Schwefel-Isotopenuntersuchungen an der Blei-Zink-Erzlagerstätte Grund (Westharz,Bundesrepublik Deutschland)     

H. Sperling  H. Nielsen 《Mineralium Deposita》1973,8(1):64-72

Zusammenfassung Die S-Isotopenverteilung wurde an 67 Sulfid- und 17 Barytproben aus der Blei-Zink-Erzlagerstätte Grund untersucht. Die ³⁴S-Werte der Zinkblende der Mineralisationsphase II liegen im Westfeld-Erzmittel I und in den östlich anschließenden Erzmitteln zwischen +4 und +6, in dem am weitesten westlich liegenden Westfeld-Erzmittel II zwischen +6 und +10. Die Werte für Bleiglanz der Mineralisationsphase II sind +2 bis +4 bzw. +4 bis +7. Die Sulfide der Mineralisationsphase III haben allgemein niedrigere -Werte. Koexistierende Sulfide zeigen eine deutliche Fraktionierung, wobei stets _ZnS > _PbS ist; die Differenz beträgt in der Mineralisationsphase II im Mittel 1,8, in der Phase III 3. Dies deutet auf niedrigere Bildungstemperatur der Minerale der Phase III hin. Zur genetischen Deutung der beobachteten -Abnahme beim Übergang zur Mineralisationsphase II werden vier Modelle diskutiert. Baryte zeigen innerhalb der Lagerstätte recht einheitliche ³⁴S-Werte zwischen +11 und +14,5%. Diese Einheitlichkeit wird durch den Einfluß deszendenter Zechstein-Lösungen erklärt.

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³⁴S-values are given for 67 sulfide and 16 barite specimens from the Pb-Zn-deposit Grund (Harz mountains, W-Germany). In the central part of the deposit the sulfide 's of the first major mineralization (phase II) range from: ZnS +4 to +6 and PbS +2 to +4. The sulfides of the second major mineralization (phase III) are depleted in ³⁴S and range from: ZnS +2 to +4, PbS –1,4 to 3. The sulfides at the western end of the vein system are heavier; the phase II minerals ranging from: ZnS +6 to 10 and PbS +4 to 7. The mean -difference between co-existing ZnS and PbS in phase II is 1,8, in phase III 3. This indicates lowering of temperature of formation for the phase III ore. Four models have been set up in order to explain the observed -variation. Barites with rather uniform 's from +11 to +14,5 are probably affected by descendent solutions from overlying sulfate sediments of Permian age.

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Schwefel-Isotope aus Blei-Zink-Erzen von Oberschlesien     

Kurt v. Gehlen  Heimo Nielsen 《Mineralium Deposita》1969,4(3):308-310

Zusammenfassung Extrem schwerer Schwefel (bis zu ³⁴S=+67) in den Sulfiden aus den Pb-Zn-Erzen in Carbonatgesteinen Oberschlesiens (Górny lsk) wird als Beweis für eine Beteiligung sulfat-reduzierender Bakterien (und wahrscheinlich hochsalinarer Lösungen) bei der Erzbildung angesehen.

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Extremely heavy sulfur (up to ³⁴S=+67) in sulfides from the lead-zinc ores in carbonate rocks of Upper Silesia (Górny lsk) seems to prove a participation of sulfate-reducing bacteria (and probably of highly saline solutions) in the formation of the ores.

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The geochemistry and petrogenesis of the lavas of the Vulsinian District,Roman province,Central Italy   总被引：1，自引：0，他引：1  

Paul M. Holm  Sten Lou  Åge Nielsen 《Contributions to Mineralogy and Petrology》1982,80(4):367-378

The Vulsinian lavas are dominated by a suite of undersaturated leucite-bearing basic to intermediate compositions. The remaining lavas are mainly oversaturated and have shoshonitic affinities. One hundred and thirty-five samples have been analysed for major elements and most for 20 trace elements. Twenty-seven lavas have been analysed for REE. They are all perpotassic (for the undersaturated lavas: K₂O/Na₂O=2–8) and have very high LIL element concentrations, (e.g. Rb=400–800 ppm, Th=25–150 ppm, REE/REE_cho=c.200, (LREE/HREE)_cho=c.20) even in the most basic rocks.The undersaturated lavas appear to be interrelated by fractional crystallization of cpx±olivine (from 14 to 11 wt.% CaO), cpx+leu±plg±mica (from 11 to 8 wt.% CaO), cpx+leu+plg+apa+magnetite±mica (from 8 to 5 wt.% CaO), and additional sanidine (or hyalophane)±haüyne (from 5 to 3 wt.% CaO). The saturated lavas and the few slightly undersaturated shoshonite basalts are thought to be evolved from the undersaturated magma(s) by crustal contamination or mixing with silica-rich magmas. The parental Vulsinian magma having: Mg-value=c.73, Cr=300–700 ppm, Ni=100–125 ppm, Sc= 40–50 ppm, Fo_89–92, Di_77–97 approximates a primary, mantle-derived liquid. Enrichment in LIL elements (incl. REE) and LREE/HREE suggest a small degree of partial melting from fertile mantle; whereas the low concentrations of Na, Ti and P suggest larger degrees of partial melting. This indicates that either the primary magma or the parental mantle was metasomatized by a fluid, which previously equilibrated with subducted continental material. This model agrees with published high ¹⁸O, high ⁸⁷Sr/⁸⁶Sr and low ¹⁴³Nd/¹⁴⁴Nd.  相似文献   

The ultramafic cumulate series,Gardiner complex,East Greenland     

T. F. D. Nielsen 《Contributions to Mineralogy and Petrology》1981,76(1):60-72

The ultramafic cumulate series of the ultramafic, alkaline and carbonatite bearing Gardiner complex in East Greenland is divided in: 1) Contact zone of plagio-clase-bearing alkaline rocks chilled to the surrounding gneisses and alkaline lavas; 2) a banded sequence of dunites to mt-pyroxenites; 3) a zoned dunite — cpx-dunite ring and 4) in the centre of the complex ol-pyroxenites and mt-pyroxenites.The zones and bands are superimposed with gradational contacts and are increasingly younger towards the centre of the complex. Primocrysts and intercumulus phases, which are equivalent to phenocryst phases in magmatic liquids show that these rocks accumulated from nephelinitic to nepheline-hawaiitic magmas and the contact rocks from less alkaline basanitic magma types similar to the regional alkaline magmas.The cumulates apparently formed in a magma chamber of a nephelinitic volcano, resting on the regional basalts of the Kangerdlugssuaq area.  相似文献   

Identification of damage in reinforced concrete structures from earthquake records- optimal location of sensors     

P.S. Skjærbæk  S.R.K. Nielsen  A.?. Çakmak 《Soil Dynamics and Earthquake Engineering》1996,15(6):347-358

A method for the localization of structural damage in seismically excited reinforced concrete (RC) structures using a measured acceleration response time series is presented. From the measured response of some or all storeys, the two lowest smoothed eigenfrequencies and mode shape coordinates are estimated. These estimated values are used as an input to a developed substructure iteration method where local storey damages are estimated in such a way that these smoothed values are reproduced. The local damage indicator of a substructure is defined as the average reduction of the stiffness matrix of the initial undamaged substructure. The method is applied to simulated data of a six-storey, two-bay test frame (scale 1:5) that is to be tested at the Structural Laboratory of Aalborg University, Denmark. The simulations are performed using the non-linear finite element program SARCOF. Special emphasis is put on the investigation of the optimal location of measurement sensors, i.e. at which locations along the structure is the most information about the damage distribution gained. In all cases it is assumed that measurements are performed at top storey and ground surface, and the investigations are concentrated on putting one or two more measurement points in between. The two cases where the structure is excited in the first and second mode are investigated, and it is found that in general the sensors should be placed in the lower part of the structure. Furthermore, it is found that the method provides good results even when only the measurements at top storey and ground surface are used.  相似文献   

A faster simulation method for the stochastic response of hysteretic structures subject to earthquakes     

H.U. Köylüo?lu  S.R.K. Nielsen  A.?. Çakmak 《Soil Dynamics and Earthquake Engineering》1996,15(6):359-368

A semi-analytical forward-difference Monte Carlo simulation procedure is proposed for the determination of the lower order statistical moments and the joint probability density function of the stochastic response of hysteretic non-linear multi-degree-of-freedom structural systems subject to nonstationary gaussian white noise excitation, as an alternative to conventional direct simulation methods. The method generalizes the so-called Ermak-Allen algorithm developed for simulation applications in molecular dynamics to structural hysteretic systems. The proposed simulation procedure rely on an assumption of local gaussianity during each time step. This assumption is tantamount to various linearizations of the equations of motion. The procedure then applies an analytical convolution of the excitation process, hereby reducing the generation of stochastic processes and numerical integration to the generation of random vectors only. Such a treatment offers higher rates of convergence, faster speed and higher accuracy. The procedure has been compared to the direct Monte Carlo simulation procedure, which uses a fourth-order Runge-Kutta scheme with the white noise process approximated by a broad band Ruiz-Penzien broken line process. The considered system was a multi-dimenensional hysteretic shear frame, where the constitutive equation of the hysteretic shear forces are described by a bilinear hysteretic model. The comparisons show that significant savings in computer time and accuracy can be achieved.  相似文献   

Panel methods for computing wave loads on a vertical cylinder     

A. Berg  F.G. Nielsen 《Applied Ocean Research》1991,13(6):320-326

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Supply regimes in fisheries     

Max Nielsen 《Marine Policy》2006

Supply in fisheries is traditionally known for its backward bending nature, owing to externalities in production. Such a supply regime, however, exist only for pure open access fisheries. Since most fisheries worldwide are neither pure open access, nor optimally managed, rather between the extremes, the traditional understanding of supply regimes in fisheries needs modification. This paper identifies through a case study of the East Baltic cod fishery supply regimes in fisheries, taking alternative fisheries management schemes and mesh size limitations into account. An age-structured Beverton–Holt based bio-economic supply model with mesh sizes is developed. It is found that in the presence of realistic management schemes, the supply curves are close to vertical in the relevant range. Also, the supply curve under open access with mesh size limitations is almost vertical in the relevant range, owing to constant recruitment. The implications are that the effects on supply following from e.g. trade liberalisation and reductions of subsidies are small in several and probably most fisheries worldwide.  相似文献   

Chondrichthyans as an umbrella species-complex for conserving South African biodiversity     

GJ Osgood  ME McCord  JK Baum 《African Journal of Marine Science》2020,42(1):81-93

Conservation surrogates, such as umbrella and flagship species, could help focus South Africa’s limited resources for research and management and enhance the conservation gains from marine protected areas (MPAs). Sharks, rays and chimaeras (Chondrichthyes), which are charismatic and ecologically diverse, are potential umbrella candidates, but tests of the ecological suitability of putative marine umbrella species are lacking. Using baited remote underwater video in and around two MPAs in the Western Cape Province, we assessed the potential of chondrichthyans as an umbrella species-complex by quantifying the relationships and co-occurrence patterns between chondrichthyan abundance and diversity and those of other taxa (primarily teleosts and crustaceans). Sites with abundant chondrichthyans, with catsharks or large sharks (>1 m total length), all had significantly greater abundance and diversity of these other taxa, and associations with species of commercial and conservation interest (e.g. roman Chrysoblephus laticeps). Endemic scyliorhinids (notably dark catshark Haploblepharus pictus) and the broadnose sevengill shark Notorynchus cepedianus also had many strong positive co-occurrences (28% and 21% of interactions, respectively). The puffadder catshark H. edwardsii had the highest centrality of any species, denoting its high connectedness to other taxa. Overall, chondrichthyans, especially the dark and puffadder catsharks and the broadnose sevengill shark, show strong potential as an umbrella species-complex in South Africa.  相似文献   

Managing marine genetic diversity: time for action?   总被引：1，自引：0，他引：1  

Kenchington  Ellen; Heino  Mikko; Nielsen  Einar Eg 《ICES Journal of Marine Science》2003,60(6):1172-1176

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