Deep Norden： Highlights of the lithospheric structure of Northern Europe, Iceland, and Greenland

We present a review of geophysical models of the continental lithosphere of Norden, which includes the Nordic countries （Denmark, Iceland, Finland, Norway, Sweden）, Greenland, and the adjacent regions of the neighbouring countries. The structure of the crust and the lithospheric mantle reflects the geologic evolution of Norden from Precambrian terrane accretion and subduction within the Baltic Shield and Greenland to Phanerozoic rifting, volcanism, magmatic crust formation, subduction and continent-continent collision at the edges of the cratons and at the plate boundaries. The proposed existence of a mantle plume below Iceland has not been uniquely demonstrated by the available seismic evidence. Its connection to the break-up of the North Atlantic Ocean c. 65 My ago is uncertain, but the 〉30 km thick crust in the strait between Iceland and Greenland may indicate the track of the plume. Using the results from seismic （reflection and refraction profiles, P- and S-wave, body-wave and surface-wave tomography）, thermal, gravity, and petrologic studies,we review the structure of the crust and the lithospheric mantle of Norden and propose an integrated model of physical properties of the lithosphere of the region, including maps of lateral variation in crustal and lithospheric thicknesses and compositional variation in the lithospheric mantle.     

Partitioning of Cu,Sn, Mo,W, U,and Th between melt and aqueous fluid in the systems haplogranite-H2O−HCl and haplogranite-H2O−HF

The partition coefficients K_D=c_fluid/c_melt of Cu, Sn, Mo, W, U, and Th between aqueous fluid and melt were measured in the systems haplogranite-H₂O–HCl and haplogranite-H₂O–HF at 2kbars, 750°C, and Ni–NiO buffer conditions using rapid-quench cold seal bombs, with many reversed runs. Concentrations of trace elements (1–1000 ppm) in the quenched aqueous fluid and in the glass were determined by plasma emission spectrometry (DCP). K_D of F is close to 1 in the system studied. K_D of Cu and Sn strongly increases with increasing Cl concentration due to the formation of chloride complexes in the aqueous fluid, while HF has no effect. However, in 2M HCl, K_D of Cu approaches 100, while K_D of Sn is below 0.1 under the same conditions. The partition coefficients of Mo and W are high if water is the only volatile present (Mo: 5.5, W: 3.5), but strongly decrease with increasing HCl and HF, due to the destabilization of hydroxy complexes. K_D of U and Th is very low in the absence of complexing agents, but strongly increases with increasing HF concentration. K_D of U also increases with increasing HCl concentration and with increasing CO₂ concentration in the system haplogranite-H₂O–CO₂, indicating the stability of chloride and carbonate complexes of U at magmatic temperatures. The data suggest a stoichiometric ratio of Cl: U=3:1 and of F:U=2:1 in these complexes. Cl-rich fluids are responsible for the formation of porphyry Cu deposits, but are much less effective in the transport of Sn. F appears not to be essential for the concentration of Mo and W in fluids evolving from a granitic magma. The different complexing behavior of U and Th in aqueous fluids may account for their fractionation during magma genesis.     

Calculations of the seasonal loadings of North Sea sediments with persistent aromatic organochlorines

The content and distribution of ΣPCB (as the sum of 24 individual components), HCB and p,p′-DDE was determined in sediments taken from the North Sea during two seasons. The mass-balance of aromatic organochlorine compounds in the upper 2 cm of sediments is calculated and dicussed in relation to pollutant dispersal.     

Frontbildung während einer Phase extremer Schichtung in der Deutschen Bucht

Zusammenfassung Es wird eine Phase sehr ausgeprägter Temperaturschichtung in der Deutschen Bucht beschrieben, die bei einer sehr stabilen Hochdruck-Wetterlage aufgetreten ist. Sie war mit deutlichen Frontbildungen und Auftriebserscheinungen verbunden. Rechnungen mit einem hydrodynamischen Modell unterstützen diese Auffassung.Eine besonders ausgeprägte Temperaturfront folgt klar der 20 m-Tiefenlinie. Daraus wird im Hinblick auf die Theorie von Pingree und Griffith [1978]) geschlossen, daß bei der herrschenden Wetterlage die Gezeitenstromturbulenz die Hauptursache für die Vermischung der Wasserschichten ist: Auftrieb spielt eine untergeordnete Rolle.

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Frontogenesis during a phase of extreme stratification in the German Bight

Summary This paper describes a phase of pronounced thermal stratification in the German Bight which developed during a period of very stable high pressure. Calculations using a hydrodynamic model support the view that it was accompanied by strong frontogenesis and upwelling.A very distinct temperature front is found along the 20 m depth contour. With regard to Pingree and Griffith's [1978] theory, we conclude from this that in such weather conditions, turbulence due to tidal currents mainly causes the water strata to mix and that upwelling is only of secondary importance.

     

Urban Community Garden Agrodiversity and Cultural Identity in Philadelphia,Pennsylvania, U.S.

Considerable research has examined the social, cultural, economic, and community benefits of urban gardening. Few studies, however, have empirically assessed factors that influence urban community garden agrodiversity or its relationship to these dimensions of gardening. We conducted an interdisciplinary study of agrodiversity and cultural identity, based certain markers of identity, including how people see themselves with respect to race, ethnicity, or place of origin, in community gardens in Philadelphia, Pennsylvania. We conducted fifty‐six semistructured interviews with gardeners with different cultural identities in eight community gardens on their motivations for urban community gardening during 2014. We conducted plant inventories of the corresponding garden plots and found 104 cultivated edible and ornamental species and 28 varieties representing 34 families. We find that although gardens with culturally diverse gardeners did not have higher species richness, the cultural identity of the gardeners influenced species selection and reason for gardening. Further, the structure, design and species composition of garden plots reflected the identities of garden members. These finding have implications for the recent institutionalization of urban agriculture into city land policies in Philadelphia and other cities in North America.