Josephinite: specimens from the earth's core? — a discussion     

Henry J.B. Dick  Holmes Gillete 《Earth and Planetary Science Letters》1976,31(2):308-311

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$\text{U}{}^{234}\text{U}{}^{238}$ Ratios in limestone cave seepage waters and speleothem from West Virginia     

Peter Thompson  Derek C Ford  Henry P Schwarcz 《Geochimica et cosmochimica acta》1975,39(5):661-669

Speleothem from West Virginia, ranging in age from 2000 to 200,000 yr B.P. contains uranium with $\text{U}{}^{234}\text{U}{}^{238}$ ratios significantly greater than unity. This ratio varies from one speleothem to another, as does average U content. Initial ratios, corrected for age, are remarkably constant for a given speleothem. By contrast, $\text{U}{}^{234}\text{U}{}^{238}$ ratios in seepage waters vary significantly from month to month at a given drip site, and their average values differ from that of the speleothem which they are depositing. This discrepancy is attributed either to long-term averaging-out of fluctuations, or fractional precipitation on the speleothem of a chemical species of uranium with a more constant ratio. Constancy of initial $\text{U}{}^{234}\text{U}{}^{238}$ ratios from $\text{Th}{}^{230}\text{U}{}^{234}$. datable portions of speleothems should permit $\text{U}{}^{234}\text{U}{}^{238}$-dating of older portions of the same speleothem, back to about 10⁶ yr B.P., with estimated precision of ±5 per cent.  相似文献   

The growth response of an estuarine diatom (Melosira nummuloides [dillw.] Ag.) to UV-B (290–320 nm) radiation     

Bruce E. Thomson  Robert C. Worrest  Henry Van Dyke 《Estuaries and Coasts》1980,3(1):69-72

An increase in the transmission of solar radiation in the UV-B region (specifically, 290–320 nm) is expected to occur as a result of anthropogenic degradation of stratospheric ozone. The potential impact of increased levels of UV-B radiation upon the biosphere is of ecological concern. In a previous study a community of estuarine organisms received a daily exposure to a simulated solar spectrum enhanced in UV-B radiation for a period of six weeks. A dominant species of diatom growing at the surface of these communities was isolated and identified to beMelosira nummuloides. Short chains of this diatom were irradiated for a four-hour period on each of three consecutive days. Fluorescent sunlamps filtered by a 290 nm cut-off filter (0.13–0.50 mm cellulose acetate) or a 315 nm cut-off filter (0.13mm Mylar ‘S’) provided a range of fluence which closely approximated natural fluence levels. A least squares regression analysis of the number of cell divisions on the biologically weighted fluence indicated a significant depression in the growth of this species by radiation in the 290–320 nm waveband.  相似文献   

The redox state of cerium in basaltic magmas: an experimental study of iron-cerium interactions in silicate melts     

Henry D. Schreiber  Howard V. Lauer  Thitinant Thanyasiri 《Geochimica et cosmochimica acta》1980,44(10):1599-1612

Ce(IV)-Ce(III) and Fe(III)-Fe(II) redox equilibria in Ca-Mg-Al-silicate melts have been individually measured with respect to the base composition, melt temperature, imposed oxygen fugacity, and multivalent element concentration (up to about 1.5 wt%). The mutual interaction of these two redox couples has been studied in analogous glasses which simultaneously contained iron and cerium. Analyses of Fe(III) concentrations in iron-cerium glasses by electron paramagnetic resonance and optical absorption spectroscopy indicate that Ce(IV) is stoichiometrically reduced by Fe(II) in the melt to produce Fe(III) and Ce(III) and that Ce(III)-O-Fe(III) complexes are formed in the melt. Consequently, it is concluded that cerium exists only as Ce(III) in basaltic magmas; cerium anomalies cannot be ascribed to the stabilization of Ce(IV) in magmas.  相似文献   

Terrestrial nickel-iron from the Josephine Peridotite,its geologic occurrence,associations, and origin     

Henry J.B. Dick 《Earth and Planetary Science Letters》1974,24(2):291-298

The distribution of placers containing coarse nuggets of the nickel-iron alloy, josephinite, are found to have a close spatial relationship to a narrow zone of intense shearing, serpentinization, and igneous intrusion within the Josephine Peridotite. These field relations, together with the frequent occurrence of magnetite and serpentine with the alloy, indicate that the mineral is the product of hydrothermal metamorphism and serpentinization of the peridotite. This is confirmed by the discovery of the nickel-iron in serpentine veins cutting moderately altered harzburgite. Andradite garnet, a common skarn mineral produced by contact metamorphism around igneous intrusions, is often intergrown with the nickel-iron. This may indicate that the unusually coarse grain size of the josephinite is the result of the special conditions accompanying igneous intrusion in the serpentine belt.  相似文献   

On the chemical composition of atmospheric aerosols — Part I: Some stoichiometric aspects of the problem     

Henry M. Papée 《Pure and Applied Geophysics》1959,44(1):191-203

Summary Following a recent hypothesis on the role of activated sodium chloride particles as possible condensation and sublimation nuclei, an analysis of data given byC. Junge on the chemical composition of aerosols, is made. It is established that all reported giant nuclei fall into three distinct categories of composition and that within each of these categories the ratio of the sums of anions to the sums of cations for constituents for which analyses were made, remains remarkably constant throughout the days of sampling, and for both geographic positions at which sampling has been carried out. A dependence of the hydroxide-carbonate content, on that of nitrate is also indicated in the «alkaline» nuclei. The system is treated as a saturated solution, and it is shown by the procedure of continuous variations that singularities occur at particular ratios of the prevalent chemical groups in solution, possibly indicating formation of complex species. This, together with the presence of double salts in the solid phase may be partly the reason for the constancy of ratio of sums in the groups of particles studied byJunge, while the grouping itself may depend on the origin and subsequent transformations of the particles.Parts of this paper were presented at the 174-th National Meeting of the American Meteorological Society, on the 29-th of January, 1959, in New York.  相似文献   

Exploration Techniques at the Thorn Ag-Au-Cu High-Sulfidation Epithermal Prospect, Northern British Columbia, Canada     

Henry Awmack 《Resource Geology》2002,52(4):283-290

Abstract. The Thorn prospect is an El Indio-style high-sulfidation epithermal prospect in a little-explored belt of Late Cretaceous subaerial volcanics and subvolcanic intrusions in northwestern British Columbia, Canada. More than 30 massive sulfide (pyrite-enargite-tennantite/tetrahedrite) veins, quartz-sulfide (quartz-pyrite-enargite-tennantite/tetrahedrite) veins and quartz-vuggy silica-alunite veins/breccias fill ENE fractures and faults over an area of 1,600 times 1,900 m. They are hosted within a Late Cretaceous feldspar-quartz-biotite granodioritic porphyry stock and flanked by alteration envelopes a few meters to tens of meters wide: an inner envelope of intense sericite-clay-pyrite and an outer one of weak clay-sericite-chlorite. Where several veins are close together, the sericite-clay-pyrite alteration envelopes coalesce into zones up to 150 m wide.
The most successful exploration techniques have been prospecting, silt and soil geochemistry, airborne magnetic and electromagnetic surveys and diamond drilling. Silt and soil geochemical anomalies for Au, Ag, As, Cu, Pb, Sb and Zn mark the known veins and indicate prospective areas where veins have not yet been discovered. Magnetics and resistivity outline the gross property-wide structure and lithologies. Most of the sericite-clay-pyrite alteration and known veins are outlined by the <264 ohm-m resistivity contour, which covers an area of 800 times 2,300 m. Weak EM conductors are thought to represent undiscovered massive sulfide and quartz-sulfide veins, and their flanking sericite-clay-pyrite alteration.  相似文献   

THE USE OF AERIAL PHOTOGRAPHIC ARCHIVES BY CONSULTING ENGINEERS     

C. J. Henry 《The Photogrammetric Record》1989,13(73):139-151

Post-war survey photography provides a detailed record of the great changes which have occurred in this period. Pictures of urban expansion, land reclamation, quarrying and infilling and industrial decline can be seen in three dimensions and be measured and analysed. The record of change is of great practical significance to engineers.  相似文献   

Induced Stresses and Fault Potential In Eastern Canada Due to A Disc Load: A Preliminary Analysis   总被引：1，自引：0，他引：1  

Patrick Wu  Henry S. Hasegawa 《Geophysical Journal International》1996,125(2):415-430

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Disaster vulnerability: Scale,power and daily life   总被引：13，自引：0，他引：13  

Ben Wisner  Henry R. Luce 《GeoJournal》1993,30(2):127-140

The author gratefully acknowledges the stimulation over a number of years of his co-authors in a project about to appear in 1994 under the title,At Risk: Natural Hazards, People's Vulnerability and Disasters, Routledge, London & New York — Piers Blaikie, Terry Cannon, and Ian Davis.Earlier versions of this paper were discussed by session on disasters organized by Tony Oliver-Smith at the annual meeting of the Society for Applied Anthropology, Memphis, March, 1992 and at the Famine and Food Systems Study Group of the International Geographical Union, convened at Tufts University, July, 1992, by John Field and Hans Bohle. My thanks as well to colleagues who participated in these two discussions.  相似文献