmatized source region or accumulation entirely by the interstitial flow of magma. Accumulation from a migmatised region results in magmas with higher concentrations of incompatible elements than does batch melting, whereas accumulation by interstitial flow results in magmas with lower concentrations of these elements. The concentrations of refractory elements are almost independent of both the accumulation process and the degree of partial melting and are therefore usefull for the identification of primary magmas.  相似文献   

Liquid fractionation. Part IV: Scale models for liquid fractionation of calc-alkaline magmas     

Sven Maale  Alexander R. McBirney 《Journal of Volcanology and Geothermal Research》1997,76(1-2)

Liquid fractionation has been modeled experimentally using scale theory. The results confirm that under conditions of constant viscosity a low-density magma can ascend as a coherent laminar layer along the vertical walls. The results also suggest, however, that if viscosity increases with differentiation the fractionated liquid forms small centimetreized plumes not only along inclined and irregular walls and along the bottom of magma chambers, but even on vertical walls. The formation of plumes enhances the accumulation of rhyolitic magma, and may increase the efficiency of fractionation.  相似文献   

Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250°C by means of Rietveld refinement of synchrotron data     

Karen Friese  Andrzej Grzechnik  Emil Makovicky  Tonči Balić-Žunić  Sven Karup-Møller 《Physics and Chemistry of Minerals》2008,35(8):455-465

Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M₁₂(Sb,As)₄S₁₃. Measurements were performed at 25 and 250°C. For both the phases, increased Fe substitution is reflected in the increased tetrahedral ‘Cu1’–S distance (‘Cu1’ is a site of Fe substitution) and Cu2–S distances. Cu2 was refined as a split position; the Cu2–Cu2 split about the plane of the S1₂S2 triangle is about 0.56 and 0.65 Å for tetrahedrite and tennantite, respectively. Cu2–Cu2 distances in the structure cavity are 2.8–2.9 Å. Between 25 and 250°C, the lattice parameter a increased by 0.02–0.04 Å and the interatomic distances by 0.01 Å on an average. Thermal expansion coefficients of little-substituted samples are similar to those of unsubstituted samples, whereas thermal expansion appears to decrease with increasing substitution by Fe. The Cu2–Cu2 split increases at 250°C by about 0.1 Å for tetrahedrite and by more than 0.15 Å for tennantite but the cage expansion is minimal so that the Cu2–Cu2 distances in the cavity decrease with temperature. Difference Fourier maps indicate that there is little residual electron density left between the two Cu2 half-sites in tetrahedrite but this inter-site density is substantially higher in tennantite. It increases with temperature, especially in the little-substituted tennantite sample.  相似文献   

Automated Multi-class Classification of Remotely Sensed Hyperspectral Imagery Via Gaussian Processes with a Non-stationary Covariance Function     

Anna Chlingaryan  Arman Melkumyan  Richard J. Murphy  Sven Schneider 《Mathematical Geosciences》2016,48(5):537-558

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Micro-sized enterprises: vulnerability to flash floods     

Konstantinos Karagiorgos  Micha Heiser  Thomas Thaler  Johannes Hübl  Sven Fuchs 《Natural Hazards》2016,81(2):1091-1106

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Electrical properties of seafloor massive sulfides     

Giovanni Spagnoli  Mark Hannington  Katharina Bairlein  Andreas Hördt  Marion Jegen  Sven Petersen  Tea Laurila 《Geo-Marine Letters》2016,36(3):235-245

Seafloor massive sulfide (SMS) deposits are increasingly seen as important marine metal resources for the future. A growing number of industrialized nations are involved in the surveying and sampling of such deposits by drilling. Drill ships are expensive and their availability can be limited; seabed drill rigs are a cost-effective alternative and more suitable for obtaining cores for resource evaluation. In order to achieve the objectives of resource evaluations, details are required of the geological, mineralogical, and physical properties of the polymetallic deposits and their host rocks. Electrical properties of the deposits and their ore minerals are distinct from their unmineralized host rocks. Therefore, the use of electrical methods to detect SMS while drilling and recovering drill cores could decrease the costs and accelerate offshore operations by limiting the amount of drilling in unmineralized material. This paper presents new data regarding the electrical properties of SMS cores that can be used in that assessment. Frequency-dependent complex electrical resistivity in the frequency range between 0.002 and 100 Hz was examined in order to potentially discriminate between different types of fresh rocks, alteration and mineralization. Forty mini-cores of SMS and unmineralized host rocks were tested in the laboratory, originating from different tectonic settings such as the intermediate-spreading ridges of the Galapagos and Axial Seamount, and the Pacmanus back-arc basin. The results indicate that there is a clear potential to distinguish between mineralized and non-mineralized samples, with some evidence that even different types of mineralization can be discriminated. This could be achieved using resistivity magnitude alone with appropriate rig-mounted electrical sensors. Exploiting the frequency-dependent behavior of resistivity might amplify the differences and further improve the rock characterization.  相似文献   

A sound-probe for real-time checking of physical bottom characteristics     

Leif Lundgren  Sven Blomqvist 《Aquatic Sciences - Research Across Boundaries》1998,60(1):28-32

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Place and city: Operationalizing sense of place and social capital in the urban context          下载免费PDF全文

Albert Acedo  Marco Painho  Sven Casteleyn 《Transactions in GIS》2017,21(3):503-520

The academic interest in social concepts in city contexts, such as sense of place and social capital, has been growing in the last decades. We present a systematic literature review that confirms the strong relationship between sense of place and social capital, from a social sciences point‐of‐view. It also reveal that little attention has been paid to their spatial dimensions at the urban level, thereby missing the chance to exploit socio‐spatial knowledge to improve the day‐to‐day life in and functioning of the city (e.g. in planning processes, citizen participation, civic engagement). We therefore examine sense of place and social capital from a Geographic Information Science (GISc) viewpoint, and present a formal conceptualization and initial theoretical framework which explicitly describes both concepts, and the relation between them, within the context of a city and from a spatial point of view.  相似文献   

Recruitment of Demosponges (Porifera,Demospongiae) in Rocky and Coral Reef Habitats of Santa Marta,Colombian Caribbean*     

Sven Zea 《Marine Ecology》1993,14(1):1-21

Abstract. Recruitment of demosponges (Porifera, Demospongiae) was monitored bimonthly for one year (March 1987 – March 1988) on acrylic plates, and compared to cover of adults, in six rocky and coral reef habitats at Santa Marta, Colombian Caribbean, an area subjected to seasonal, upwelling-outwelling regimes. According to suggestive but not significant trends, recruitment rates are more positively influenced by the total sponge cover near groups of plates than by cover at a larger (habitat) scale; recruit mortality is lower where recruitment is higher. These findings are in agreement with a model of higher settlement (probably due to short-distance dispersal) and lower postsettlement mortality within a few meters of adult sponges. Recruitment varied seasonally, being relatively high from May to November-December during the rainy, outwelling season, when seawater temperature was warmer, water turbidity higher, and benthic algal density lower; it was very low from January to April during the dry, upwelling season.  相似文献   

The status of sea bass (Dicentrarchus labrax) stocks around England and Wales, derived using a separable catch-at-age model, and implications for fisheries management     

Pawson  Mike G.; Kupschus  Sven; Pickett  Graham D. 《ICES Journal of Marine Science》2007,64(2):346-356

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