Particle Size Distributions of Clay-rich Sediments and Pure Clay Minerals: A Comparison of Grain Size Analysis with Sedimentation Field-Flow Fractionation     

Martin Hassellöv  Benny Lyvén  Henrik Bengtsson  Ragna Jansen  David R Turner  Ronald Beckett 《Aquatic Geochemistry》2001,7(2):155-171

Two clay-rich coastal sediment samples have been characterised together with three pure clays identified as major components of the sediment samples. The mineralogy of the sediments was determined by X-ray diffraction, and their bulk properties measured (organic carbon content, leachable iron and manganese, surface area and cation exchange capacity). A simple approach is used to model the properties of the sediments from those of their pure clay components. Good agreement is found for cation exchange capacity and specific surface area indicating that the clay minerals are the most important constituents influencing the sediments' surface properties. Particle size distributions were assessed by conventional grain size analysis, and also by Sedimentation Field-Flow Fractionation (SedFFF). These two approaches yield sharply differing size distributions; in particular, conventional grainsize analysis indicates a much greater proportion of submicron particles. Similar results are obtained from analysis of pure clays. The most likely reason for this is artifacts introduced in the unavoidable 1 m prefractionation used for SedFFF.  相似文献   

Kinetics of intracrystalline order-disorder reactions in tremolite     

Henrik Skogby 《Physics and Chemistry of Minerals》1987,14(6):521-526

The temperature dependent Fe-Mg distribution in tremolite from Zillertal, Austria was investigated using Mössbauer spectroscopy. The standard free energy change for the exchange reaction Fe²⁺(M4)+Mg(M2)=Mg(M4)+Fe²⁺(M2) decreases with increasing temperature, corresponding to an enthalpy term of 9.2±1.5 kcal/mole and an entropy term of 1.9±1.7 cal/mole K. Kinetic experiments performed as hydrothermal runs, yield an activation energy of 70±7 kcal/mole for the disordering reaction. Difficulties in analysing the very small amount of Mg(M4) in the natural sample introduce large errors in the calculation of cooling rates for the natural rock. The estimated error in the Mg(M4) site occupancy results in a shift of the obtained cooling rate of about three orders of magnitude, making tremolite less useful for estimations of rock cooling rates.  相似文献   

Geochemical prospecting for stratabound mineralization in late Precambrian sediments of East Greenland (72–74°N)     

Henrik Stendal  Martin Hock   《Journal of Geochemical Exploration》1981,15(1-3)

A geochemical investigation was carried out mainly in a 14-km thick sedimentary sequence of late Precambrian age. The project included analysis of rock samples and drainage samples for Cu, Co, and Zn. The drainage samples were heavy-mineral concentrates and stream sediment samples.The results for the drainage sediments distinguish three well defined cupriferous horizons in the sedimentary column. Lithogeochemical studies of quartzites, pelites, and carbonates confirm that the anomalous values obtained in the drainage sediments arise from several Cu-mineralized horizons.The study has shown that geochemical prospecting appears to be well suited to Cu prospecting in Central East Greenland under arctic climate conditions even with a low sampling density of one sample per 5–10 km² for the drainage samples, and one sample per 10–100 m of the sedimentary stratigraphic column for the rock samples.  相似文献   

Spatial restructuring and land consolidation of urban-rural settlement in mountainous areas based on ecological niche perspective   总被引：4，自引：3，他引：1  

Zhaowu Yu  Lishan Xiao  Xiji Chen  Zhichao He  Qinghai Guo  Henrik Vejre 《地理学报(英文版)》2018,28(2):131-151

With the socio-economic development associated with urbanization, the urban-rural relationship has changed across the world. In China, due to the urban-rural dual structure, these changes turn out to be more complicated. Spatial restructuring are suggested as the main strategies and spatial supporting platforms for urban-rural development. However, the theory still lacks solid methodology and support from systematic empirical studies. This study seeks an adequate scientific methodology and discusses the difference of urban-rural transformation in plains and mountainous areas. A case in Shanghang County, China, demonstrates: 1) The compound ecological niche model can be a suitable approach in urban-rural restructuring, especially in mountainous areas. 2) The urban-rural development area with highly inappropriate, slightly appropriate, moderately appropriate, and highly appropriate areas are 1273.2 km² (44.69%); 906.1 km² (31.80%); 509.4 km² (17.88%); and 160.1 km² (5.62%), respectively. 3) The “deserting villages” in mountainous areas play positive synergistic roles in urbanization, in contrast to the “hollowing villages” common in plain areas. 4) The central town-village will become the most important settlement in mountainous areas. Therefore, we suggest more attention should be paid to environmental capacity in the construction of central town-villages. This study significantly extends the understanding of “hollowing village” theory and regional planning.  相似文献   

Assessing climate change impacts on the Iberian power system using a coupled water-power model   总被引：1，自引：1，他引：0  

Silvio J. Pereira-Cardenal  Henrik Madsen  Karsten Arnbjerg-Nielsen  Niels Riegels  Roar Jensen  Birger Mo  Ivar Wangensteen  Peter Bauer-Gottwein 《Climatic change》2014,126(3-4):351-364

Climate change is expected to have a negative impact on the power system of the Iberian Peninsula; changes in river runoff are expected to reduce hydropower generation, while higher temperatures are expected to increase summer electricity demand, when water resources are already limited. However, these impacts have not yet been evaluated at the peninsular level. We coupled a hydrological model with a power market model to study three impacts of climate change on the current Iberian power system: changes in hydropower production caused by changes in precipitation and temperature, changes in temporal patterns of electricity demand caused by temperature changes, and changes in irrigation water use caused by temperature and precipitation changes. A stochastic dynamic programming approach was used to develop operating rules for the integrated system given hydrological uncertainty. We found that changes in precipitation will reduce runoff, decrease hydropower production (with accompanying increases in thermal generation), and increase irrigation water use, while higher temperatures will shift power demand from winter to summer months. The combined impact of these effects will generally make it more challenging to balance agricultural, power, and environmental objectives in the operation of Iberian reservoirs, though some impacts could be mitigated by better alignment between temporal patterns of irrigation and power demands.  相似文献   

Surficial geology indicates early Holocene faulting and seismicity,central Sweden     

Colby A. Smith  Martin Sundh  Henrik Mikko 《International Journal of Earth Sciences》2014,103(6):1711-1724

In Sweden, knowledge of the location and timing of glacially induced faulting and seismicity is critical to effective engineering of a long-term nuclear disposal facility. To improve understanding and modeling of the complex ice-induced and tectonic stresses associated with glacially induced faulting, field studies detailing the location and timing of movement of such structures are required. Although the fault has not been confirmed in the bedrock, multi-proxy surficial geologic evidence indicates that the recently discovered scarp in Bollnäs is such a structure. Machine-excavated trenches across the scarp reveal landsliding down the scarp and, in one location, faulted and vertically offset fine-grained glacial sediments. The presence of water-escape structures in trenches excavated on a topographic high strongly suggests a co-seismic origin derived from earthquake magnitudes >5.5. Numerous landslides in till exist in the region as well. Four slopes with landslides were examined in detail, and the factors of safety for these slopes indicate stable conditions and suggest a seismic trigger. Basal radiocarbon dates from peat bogs located stratigraphically above the landslides provide minimum limiting ages for the co-seismic landslides. The oldest date indicates sliding prior to 10,180 calendar years before the present. The proposed Bollnäs Fault is 400 km south of the so called Lapland Fault Province. To date, it is the southernmost confirmed glacially induced fault in Sweden. The results of this study are consistent with existing modeling results that indicate fault instability in this region of central Sweden following deglaciation.  相似文献   

Upper Cretaceous bottom current deposits,north-east Greenland     

Jussi Hovikoski  Alfred Uchman  Rikke Weibel  Henrik Nøhr-Hansen  Emma Sheldon  Jon Ineson  Morten Bjerager  Jens Therkelsen  Mette Olivarius  Michael Larsen  Peter Alsen  Jørgen Bojesen-Koefoed 《Sedimentology》2020,67(7):3619-3654

Reported ancient bottom current deposits in deep marine settings are scarce and most of them remain contentious. This study describes sedimentological, ichnological and petrographical characteristics of a drill core that covers ca 10 Myr of Upper Cretaceous stratigraphy at Hold with Hope, north-east Greenland. The core is divided into four facies associations, which are interpreted to reflect deposition from bottom currents, turbidity flows and hemipelagic settling in slope and/or near slope environments. The evidence for bottom current influence is three-fold. Firstly, pervasive indications of winnowing such as marine bioclast-rich lags and outsized clasts on ‘mud on mud’ contacts are suggestive of low-sediment concentration flows capable of transporting up to pebble-sized clasts. Common Mn–Fe–Mg rich carbonate matrix cements and various types of hiatal chemogenic lag deposits showing glauconite, apatite and carbonate clasts also point to condensation, prolonged exposure at the sediment–water interface and recurrent phases of sea-floor erosion. Secondly, such deposits can show indicators for tidal processes such as double mud-drapes, tangential bottom sets in dune-scale cross-bedding and cyclic rhythmites. Thirdly, inverse to normal grading at various scales is common in fully marine, commonly seafloor-derived sediments. Ichnological data indicate considerable taxonomic variability in the bottom current deposits, but recurrent fabrics are characteristically dominated by morphologically simple burrows such as Thalassinoides and Planolites, with secondary Phycosiphon, Nereites, Zoophycos and/or Chondrites. In general, opportunistic taxa are common whereas mature composite ichnofabrics are rare. The omission surfaces are locally burrowed with stiffground to firmground trace fossil suites. The results contribute to establishing sedimentological, ichnological and mineralogical criteria for recognition of bottom current deposits as well as to the understanding of the Late Cretaceous palaeoenvironmental evolution of the Arctic region.  相似文献   

Geological evolution,regional perspectives and hydrocarbon potential of the northwest Phu Khanh Basin,offshore Central Vietnam     

Michael B.W. Fyhn  Lars H. Nielsen  Lars O. Boldreel  Le D. Thang  Jørgen Bojesen-Koefoed  Henrik I. Petersen  Nguyen T. Huyen  Nguyen A. Duc  Nguyen T. Dau  Anders Mathiesen  Ian Reid  Dang T. Huong  Hoang A. Tuan  Le V. Hien  Hans P. Nytoft  Ioannis Abatzis 《Marine and Petroleum Geology》2009

Seismic stratigraphic and structural analyses of the northwest Phu Khanh Basin, offshore Central Vietnam, based on 2-D seismic data, indicate that the initial rifting began during the latest Cretaceous? or Palaeogene controlled by left-lateral transtension along the East Vietnam Boundary Fault Zone (EVBFZ) and northwest–southeast directed extension east of the EVBFZ. Rifting stopped due to transpression during middle Oligocene times but resumed by left-lateral transtension during the Late Oligocene. Thick sequences of lacustrine and alluvial sediments were deposited during the Palaeogene rift periods. The Late Oligocene rifting ended due to inversion, triggered by right-lateral wrenching near the Palaeogene–Neogene boundary. Following the onset of this inversion regional uplift and volcanism took place in the southern half of the study area and contemporaneous subsidence and transgression took place farther north, leading to widespread carbonate deposition. As the right-lateral wrenching decreased during the early Neogene, thermal subsidence and siliciclastic sedimentation became dominant, resulting in the buildup and southward propagation of the shelf slope. Sediment accumulation and subsidence rates increased after the Middle Miocene times due to eastward tilting of Central Vietnam and the adjacent offshore area.  相似文献