Exploration for scheelite in East Greenland — A case study     

C.P. Hallenstein  J.L. Pedersen  H. Stendal 《Journal of Geochemical Exploration》1981,15(1-3)

An intensive scheelite exploration program was carried out in Precambrian crystalline and sedimentary rocks intruded by granites of Precambrian and Caledonian ages in East Greenland (70–74°30′N). Previous heavy-mineral panning (2100 samples within an area of 100,000 km²) formed the basis for selection of scheelite-anomalous subregions (1550 km²)In the subregions, pan-concentrate samples were taken from first- and second-order rivers and from mid and side moraines of active glaciers. All samples were studied in the field under UV light, and scheelite grains were counted. A consideration of the distribution of scheelite in the samples together with the river and glacial drainage systems, led to definition of the potential source areas of the scheelite within localities of 2–5 km².Within the localities, panning of scree fines (samples every 100–200 m along talus slopes) and UV-light traverses at night led to the finding of outcropping or sub-outcropping scheelite mineralisation. Scheelite was observed associated with granite-carbonate contact zones, quartz vein stockworks, and fault zones in limestones, at nine localities within the 300-km-long zone of investigation.The heavy-mineral panning method with the counting of scheelite grains in the field and the subsequent definition of potential scheelite-bearing areas has the advantage that it is possible to execute a program from the subregional to the outcropping mineralisation stage in one field season. The investigation in this case was performed by five geologists during the 1979 2.5-month field season.  相似文献   

Rb/1bSr isochrons for the granitic plutons around Farsund,southern Norway     

Svend Pedersen  Torgeir Falkum 《Chemical Geology》1975,15(2):97-101

The granitic and charnockitic intrusions in the Precambrian migmatites around Farsund in southern Norway have previously been shown to be successively intruded as well as being geochemically different. Rb- and Sr-isotope data support the conclusion that they are intruded with a separate time interval and that the Farsund charnockite is younger (852±41 m.y.) than the Lyngdal hornblende granite (932±38 m.y.). Furthermore, the different initial ratios (0.7128 and 0.7054, respectively) disprove a comagmatic origin unless large-scale contamination has occurred.  相似文献   

Ar/Ar geochronology of the West Greenland Tertiary volcanic province     

M. Storey  R. A. Duncan  A. K. Pedersen  L. M. Larsen  H. C. Larsen 《Earth and Planetary Science Letters》1998,160(3-4):569-586

Paleocene volcanic rocks in West Greenland and Baffin Island were among the first products of the Iceland mantle plume, forming part of a larger igneous province that is now submerged beneath the northern Labrador Sea. A ⁴⁰Ar/³⁹Ar dating study shows that volcanism commenced in West Greenland between 60.9 and 61.3 Ma and that 80% of the Paleocene lava pile was erupted in 1 million years or less (weighted mean age of 60.5±0.4 Ma). Minimum estimates of magma production rates (1.3×10⁻⁴ km³ year⁻¹ km⁻¹) are similar to the present Iceland rift, except for the uppermost part of the Paleocene volcanic succession where the rate decreases to <0.7×10⁻⁴ km³ year⁻¹ km⁻¹ (rift). The timing of onset of volcanism in West Greenland coincides with the opening of the northern Labrador Sea and is also strikingly similar to the age of the oldest Tertiary volcanic rocks from offshore SE Greenland and the British–Irish province. This is interpreted as manifesting the impact and rapid (>1 m/year) lateral spreading of the Iceland plume head at the base of the Greenland lithosphere at 62 Ma. We suggest that the arrival, or at least a major increase in the flux, of the Iceland mantle plume beneath Greenland was a contributing factor in the initiation of seafloor spreading in the northern Labrador Sea. Our study has also revealed a previously unrecognised Early Eocene volcanic episode in West Greenland. This magmatism may be related to movement on the transform Ungava Fault System which transferred drifting from the Labrador Sea to Baffin Bay. A regional change in plate kinematics at 55 Ma, associated with the opening of the North Atlantic, would have caused net extension along parts of this fault. This would have resulted in decompression and partial melting of the underlying asthenosphere. The source of the melts for the Eocene magmatism may have been remnants of still anomalously hot Iceland plume mantle which were left stranded beneath the West Greenland lithosphere in the Early Paleocene.  相似文献   

Elastic Kirchhoff-Helmholtz Synthetic Seismograms     

A. Druzhinin  H. Pedersen  M. Campillo  W. Kim 《Pure and Applied Geophysics》1998,151(1):17-45

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Non-Stoichiometric magnesian spinels in shale xenoliths from a native iron-bearing andesite at Asuk,Disko, central West Greenland     

Asger Ken Pedersen 《Contributions to Mineralogy and Petrology》1978,67(3):331-340

A strongly reduced native iron-bearing andesite breccia from Disko contains graphite-rich modified shale xenoliths with magnesian spinels. These spinels are free from or very poor in ferric iron and vary considerably within the MgO-FeO-Cr₂O₃-Al₂O₃ compositional space. Through a simple substitution of the type 3 (Mg, Fe)²⁺ ⇆ 2(Al, Cr)³⁺+□_vacancy, the spinels vary from stoichiometric (Mg, Fe)²⁺ (Al, Cr)³⁺ ₂O₄ towards (Al, Cr)₂O₃. The simple substitution of Cr for Al suggests that Cr was accepted into the spinel structure as Cr³⁺, despite the reduced nature of the enclosing andesite. The most magnesian spinels are cation deficient spinel_ss in the synthetic systems MgO-Al₂O₃ and MgO-Al₂O₃-Cr₂O₃. The absence of exolved (Al, Cr)₂O₃-component is probable due to rapid quenching.  相似文献   

Industrial minerals and rocks, aggregates and natural stones in the Nordic countries     

Kurt Johansson Rune B. Larsen Markku J. Lehtinen Lars Persson Mika Raeisaenen Stig A. Schack Pedersen Paer Weihed Nils-Gunnar Wik 《《幕》》2008,31(1):133-139

The Nordic countries, including Greenland, have a long tradition in mining. The industrial minerals sector is expanding in most Nordic countries and extensive development has taken place during the last few years. The main commodities mined are carbonate rocks, quartz, feldspar, apatite, olivine and talc.
A number of diferent types of dimension stones are quarried in all countries. Rock aggregates are increasingly important, replacing sand and gravel aggregate as construction materials in some countries due to the need to protect ground water supplies.  相似文献   

Stability of an immersed tunnel in offshore conditions under deep water wave impact     

T. Kasper  J.S. Steenfelt  L.M. Pedersen  P.G. Jackson  R.W.M.G. Heijmans 《Coastal Engineering》2008

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Mapping fisheries in the German exclusive economic zone with special reference to offshore Natura 2000 sites     

Søren Anker Pedersen  Heino O. Fock  Anne F. Sell 《Marine Policy》2009

Large intensity and diversity of human activities result in an increase in complexity in the utilization of space. This paper describes the fisheries and a method to map fishing efforts and catches of different fleets by combining vessel monitoring system (VMS) data and logbook data. The method makes it possible to explore the spatial and temporal variability of fishing and the potential impacts of proposed management measures on the fisheries. The method is proposed to be used in the development of management plans for marine protected areas such as Natura 2000 sites, designated to protect vulnerable habitats and species.  相似文献   

Introduction to the Proceedings of the ECONORTH Symposium on Ecosystem Dynamics in the Norwegian and Barents Sea     

Torstein Pedersen  Kurt S. Tande  John G. Pope   《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1893

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Sulfide intrusion in the tropical seagrasses Thalassia testudinum and Syringodium filiforme     

Marianne Holmer  Ole Pedersen  Dorte Krause-Jensen  Birgit Olesen  Malene Hedegrd Petersen  Stephanie Schopmeyer  Marguerite Koch  Bente Aa. Lomstein  Henning S. Jensen 《Estuarine, Coastal and Shelf Science》2009,85(2):319-326

Sulfur and oxygen dynamics in the seagrasses Thalassia testudinum and Syringodium filiforme and their sediments were studied in the US Virgin Islands (USVI) in order to explore sulfide intrusion into tropical seagrasses. Four study sites were selected based on the iron concentration in sediments and on proximity to anthropogenic nutrient sources. Meadow characteristics (shoot density, above- and below-ground biomass, nutrient content) were sampled along with sediment biogeochemistry. Sulfide intrusion was high in T. testudinum, as up to 96% of total sulfur in the plant was derived from sediment-derived sulfides. The sulfide intrusion was negatively correlated to the turnover of sulfides in the sediments regulated by both plant parameters and sediment sulfur pools. Sediment iron content played an indirect role by affecting sulfide turnover rates. Leaf production was negatively correlated with sulfide intrusion suggesting that active growth reduced sulfide intrusion. Sulfide intrusion was lower in S. filiforme (up to 44%) compared to T. testudinum consistent with a higher internal nighttime oxygen concentrations found for S. filiforme. When S. filiforme can take advantage of its ability to maintain high internal oxygen concentrations, as was the case on the USVI, it could increase its success in colonizing unvegetated disturbed sediments with potentially high sulfide concentrations.  相似文献