Sur la présence de nickel dans un gisement de bauxite près de Mégare     

G. de Weisse 《Mineralium Deposita》1967,2(4):349-356

Résumé L'exploitation récente d'un gisement de bauxite près de Mégare (Grèce) a fait apparaître sur les calcaires de base une concentration verte d'oxyde de nickel relativement élevée. La présence dans le gisement d'argiles rouges, renfermant de fortes proportions d'oxyde de fer avec des teneurs relativement faibles en alumine et des traces d'oxyde de nickel, induit à penser qu'il s'agit d'un produit latéritique dérivé d'une roche ultrabasique et transporté ultérieurement sur la région calcaire karstifiée avec ses remplissages bauxitiques. L'étude se termine par une hypothèse sur la genèse de ce gîte singulier.

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The recent mining of a bauxite deposit near Megara (Greece) has shown on the footwall limestone a relatively high concentration of a green nickel oxide. The occurrence in the same deposit of red clays with a rather high percentage of iron oxide and a low content of alumina, together with some traces of nickel, induces to think that this material is composed of a lateritic soil derived from an ultrabasic rock and subsequently transported on karstified limestone with its bauxitic fillings. — The study ends with an hypothesis on the genesis of this unusual deposit.

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Identification of chlorite and chlorite-related minerals in sediments     

H. W. van der Marel 《Contributions to Mineralogy and Petrology》1964,9(5):462-480

A scheme is presented for the identification and classification of chlorite and related minerals in sediments which is mainly based on X-ray characteristics of the orginal sample and the sample heated at 350°C and treated with K⁺ and with glycerol. Examples are given. It is emphasized that additional data about clay mineral genesis, electron microscopy, infrared spectroscopy and chemical analyses are needed for the ordening of a certain mineral in the proposed scheme. Many names of minerals so far found to occur in the clay separate of sediments proved to be synonymous (52 of a total of 88) and thus should be abandoned. They only give confusion and needlessly increase the many difficulties which already exist in the identification, classification and quantitative determination of this complicated group of minerals of about 36 well defined specimens which may be found in sediments.  相似文献   

An optimized method for automated analysis of algal pigments by HPLC   总被引：3，自引：0，他引：3  

M.A. van Leeuwe  L.A. Villerius  J. Roggeveld  R.J.W. Visser  J. Stefels 《Marine Chemistry》2006,102(3-4):267-275

A recent development in algal pigment analysis by high-performance liquid chromatography (HPLC) is the application of automation. An optimization of a complete sampling and analysis protocol applied specifically in automation has not yet been performed. In this paper we show that automation can only be successful if the various methodological aspects of the sampling and analysis protocol are considered in coherence. We introduce an optimized protocol that involves freeze-drying of the sample, subsequent extraction in 90% acetone and the application of water-packing during analysis. The method was evaluated on both natural plankton populations and a broad spectrum of microalgal cultures: Thalassiosira weisflogii (Bacillariophyceae), Emiliania huxleyi (Prymnesiophyceae), Phaeocystis globosa and Phaeocystis antarctica (Prymnesiophyceae) and Pyramimonas sp. (Prasinophyceae). Whereas pigment extracts were unstable in methanol, with recorded chlorophyll a losses from 10% to 60% per day, pigment degradation rates in acetone were generally less than 1% over 18 h storage in the autosampler (4 °C). In addition, it was found that the extraction efficiency of acetone significantly increased upon freeze-drying prior to extraction. Increases as high as 50–60% were measured in P. antarctica. The application of water-packing of the sample during injection resulted in improved peak shape and peak separation, without diluting the pigment concentrations. Automation is especially beneficial for application in the field, when mixed algal assemblages and low biomass put a high demand on the sensitivity as well as reproducibility of the method.  相似文献   

Longitudinal strength of a high-speed ferry     

T.E. Schellin  A.Perez de Lucas   《Applied Ocean Research》2004,26(6):298-308

The longitudinal strength of the high-speed ferry was investigated by subjecting the ship's hull girder to long-term loads obtained from a frequency-domain panel code. Prior to the statistical analysis, linearly computed transfer functions were corrected for nonlinear effects, yielding two sets of transfer functions valid for different wave amplitudes. One set corresponded to the hogging condition; the other set, to the sagging condition. Two regular equivalent design waves were specified that resulted in loads representing the most severe global design load conditions. The still-water loading condition, yielding a still-water vertical bending moment in hogging, was superimposed on the wave-induced loads to obtain the total (design) loads in hogging. For the sagging condition only, additional impact-related loads were superimposed to obtain the total (design) loads in sagging. A finite element model of the ship's structure was subjected to pressure distributions according to the two regular design waves. For comparison with classification society rule values, a simple beam theory strength analysis of the ship's midship section was performed first, and then another finite element analysis was carried out, whereby the imposed loads were tuned to the rule values of vertical bending moments. Rule-based magnitudes of nominal maximum longitudinal stress deviated significantly (25–39%) from comparable stresses obtained by the panel code based finite element analysis. However, stresses obtained from the rule-based finite element analysis agreed more favorably, especially in hogging. In the uppermost deck, for example, the panel code based compressive stress was only 9% larger than the comparable stress from the rule-based finite element analysis.  相似文献   

Quaternary geology of the Amazonian Lowland     

Georg Irion  Jens Müller  Jose Nunes de Mello  Wolfgang J. Junk 《Geo-Marine Letters》1995,15(3-4):172-178

The Quaternary history of the Amazon lowlands is characterized by deposition of sediments of Andean provenance and by the influences of changing sea levels. Areas well above the present water tables were not reached by Pleistocene high-water stages. These areas have been intensively weathered since the Tertiary, forming hard lateritic weathering horizons. These weathering horizons are best explained by the relatively constant, humid tropical climate throughout the Quaternary. In the western Amazonian Lowland, flood plains corresponding to the different Pleistocene sea-level heights were formed. During low sea level, erosion in the drainage areas increased and the water levels of the central Amazon River system were lowered. Valleys drowned and lakes formed in the lower reaches of rivers and creeks during high sea-level stages. These lakes (ria lakes) remained in the valleys with rivers having a low sediment load. Seismic profiling (3.5 kHz) in some of these lakes clearly showed deposits of the three last periods of Quaternary high sea-level stages.  相似文献   

Submarine canyon development in the Izu-Bonin forearc: A SeaMARC II and seismic survey of Aoga Shima Canyon     

Adam Klaus  Brian Taylor 《Marine Geophysical Researches》1991,13(2):131-152

SeaMARC II sidescan (imagery and bathymetry) and seismic data reveal the morphology, sedimentary processes, and structural controls on submarine canyon development in the central Izu-Bonin forearc, south of Japan. Canyons extend up to 150 km across the forearc from the trench-slope break to the active volcanic arc. The canyons are most deeply incised (1200–1700 m) into the gentle gradients (1–2°) upslope on the outer arc high (OAH) and lose bathymetric expression on the steep (6–18°) inner trench-slope. The drainage patterns indicate that canyons are formed by both headward erosion and downcutting. Headward erosion proceeds on two scales. Initially, pervasive small-scale mass wasting creates curvilinear channels and pinnate drainage patterns. Large-scale slumping, evidenced by abundant crescent-shaped scarps along the walls and tributaries of Aoga Shima Canyon, occurs only after a channel is present, and provides a mechanism for canyon branching. The largest slump has removed >16 km³ of sediment from an 85 km² area of seafloor bounded by scarps more than 200 m high and may be in the initial stages of forming a new canyon branch. The northern branch of Aoga Shima Canyon has eroded upslope to the flanks of the arc volcanoes allowing direct tapping of this volcaniclastic sediment source. Headward erosion of the southern branch is not as advanced but the canyon may capture sediments supplied by unconfined (non-channelized) mass flows.Oligocene forearc sedimentary processes were dominated by unconfined mass flows that created sub-parallel and continuous sedimentary sequences. Pervasive channel cut-and-fill is limited to the Neogene forearc sedimentary sequences which are characterized by migrating and unconformable seismic sequences. Extensive canyon formation permitting sediment bypassing of the forearc by canyon-confined mass flows began in the early Miocene after the basin was filled to the spill points of the OAH. Structural lows in the OAH determined the initial locus of canyon formation, and outcropping basement rocks have prevented canyon incision on the lower slope. A major jog in the canyon axis, linear tributaries, and a prominent sidescan lineament all trend NW-NNW, reflecting OAH basement influence on canyon morphology. This erosional fabric may reflect joint/fracture patterns in the sedimentary strata that follow the basement trends. Once the canyons have eroded down to more erosion-resistant levels, channel downcutting slows relative to lateral erosion of the canyon walls. This accounts for the change from a narrow canyon axis in the thickly sedimented forearc basin to a wider, more rugged canyon morphology near the OAH. About 9500 km³ of sediment has been eroded from the central, 200 km long, segment of the Izu-Bonin forearc by the formation of Aoga Shima, Myojin Sho and Sumisu Jima canyons. The volume of sediment presently residing in the adjacent trench, accretionary wedge, and lower slope terrace basin accounts for <25% of that eroded from the canyons alone. This implies that a large volume (>3500 km³ per 100 km of trench, ignoring sediments input via forearc bypassing) has been subducted beneath the toe of the trench slope and the small accretionary prism. Unless this sediment has been underplated beneath the forearc, it has recycled arc material into the mantle, possibly influencing the composition of arc volcanism.  相似文献   

Paleoenvironment and sea-level change in the early Cretaceous Barents Sea—implications from near-shore marine sapropels     

Uwe?LangrockEmail author  Ruediger?Stein  Marcus?Lipinski  Hans-Jürgen?Brumsack 《Geo-Marine Letters》2003,23(1):34-42

The late Volgian (early "Boreal" Berriasian) sapropels of the Hekkingen Formation of the central Barents Sea show total organic carbon (TOC) contents from 3 to 36 wt%. The relationship between TOC content and sedimentation rate (SR), and the high Mo/Al ratios indicate deposition under oxygen-free bottom-water conditions, and suggest that preservation under anoxic conditions has largely contributed to the high accumulation of organic carbon. Hydrogen index values obtained from Rock-Eval pyrolysis are exceptionally high, and the organic matter is characterized by well-preserved type II kerogen. However, the occurrence of spores, freshwater algae, coal fragments, and charred land-plant remains strongly suggests proximity to land. Short-term oscillations, probably reflecting Milankovitch-type cyclicity, are superimposed on the long-term trend of constantly changing depositional conditions during most of the late Volgian. Progressively smaller amounts of terrestrial organic matter and larger amounts of marine organic matter upwards in the core section may have been caused by a continuous sea-level rise.  相似文献   

赤潮生物种类特征光谱获取技术   总被引：1，自引：0，他引：1  

范学炜  张汉德 《海洋科学进展》2002,20(2):83-90

较为系统地研究了赤潮生物水体反射率曲线获取方法。通过对 2类反射率反演方法得出的反射率曲线与实际反射率曲线进行比较 ,得出在不具备大气环境参数的情况下 ,经验线性法的反演结果与实际反射率曲线最接近的结论 ,并进一步对正常海水和赤潮生物水体的光谱特性进行分析 ,提取出赤潮生物水体的特征光谱。这是进行赤潮监测和识别的重要前提  相似文献   

Trends in biomass, density and diversity of North Sea macrofauna   总被引：6，自引：2，他引：6  

Heip  C.; Basford  D.; Craeymeersch  J. A.; Dewarumez  J. M.; Dorjes  J.; de Wilde  P.; Duineveld  G.; Eleftheriou  A.; Herman  P. M. J.; Niermann  U.; Kingston  P.; Kunitzer  A.; Rachor  E.; Rumohr  H.; Soetaert  K.; Soltwedel  T. 《ICES Journal of Marine Science》1992,49(1):13-22

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A quantitative evaluation of the impact of beam trawling on benthic fauna in the southern North Sea     

Piet  G. J.; Rijnsdorp  A. D.; Bergman  M. J. N.; van Santbrink  J. W.; Craeymeersch  J.; Buijs  J. 《ICES Journal of Marine Science》2000,57(5):1332-1339

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