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1.
The Kerio valley lies between the Elgeyo escarpment and the Tugen hills which mark the western margin of the Kenya rift valley. The main fluorite deposits are located in the southern part of the valley at Kimwarer, Choff and Kamnaon.Three types of inclusion fillings were identified: Liquid+Vapour, Liquid+Daughter Minerals and Liquid. The L+V type is dominant. Inclusions occur as clusters, trails along the crystal growth zones and as isolated ones. Low salinities, apparently lower than the 5% wt. NaCl equivalent, were established. Homogenization temperatures suggest that fluorite mineralization took place at different stages and at temperatures between 120 and 180 °C. Isolated readings above 180°C may be referring to the original inclusions in limestone. These measurements and the absence of CO2 in the inclusions, as well as the occurrence of vugs and crustifications with fluorite, suggest that mineralization took place at relatively shallow depths.Emission spectrum lines representing Eu2+, Dy3+, Tb3+ and Sm3+ in fluorite were identified. Sm3+ was detected only in the pinkish luminescence of veined fluorite, whereas the pinkish zone in banded fluorite contains Tb3+. Eu2+ which gives the strongest emission lines in the blue part of the visible spectrum, apparently is responsible for the strong blue cathodoluminescence (CL) in fluorite. The dominance of Eu2+ peaks further points to the fact that fluorite mineralization in the Kerio valley took place in an environment that was enriched in Lanthanide Rare Earth Elements (LREE). The presence of rare earths and radioactive elements in fluorite points towards their enrichment in the environment of fluorite mineralization. A juvenile origin of mineral forming solutions is proposed.Two generations of fluorite were established: allotriomorphic fluorite, forming the matrix, and the idiomorphic variety, occurring either in barite or in druzes in early fluorite. Barite in turn forms idiomorphic crystals in allotriomorphic fluorite. Relics of calcite occur in both K-feldspars and in early fluorite. Oxides and hydroxides of Fe, Mn, Ti and Al commonly occur in open spaces in fluorite. Of significance is the presence of gold in fluorite. Fluorite mineralization is of hydrothermal origin in the post-Miocene era and was formed as a result of metasomatic replacement of marble and open space fillings. 相似文献
2.
This project was conducted to investigate the breakage and fallout behaviour of various types of architectural glass elements in a dry-glazed curtain wall system under in-plane and out-of-plane dynamic motions. The project was a follow-up to an earlier project that focused exclusively on in-plane dynamic racking performance of curtain wall glass elements. The recent data indicated that adding out-of-plane motions caused significantly higher amounts of glass breakage and subsequent glass fallout in most glass types that were found during the in-plane tests to be prone to glass fallout. Specifically, 1/4 in (6 mm) annealed monolithic glass, 1/4 in annealed monolithic glass with a 0·004 in (0·10 mm) PET film (not anchored to the mullions), and 7/16 in (11 mm) fully tempered laminated glass exhibited comparable or higher fallout rates than the already substantial fallout rates that were observed during the in-plane only racking tests. Unanchored window film was found to be ineffective in resisting post-breakage glass fallout under dynamic racking motions. In contrast, 1/4 in (6 mm) annealed laminated glass and 7/16 in (11 mm) heat-strengthened laminated glass exhibited no glass fallout during the out-of-plane tests, just as they exhibited no fallout during the in-plane tests. Out-of-plane test results also showed that 3/8 in (10 mm) heat-strengthened monolithic glass exhibited no fallout, while 3/8 in annealed monolithic glass exhibited very negligible glass fallout. The addition of torsional motions was not found to induce glass fallout in those glass types that resisted glass fallout in previous tests performed without torsional motions. 相似文献
3.
ZusammenfassungEinige Geräte und Techniken für die Rationalisierung gefügestatistischer Arbeiten bei tektonischen und felsmechanischen Untersuchungen Eine bedeutende Rationalisierung großzahlstatistischer Messungen von Gefügeelementen, die als Unterlage für felsmechanische und tektonische Untersuchungsarbeiten erforderlich sind, wird mit Hilfe einiger neu entwickelter Geräte und Auswertungstechniken erreicht. Für Kompaßmessungen findet ein Gelände-Registriergerät Verwendung, mit welchem Lochdiagramme angefertigt werden. Ein halbautomatischer Universaldrehtisch erlaubt die selbsttätige Registrierung mikroskopischer Gefügemessungen, die ebenfalls in Lochdiagrammen Aufnahme finden. Über ein photomechanisches Verfahren werden die Lochdiagramme in Konturen-Diagramme übergeführt.
Mit 3 Abbildungen 相似文献
SummarySome Devices and Techniques for Rationalization of Statistical Measurements of Fabric Elements in Tectonic and Rock Mechanical Investigations A considerable rationalization of large-number statistical measurements of fabric elements, necessary as basis for research work in rock mechanics and tectonics, is obtained with the aid of some recently developed instruments and evaluation techniques. For compass measurements a field recording device is used, with which punch diagrams are made. A semiautomatic universal stage enables the automatic recording of microscopic fabric measurements, which are also recorded by punch diagrams. These diagrams are transformed into contour diagrams by a photomechanical procedure.
RésuméQuelques appareils et techniques pour rationaliser les travaux de statistique structurale aux recherches tectoniques et de mécanique des roches Une rationalisation considérable de mesurages statistiques sur grandes nombres d'éléments de texture nécessaire comme base pour des recherches de la mécanique de roches et de la tectonique, est obtenue à l'aide de quelques instruments et de procédés d'évaluation récemment développés. Pour les mesurages exécutés avec la boussole on se sert d'un enregistreur de terrain avec lequel des diagrammes de perforation sont faits. Une table tournante universelle semi-automatique permet l'enregistrement automatique de mesurages microscopiques de la structure qui sont enregistrés également par les diagrammes de perforation. A l'aide d'un procédé photomécanique ces diagrammes de perforation sont transformés en diagrammes de contour.
Mit 3 Abbildungen 相似文献
4.
Jennifer Hauxwell James McClelland Peter J. Behr Ivan Valiela 《Estuaries and Coasts》1998,21(2):347-360
Macroalgal biomass and competitive interactions among primary producers in coastal ecosystems may be controlled by bottom-up processes such as nutrient supply and top-down processes such as grazing, as well as other environmental factors. To determine the relative importance of bottom-up and top-down processes under different nutrient loading conditions, we estimated potential amphipod and isopod grazer impact on a dominant macroalgal species in three estuaries in Waquoit Bay, Cape Cod, Massachusetts, that are subject to different nitrogen loading rates. We calculated growth increases and grazing losses in each estuary based on monthly benthic survey data of macrophyte biomass and herbivore abundance, field grazing rates of amphipods (Microdeutopus gryllotalpa andCymadusa compta) and an isopod (Idotea baltica) on the preferred and most abundant macroalga (Cladophora vagabunda) and laboratory grazing rates for the remaining species, and in situ macroalgal growth rates. As nitrogen loading rates increased, macroalgal biomass increased (3×), eelgrass (Zostera marina) was lost, and herbivore abundance decreased (1/4×). Grazing rates increased with relative size of grazer (I. baltica > C. compta > M. gryllotalpa) and, for two of the three species investigated, were faster on algae from the high-nitrogen estuary in comparison to the low-nitrogen estuary, paralleting the increased macroalgal tissue percent nitrogen with nitrogen load. Macroalgal growth rates increased (2×) with increasing nitrogen loading rate. The comparison between estimated growth increases versus losses ofC. vagabunda biomass to grazing suggested first, that grazers could lower macroalgal biomass in midsummer, but only in estuaries subject to lower nitrogen loads. Second, the impact of grazing decreased as nitrogen loading rate increased as a result of the increased macroalgal growth rates and biomass, plus the diminished abundance of grazers. This study suggests the relative impact of top-down and bottom-up controls on primary producers varies depending on rate of nitrogen loading, and specifically, that the impact of herbivory on macroalgal biomass decreases with increasing nitrogen load to estuaries. 相似文献
5.
A model of the cooling history of tin-bearing granitic magma forming the Schellerhau granites (Eastern Erzgebirge, Germany)
is shown on the basis of quartz textures. Similar grain size, similar grain habit and correlatable growth textures of phenocrysts
in different granite varieties give proof of a common crystallization history before the melts of the Schellerhau granite
varieties were intruded. Four nucleation events occurred during crystallization in different crustal levels between about
20 and 1 km depth. The parental melt of the Schellerhau granites is interpreted to have contained<2.5 wt% H2O originally. The water content of the melt during the subvolcanic intrusion stage amounted to more than 5 wt% and characterizes
highly evolved residual melts that enable the formation of tin deposits. This study contributes to a better understanding
of the development and behaviour of fractionated tin-bearing granitic melts, and links quartz cathodoluminescence (CL) with
microanalytical studies.
Received: 28 October 1998 / Accepted: 18 August 1999 相似文献
6.
7.
We present measurements of electric fields in quiescent prominences and in a small flare surge, obtained with the CRI electrograph at the NSO/SP 40 cm coronagraph, in 1993 and 1994. Our results on the 9 brightest quiescent prominences enable us to place r.m.s. upper limits ofE
t < 2 – 5 V cm–1 on the component ofE transverse to the line of sight. We show that these upper limits may be difficult to reconcile with non-ideal MHD models of quiescent prominences formed in extended neutral sheets, whether or not the tearing mode instability is present. They do, however, seem consistent with ideal MHD models of prominence support. We point out also that these upper limits are within a factor 4 of the minimum value of anistropic electric field that exists due to motional Stark effect in any thermal plasma permeated by a directed magnetic field.Our data on the flare surge suggest an electric field of intensityE 35 V cm–1, oriented approximately parallel to the inferred magnetic field. This detection ofE
needs to be verified in other flares. But we note that a detectableE
would not be expected in the current interruption flare mechanism, if only a single double layer is present. We show further that the observed relatively narrow, approximately-Gaussian, and only slightly Doppler-shifted Paschen lines, seem inconsistent with the multiple double layers invoked in other models based on the current interruption mechanism. Our detection ofE
does seem consistent with reconnection (including tearing-mode) models of flares, provided the field-aligned electrical conductivity is anomalous over substantial volumes of the plasma circuit joining the reconnecting domain to the photosphere. 相似文献
8.
D. Pomarde P. J. Boyle M. Urban H. M. Badran L. Behr M. T. Brunetti D. J. Fegan T. C. Weekes 《Astroparticle Physics》2001,14(4)
The antimatter research through the earth moon ion spectrometer (ARTEMIS) experiment is described in terms of searching for the moon's shadow in the primary cosmic radiation at TeV energies. Observations were made using the Whipple 10 m Imaging Atmospheric
erenkov Telescope, in conjunction with a special optical filter to suppress unwanted moonlight. Monte Carlo simulations were used to predict that the magnitude of shadowing based on a pure proton beam would be 1% of the cosmic ray background. Observations and event classification are discussed, and results of a search for shadowing based on both protons and antiprotons are presented. Atmospheric fluctuations giving rise to non-statistical event rates constituted a limiting factor to the sensitivity of the shadow search as they rivaled or exceeded statistical errors. It is demonstrated that the experiment does not have sufficient sensitivity to moon shadowing which would allow a search for an antimatter component in the primary cosmic ray flux at the percent level. Possible future improvements of the technique are discussed. 相似文献
9.
Daiani Kochhann Everton Rodolfo Behr Adilson de Chaves Marcia F. Mesko Valderi L. Dressler Erico M. M. Flores Bernardo Baldisserotto 《Environmental Earth Sciences》2013,70(4):1727-1733
The water quality of the Vacacaí River was assessed at different sites in the period between winter 2005 and autumn 2006. All samples were analyzed for 52 elements (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Li, Be, Mg, Al, Ca, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, In, Cs, Ba, Tl, Pb, Bi, U, Na, K, Hg, B, Mo, Sn, Te, Ti), temperature, pH, ammonia, and alkalinity levels. Water from the Vacacaí River ranged from slightly acidic to alkaline. No difference was observed in the chemical composition at different sites of the Vacacaí River. Levels of Ba, Ca, Sr and Mg increase in the dry seasons and reach their highest concentrations in autumn; Be and U decrease in the dry season and reach their highest concentration in spring. Al, Fe, Cr, Ni, Th, U Mn, Ca and Mg are highly positively related, indicating a common origin. Se and Cu are probably from anthropogenic source, from the rice crops of the margins of the river. Waterborne Al and Fe levels were above the desirable level for drinking water at all sites during all seasons. These results demonstrate the need for constant monitoring of water parameters, which is crucial to ensure water quality for the population of this region. 相似文献
10.
Carlo?CauzziEmail author Yannik?Behr Thomas?Le?Guenan John?Douglas Samuel?Auclair Jochen?Woessner John?Clinton Stefan?Wiemer 《Bulletin of Earthquake Engineering》2016,14(9):2495-2512
Based on our experience in the project REAKT, we present a methodological framework to evaluate the potential benefits and costs of using earthquake early warning (EEW) and operational earthquake forecasting (OEF) for real-time mitigation of seismic risk at nuclear facilities. We focus on evaluating the reliability, significance and usefulness of the aforementioned real-time risk-mitigation tools and on the communication of real-time earthquake information to end-users. We find that EEW and OEF have significant potential for the reduction of seismic risk at nuclear plants, although much scientific research and testing is still necessary to optimise their operation for these sensitive and highly-regulated facilities. While our test bed was Switzerland, the methodology presented here is of general interest to the community of EEW researchers and end-users and its scope is significantly beyond its specific application within REAKT. 相似文献