Chemical variation in vesuvianite     

S. Fitzgerald  P. B. Leavens  J. A. Nelen 《Mineralogy and Petrology》1992,46(2):163-178

Summary Microprobeanalyses of 44 vesuvianite specimens of different color, morphology, and occurrence indicate the chemical variation of the species. Vesuvianites can be divided into four types, based on chemistry and color; most vesuvianites can be assigned to one of these types with confidence. Type 1 vesuvianites contain 2 atoms of Mg, <0.25 atoms of Ti, and variable Fe, apparently trivalent, in a formula based on 50 non-H cations. They are dark to pale green, white, or pink. Type 2 vesuvianites contain > 2.5 atoms of Mg, variable (divalent?) Fe, and <0.5 atoms of Ti. In color they are yellow, yellow-brown, or yellow-green. Type 3 vesuvianites contain divalent Fe, 0.5 to 1.5 atoms of Ti and close to 18 atoms of Si (full occupancy of tetrahedral sites). They are yellow, brown, red-brown, or black. Type 4 vesuvianites are manganoan or cuprian; the studied samples are from Pajsberg, Sweden, Franklin, New Jersey, and Telemark, Norway. In color they are red-brown, purple, blue (cyprine), or green. Iron and much of the Mn is apparently trivalent.Unlike garnets, which they resemble structurally, vesuvianites contain almost exclusively Ca in the eight-fold sites in the structure. Silicon occupies 95% or more of the tetrahedral sites. Aluminum fills the smaller octahedral site, A. Chemical variation occurs predominantly in the more open, octahedral, general or G site and in the five-coordinated B site. Simple substitutions in G include Fe³⁺ or Mn³⁺ for Al³⁺, and Fe²⁺, Mn²⁺, or Zn²⁺ for Mg²⁺. Coupled substitutions include TiO = AIOH, MgTi = AlAl and AlAl = MgSi. The B site may contain Cue²⁺, Fe²⁺, Fe³⁺, or A1³⁺. Changes in the amounts of O and OH in two different positions give a range of anion charge from 146 (0₆₇0H₁₂) to about 148 (0₆₉0H₁₀).

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Chemische variation in Vesuvianen

Zusammenfassung Mikrosondenanalysen von 44 Vesuvian-Proben, die in Farbe, Morphologie and Vorkommen unterschiedlich sind, zeigen die chemische Variation der Spezies. Aufgrund von Chemismus und Farbe können Vesuviane in vier Typen eingeteilt werden; die meisten Vesuviane konnen einem dieser Typen klar zugeordnet werden. Vesuviane vom Typ 1 enthalten in einer Formel, die sich auf 50 nicht-H Kationen bezieht, 2 Mg-Atome, < 0,25 Ti-Atome and variables, anscheinend dreiwertiges Fe. Sie sind dunkel- bis blaßgrün, weiß oder rosa. Vesuviane vom Typ 2 enthalten > 2,5 Mg-Atome, variables (zweiwertiges?) Fe and < 0,5 Ti-Atome. Sie sind gelb, gelbbraun oder gelbgrün gefärbt. Vesuviane vom Typ 3 enthalten zweiwertiges Fe, 0,5 bis 1,5 Ti-Atome and beinahe 18 Si-Atome (völlige Besetzung der Tetraederpositionen). Sie sind gelb, braun, rotbraun oder schwarz. Vesuviane vom Typ 4 sind Mangan- oder Kupfer-haltig; die untersuchten Proben sind von Pajsberg, Schweden, Franklin, New Jersey, and Telemark, Norwegen. Sie sind rotbraun, purpur, blau (Cyprin) oder grün gefarbt. Eisen und ein großer Teil des Mangns sind anscheinend dreiwertig.Im Unterschied zu den strukturell ähnlichen Granaten enthalten die Vesuviane auf den acht-koordinierten Positionen der Struktur fast nur Ca. Silizium besetzt 95% oder mehr der Tetraederpositionen. Aluminium füllt die kleinere Oktaederposition A. Chemische Variabilität tritt hauptsächlich in der offeneren, oktaedrischen, allgemeinen oder G Position and in der fiinf-koordinierten B Position auf. Einfache Substitutionen auf G umfassen Fe³⁺ und Mn³⁺ fur Al³⁺, sowie Fe²⁺, Mn²⁺ and Zn²⁺ für Mgt²⁺. Gekoppelte Substitutionen beinhalten TiO = AlOH, MgTi = AlAl and AlAl = MgSi. Die B Position kann Cu²⁺, Fe²⁺, Fe³⁺ and A1³⁺ enthalten. Wechsel in den Beträgen an O und OH auf zwei unterschiedlichen Positionen gibt für die Anionenladung einen Bereich von 146 (O₆₇OH₁₂) bis etwa 148 (O₆₉OH₁₀).[/p]

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Latitudinal changes in siphonophore assemblages across the Atlantic sector of the Southern Ocean     

D Kuyper  D Thibault  MJ Gibbons 《African Journal of Marine Science》2020,42(2):209-219

Siphonophores are commonly considered to be useful indicators of water masses and water-mass movement, but their employment as such across the wider Southern Ocean has not so far been attempted. We redress this here using archived samples, collected during January–February 1993 along a transect from Cape Town to the South African National Antarctic Expedition (SANAE) base in Antarctica, and compare the patterns generated with those determined from a prior analysis of whole assemblages at lower taxonomic resolution. Twenty-one species were identified from 18 of the original 53 samples collected, and two distinct assemblages were confirmed as separated by the Sub-Antarctic Front. That to the south was characterised by low diversity and high abundance and was dominated by cold-water specialists, whereas that to the north comprised a larger number of subtropical and temperate species at low abundance. Assemblage structure was strongly influenced by the mixed layer depth, sea surface salinity and chlorophyll a concentration, as well as mesozooplankton biomass. Congruence with the whole-assemblage study was high, indicating that this taxon can be suitably employed as a proxy in studies such as this. The study emphasises the value of archived plankton samples and makes a plea for better curation.  相似文献   

Quenching of phosphorus fixation with organic wastes in a bauxite mine overburden     

Vincent Fitzgerald Wright  Bryson Alando Brown  Mark Anglin Harris 《Environmental Earth Sciences》2011,63(3):469-476

Capabilities of two phosphate-rich organic wastes to quench phosphorus (P) fixation in a stored high-phosphorus-fixing tropical bauxite overburden were examined in a field experiment. Prior grinding and ensiling of shrimp shell waste facilitated increased solubility and hence phosphorus fixation quenching in the soil. Normal plant-available P concentrations were exhibited by the overburden for up to 4 months after application despite the cultivation and harvesting of plants in the treated beds. Ten-year-old, stored overburden treated with ensiled shrimp shell silage, or chicken manure exhibited P levels of 1.0 and 1.1%, respectively, 4 months after treatment application. This represents a small excess over normal concentrations of free P in the overburdens. These P levels dropped to 0.055 and 0.060%, respectively, after 8 months. The capacity of the soil to fix phosphorus was thus rapidly “filled” with an excess of P in the overburden. However, increased P fixation in the second 4-month period was attributed to the inherently high levels of Ca²⁺ in the ground. Therefore, amelioration based on quarterly applications promises a long-term corrective for P-fixing in stored bauxite overburdens.  相似文献   

Riverine influence determines nearshore heterogeneity of nutrient (C,N, P) content and stoichiometry in the KwaZulu-Natal Bight,South Africa     

UM Scharler  MJ Ayers  AM de Lecea  M Pretorius  ST Fennessy  JA Huggett 《African Journal of Marine Science》2016,38(1):S193-S203

Riverine influences on nearshore oceanic habitats often have detrimental consequences leading to algal blooms and hypoxia. In oligo- to mesotrophic systems, however, nutrient delivery via rivers may stimulate production and even be a vital source of nutrients, as may nutrient supplements from upwelling. We investigated the nutrient content (C, N, P) and stoichiometry of sediment, and several pelagic, benthopelagic and benthic species in the KwaZulu-Natal (KZN) Bight, a narrow shelf area on the south-east coast of South Africa, bordering the Agulhas Current. Three suggested nutrient sources to the bight are the Thukela River in the central region of the bight, upwelling in the northern part and a semi-permanent eddy (Durban Eddy) in the southern part. Elemental content of the various groups studied showed significantly higher values for most groups at the site near the Thukela River. C:P and N:P were highest in the southern part of the bight, and lowest near the Thukela Mouth or at Richards Bay in the north, indicating the latter were the P-richer sites. Sediment organic matter showed lowest elemental content, as expected, and zooplankton stoichiometry was highest compared to all other biotic groups. Environmental heterogeneity played a greater role in organismal C, N and P content and stoichiometry compared to phylogeny, with the exception of the differences in C:P and N:P of zooplankton. From this bight-wide study, the higher elemental content and lower ratios at the Thukela Mouth site supported previous findings of the importance of coastal nutrient sources to the bight ecosystem. Reductions in river flow for water use in the catchment areas may therefore have negative consequences for the productivity of the entire ecosystem.  相似文献   

Turbulent mixing in a stratified estuarine tidal channel: Hikapu Reach,Pelorus Sound,New Zealand     

CL Stevens  MJ Smith 《新西兰海洋与淡水研究杂志》2016,50(4):485-505

Channel constrictions within an estuary can influence overall estuary-sea exchange of salt or suspended/dissolved material. The exchange is modulated by turbulent mixing through its effect on density stratification. Here we quantify turbulent mixing in Hikapu Reach, an estuarine channel in the Marlborough Sounds, New Zealand. The focus is on a period of relatively low freshwater input but where density stratification still persists throughout the tidal cycle, although the strength of stratification and its vertical structure vary substantially. The density stratification increases through the ebb tide, and decreases through the flood tide. During the spring tides observed here, ebb tidal flow speeds reached 0.7?m?s^?1 and the buoyancy frequency squared was in the range 10^?5 to 10^?3?s^?2. Turbulence parameters were estimated using both shear microstructure and velocimeter-derived inertial dissipation which compared favourably. The rate of dissipation of turbulent kinetic energy reached 1?×?10^?6?m²?s^?3 late in the ebb tide, and estimates of the gradient Richardson number (the ratio of stability to shear) fell as low as 0.1 (i.e. unstable) although the results show that bottom-boundary driven turbulence can dominate for periods. The implication, based on scaling, is that the mixing within the channel does not homogenise the water column within a tidal cycle. Scaling, developed to characterise the tidal advection relative to the channel length, shows how riverine-driven buoyancy fluxes can pass through the tidal channel section and the stratification can remain partially intact.  相似文献   

THE CHEMICAL COMPOSITION AND CLASSIFICATION OF THE KAROONDA METEORITE     

M.J. Fitzgerald 《Meteoritics & planetary science》1979,14(1):109-115

New bulk compositional results are presented for the Karoonda meteorite which show that it is a member of the Vigarano type carbonaceous chondrites. Use of the petrographic symbol CK for Karoonda is shown to be unnecessary and inadvisable.  相似文献   

Automatic subpixel registration for a tunable hyperspectral imaging system   总被引：3，自引：0，他引：3  

Erives  H. Fitzgerald  G.J. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(3):397-400

Hyperspectral imagery of the Earth's surface is increasingly being acquired from aerial platforms. The many bands acquired by typical hyperspectral instruments are collected either in a push-broom, scanning, or staring fashion. Staring methods can be used in ground- and aerial-based applications and have the advantage of readily producing coherent images. Staring remote sensing instruments need some form of coregistration to match band-to-band pixel locations because it takes some time for the instrument to acquire images and save them as the aerial platform moves above the target scene. A well-known method for registration is the phase correlation (PC), which may be used to register images to an accuracy of /spl plusmn/1 pixels. This letter reports an enhancement to the PC method that allows for subpixel registration of hyperspectral images. The x-y location at which the maximum correlation function occurs is fitted with a cubic interpolation to find the maximum. This method was implemented to recover subpixel rotation and translation accuracy from an airborne hyperspectral imaging system, dubbed the Portable Hyperspectral Tunable Imaging System. Results showed that the approach improves up to 9.5% of the normalized cross correlation between wavebands in comparison with the PC method alone.  相似文献   

Acceptance of the 2003 Clair C. Patterson Award     

William F Fitzgerald 《Geochimica et cosmochimica acta》2004,68(9):1961-1962

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Seasonal variations of the clear-sky greenhouse effect: the role of changes in atmospheric temperatures and humidities     

MJ Webb  A Slingol  GL Stephens 《Climate Dynamics》1993,9(3):117-129

We present an analysis of the factors which control the seasonal variations of the clear-sky greenhouse effect, based on satellite observations and radiative transfer simulations. The satellite observations include the radiation budget at the top of the atmosphere from the Earth Radiation Budget Experiment and the total column moisture content derived from the Special Sensor Microwave/Imager. The simulations were performed with the SAMSON system described in an earlier paper, using atmospheric temperatures and humidities from operational analyses produced by the European Centre for Medium Range Weather Forecasts. At low latitudes, the magnitude of the clear-sky greenhouse effect is dominated by the strong thermodynamic link between the total column moisture content of the atmosphere and sea surface temperatures, with minimal seasonal variations. In contrast, at middle to high latitudes there are strong seasonal variations, the clear-sky greenhouse effect being largest in winter and smallest in summer. These variations cannot be explained by the seasonal cycle in the total column moisture content, as this is largest in summer and smallest in winter. The variations are controlled instead by the seasonal changes in atmospheric temperatures. The colder atmosphere in winter enhances the temperature differential between the atmosphere and the sea surface, leading to a larger greenhouse effect despite the lower moisture contents. The magnitude of the clear-sky greenhouse effect is thus controlled by atmospheric humidity at low latitudes, but by atmospheric temperature at middle and high latitudes. These controls are illustrated by results from sensitivity experiments with SAMSON and are interpreted in terms of a simple model.  相似文献   

Statistical aspects of Tricomi's function and modified Bessel functions of the second kind     

D. L. Fitzgerald 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(2):139-158

Some of the considerable statistical content of modified Bessel functions of the second kind and of Tricomi's confluent hypergeometric function is illustrated. Moment solutions for the parameters of exponential class distribution functions based on both are derived. Unlike the generalised inverse Gaussian, the Tricomi exponential distribution is little known but it emerges that it is of wide applicability, highly flexible and has the gamma distribution as a special case.  相似文献