Effective resource estimates for primary diamond deposits from the EKATI Diamond Mine™, Canada

Primary economic diamond deposit modelling has rarely been documented in the public domain. This paper presents information collected from significantly diamondiferous kimberlite pipes located near Lac de Gras in the Arctic region of Canada's Northwest Territories. The resource estimation process is widely accepted as a cyclical iteration of data collection and evaluation processes. A resource database is typically assembled from a large inventory of exploration data. These data must be methodically quality checked before accepting the information for interpretive analysis. The foundation of a mineral resource model is based on clear understanding of the geology model along with subsidiary grade, volume, and density models. Defining these models is an iterative process of statistical analyses and interpretation. As a deposit progresses along a path towards development, reducing risk to acceptable levels is critical for identifying and realizing its maximum value.     

The Barents Sea Ice Sheet — A model of its growth and decay during the last ice maximum

On the basis of geomorphological and sedimentological data, we believe that the entire Barents Sea was covered by grounded ice during the last glacial maximum. ¹⁴C dates on shells embedded in tills suggest marine conditions in the Barents Sea as late as 22 ka BP; and models of the deglaciation history based on uplift data from the northern Norwegian coast suggest that significant parts of the Barents Sea Ice Sheet calved off as early as 15 ka BP. The growth of the ice sheet is related to glacioeustatic fall and the exposure of shallow banks in the central Barents Sea, where ice caps may develop and expand to finally coalesce with the expanding ice masses from Svalbard and Fennoscandia.The outlined model for growth and decay of the Barents Sea Ice Sheet suggests a system which developed and existed under periods of maximum climatic deterioration, and where its growth and decay were strongly related to the fall and rise of sea level.     

Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 m equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 m EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K₂SO₄,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine.     

Capture-zone design in an aquifer influenced by cyclic fluctuations in hydraulic gradients

Design of a groundwater pumping and treatment system for a wood-treatment facility adjacent to the tidally influenced Fraser River estuary required the development of methodologies to account for cyclic variations in hydraulic gradients. Design of such systems must consider the effects of these cyclic fluctuations on the capture of dissolved-phase contaminants. When the period of the cyclic fluctuation is much less than the travel time of the dissolved contaminant from the source to the discharge point, the hydraulic-gradient variations resulting from these cycles can be ignored. Capture zones are then designed based on the average hydraulic gradient determined using filter techniques on continuous groundwater-level measurements. When the period of cyclic fluctuation in hydraulic gradient is near to or greater than the contaminant travel time, the resulting hydraulic-gradient variations cannot be ignored. In these instances, procedures are developed to account for these fluctuations in the capture-zone design. These include proper characterization of the groundwater regime, assessment of the average travel time and period of the cyclic fluctuations, and numerical techniques which allow accounting for the cyclic fluctuations in the design of the capture zone. Electronic Publication     

A discontinuous finite element suspended sediment transport model for water quality assessments in river networks

Suspended sediment plays an important role in the distribution and transport of many pollutants (such as radionuclides) in rivers. Pollutants may adsorb on fine suspended particles (e.g. clay) and spread according to the suspended sediment movement. Hence, the simulation of the suspended sediment mechanism is indispensable for realistic transport modelling. This paper presents and tests a simple mathematical model for predicting the suspended sediment transport in river networks. The model is based on the van Rijn suspended load formula and the advection–diffusion equation with a source or sink term that represents the erosion or deposition fluxes. The transport equation is solved numerically with the discontinuous finite element method. The model evaluation was performed in two steps, first by comparing model simulations with the measured suspended sediment concentrations in the Grote Nete–Molse Nete River in Belgium, and second by a model intercomparison with the sediment transport model NST MIKE 11. The simulations reflect the measurements with a Nash‐Sutcliffe model efficiency of 0.6, while the efficiency between the proposed model and the NST MIKE 11 simulations is 0.96. Both evaluations indicate that the proposed sediment transport model, that is sufficiently simple to be practical, is providing realistic results.     

Uranium prospecting with Rn in frozen terrain

Published reports show that ²²²Rn contents of soil gas can increase under snow-covered or frozen soils. By utilizing these observations and results of field tests described here, it can be stated that U prospecting with ²²²Rn in frozen terrain is practicable.Rn profiles in frozen and snow-covered soils over U mineralization in the Bancroft area of Ontario outlined known radioactive zones more clearly than did scintillometer profiles.Tests in Gatineau Park, Quebec, in the proximity of a radioactive pegmatite dike showed that lake ice acts as a restrictive barrier to Rn movement from lake waters beneath. Water samples, collected and allowed to freeze in plastic bottles, retained dissolved Rn quite effectively thus permitting sample collection and storage under the most severe winter conditions. Rn sampling of through-ice lake waters is therefore a feasible prospecting tool.Samples of spring run-off (snow-melt) waters and slushy snow collected from within a known weakly radioactive zone near South March, Ontario, were shown to contain less Rn than found in the same stream waters in the summer. No pronounced Rn degassing event of frozen soils was apparent early in the spring thaw in percolating run-off waters draining from the zone. The usefulness of spring thaw hydrogeochemistry using Rn is discussed.     

Geophysikalische Einflüsse auf die Länge des Sterntages

Zusammenfassung Die Änderung der Sterntaglänge schwankt im Rhythmus des Luftdruckgefälles zwischen 45 und 65° Süd sowohl im mittleren Jahresgang als auch im Ablauf der sechzig Monate der Jahre 1957–1961. Dieser überzufällige Gleichgang in Phase und Amplitude läßt sich so erklären, daß die Schwankungen der Tageslänge direkt durch den Schub oder die Bremsung der Lithosphäre, auf welche die Atmosphäre mit ihren Monsunen oder Passaten wirkt, erzeugt werden. Die den schwankenden Tropenwinden parallel gehenden außertropischen Westwinde würden voll die schiebende oder bremsende Wirkung der Tropenwinde kompensieren, wenn sie auch direkt die Lithosphäre erfaßten. Da nun aber im Gebiet der braven Westwinde die Hydrosphäre den gesamten Drehimpuls übernimmt und ihn wohl erst mit großer Verzögerung an die Lithosphäre weiterreicht, tritt die Änderung der Tageslänge auf, die sich im wesentlichen harmonisch aus einer halbjährlichen und einer jährlichen Welle zusammensetzt.

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Geophysical effects on the length of the sideral day

Summary The variations in the length of the day are found to be equal in phase to the oscillation of the atmospheric pressure gradient occurring between 45 and 65 degrees south. This rhythm manifests itself in the annual mean as well as in the course of the 60 months of the years 1957 to 1961. The rhythm that seems to be overaccidental may be explained with regard to phase and amplitude in the following way:The variations in the length of the day are produced by the pushing or braking of the lithosphere on which the atmosphere is acting by its monsoons or trade winds. The outertropical westerlies that are blowing parallel to the tropical wind would be able to compensate the pushing and braking effects if they, too, were directly acting on the lithosphere. As, however, in the region of the westerlies the hydrosphere assumes all angular momentum and apparently passes it on to the lithosphere after considerable delay, the variations in the length of the day are caused which essentially consist of the second and first harmonics.

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Effets géophysiques sur la longueur du jour sidéral

Résumé Les variations de la longueur du jour sidéral suivent le rythme du gradient de pression atmosphérique rencontré entre le 45^e et 65^e degré de latitude Sud. Elles se manifestent dans la moyenne annuelle aussi bien que dans la période des soixants mois des années de 1957 à 1961. Cette homogénéité super-aléatoire du rythme qui se montre également dans la phase et dans l'amplitude pourrait être expliquée par le fait que les variations de la longueur du jour sidéral sont directement produites par la poussée et le freinage de la lithosphère sur lequel agit l'atmosphère par ses moussons et ses vents alizés.Les vents extra-tropicaux d'ouest qui soufflent parallèlement aux vents tropicaux seraient à même de compenser les effets de la poussée et du freinage des vents tropicaux pourvu qu'ils agissent de même immédiatement sur la lithosphère. Comme, cependant, dans la région des braves vents d'ouest l'hydrosphère attire tout le moment angulaire et le passe, probablement après un long délai, au lithosphère, il se produit les variations de longueur du jour sidéral, qui se composent essentiellement d'une oscillation harmonique semestrielle et annuelle.

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Nach einem Vortrag Über Erddrehung und atmosphärische Globalzirkulation vor dem Geophysikalischen Kolloquium der Universität Hamburg am 8. Juni 1961, erweitert um die neuen Daten der Tageslänge und des Luftdruckgefälles zwischen 45° und 65° S.     

Les Diatomées de la Tourbière du Cachot (Jura neuchâtelois)

By means of 18 traps, 124 species (including 4 fossil ones) with a total of 3.5×10⁵ cells/m² have been identified an determined as transported by wind. 119 species have been detected on the feet and bills of waterbirds (Gallinago gallinago). Large migratory insects are capable of transporting diatoms over long distances, whereas small insects partake in the microdistribution. An average of 13.5 diatoms per insect (43 diatom species) were found on 44 insects.