Review of coking phenomena in relation to an occurrence of prismatically fractured natural coke from the Castle Mountain mine, Matanuska coal field, Alaska     

Roy D. Merritt 《International Journal of Coal Geology》1985,4(4):281-298

Brief consideration is given to the formation and characteristics of natural coke and its similarities to industrial coke. Observations relating to an occurrence of prismatically fractured natural coke at the Castle Mountain coal mine of the central Matanuska Valley, Alaska are discussed. The temperature gradient across the naturally coked seam here is estimated to have ranged from 350°C at the top to 550°C at the bottom of the seam directly adjacent to the sill. The importance of studying coal-intrusive relationships and natural coking phenomena stems from the effects that intruding dikes and sills have on coal continuity, quality, and potential minability.  相似文献   

Wind energy estimates by use of a diagnostic model     

Roy M. Endlich 《Boundary-Layer Meteorology》1984,30(1-4):375-386

A diagnostic model is a relatively simple and practical tool for modeling the wind flow of the boundary layer in complex terrain. The model begins with a wind analysis based on available surface wind reports and geostrophic winds (computed from pressure data). The height of the boundary layer top (upper surface of the computational domain) is prescribed to fit local conditions. Using the continuity equation in terrain-following coordinates, the winds at mesh points are adjusted to produce nondivergence while maintaining the original vertical component of vorticity. The method of computing the nondivergent winds uses direct alterations. This method may be useful for other modeling purposes and will be described. Data for a long period (usually a year) are analyzed to obtain eigenvectors and the associated time series of their coefficients at each observation time. The model is run only for the five or six eigenvectors that explain most of the variance. The wind field at any particular time is reconstructed from the eigenvector solutions and their appropriate coefficients. Comparisons of model results with measured winds at sites representing different types of terrain will be shown. The accuracy and economy of the model make it a useful tool for estimating wind energy and also for giving wind fields for low-level diffusion models.  相似文献   

Uranium geochemistry in groundwater from tertiary sediments     

Roy F. Spalding  A.Douglas Druliner  Lowell S. Whiteside  Arthur W. Struempler 《Geochimica et cosmochimica acta》1984,48(12):2679-2692

Dissolved U concentrations and activity ratios (ARs) of the U isotopes in the ²³⁸U decay series were measured in ground and surface waters as part of an investigation to delineate the water quality in a proposed uranium mining area of northwest Nebraska. In oxidizing groundwaters from 67 wells completed in the Tertiary sediments, increasing U concentrations in the direction of groundwater flow generally were associated with a maturation of the formation water as evidenced by evolutionary trends in major ion character. The increased U levels probably are associated with leaching as shown by the positive correlation between U concentrations and total dissolved solids (TDS) (r = +0.83). The inverse relationships between TDS and U ARs (r = ?0.73) and U levels and ARs (r = 0.72) indicate that the decay of excess U-234 is related to maturation of the formation water and to sediment leaching along the flowpath. The data are described by a model which incorporates etching, decay and recoil and suggests that aquifer residence time can be estimated from the TDS level.The levels of soluble U in a reducing uraniferous hydrogeologic unit near Crawford, Nebraska are affected by the proximity of the sample collection to ore. In groundwater samples having similar chemistries (Na-SO₄ + Cl type), similar Ehs, and collected from a close-knit pattern, U concentrations ranged from 0.01 to 2,037 μg l^?1 and ARs ranged from 0.75 to 12.6. This high variability in U levels and ARs is indicative of uranium ore in small areal studies where low ARs almost always are associated with high U concentrations.  相似文献   

Genetic reinterpretation of crystallographicintergrowths of jacobsite andhausmannite from natural assemblages     

Dr. Somnath Dasgupta  P. K. Bhattacharya  G. Chattopadhyay  M. Fukuoka  H. Banerjee  Supriya Roy 《Mineralogy and Petrology》1987,37(2):109-116

Summary Crystallographic intergrowths of jacobsite and hausmannite (vredenburgite) occur in association with braunite in the Precambrian Sausar Group of rocks, India, that were metamorphosed under 600-700°C and P 6 kb. Quartz, hematite, rhodochrosite and a later hausmannite may occasionally occur as minor associates. Detailed characterization of the intergrown phases reveals that hausmannite lamellae, oriented in 4 or 5 crystallographic directions in the jacobsite host, show a wide variation in thickness and tapered intersections at low angles. The lamellae may be locally deformed. Analytical data reveal that the composition of natural hausmannite and jacobsite in the intergrowths cannot be approximated within the system Fe₃O₄ -Mn₃O₄, as has been conventionally done. These really belong to the Fe₂O₃-Mn₃O₄ subsystem. In the two phase intergrowths, hausmannite is depleted and the jacobsite is enriched in Fe in higher grade rocks. Mineral associations and petrographic considerations suggest that the jacobsite-hausmannite intergrowth originated through prograde decarbonation-oxidation reactions of a carbonatic precursor in an unbuffered X CO₂ situation, but f O₂ was held between hematite-magnetite and bixbyite-hausmannite buffers at the ambient physical conditions of metamorphism. Subsequent oxidation yielded a strong oxygenbuffering assemblage jacobsite, hausmannite, braunite, hematite and quartz. This study negates the commonly held idea that hausmannite jacobsite crystallographic intergrowth (vredenburgite) originates through unmixing of a high ([ldvredenburgite) originates through unmixing of a high temperature spinel_ss temperature spinel_ss during cooling.

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Genetische Reinterpretation der kristallographischen Verwachsungen von Jakobsit und Hausmannit in natürlichen Vorkommen

Zusammenfassung Kristallographische Verwachsungen von Jakobsit und Hausmannit (Vredenburgit) treten in Verbindung mit Braunit in Gesteinen der präkambrischen Sausargruppe in Indien auf. Die Gesteine wurden bei Drucken von ca. 6 kbar und Termperaturen von 600–700°C metamorphosiert. Quarz, Hämatit, Rhodochrosit, und Hausmannit als Spätphase treten gelegentlich als untergeordnete Gemengteile auf. Hausmannit-Lamellen, die in vier oder fünf kristallographischen Richtungen in Jakobsit orientiert sind, haben sehr unterschiedliche Durchmesser und bilden versetzte Zwickel in kleinem Winkel mit dem Jakobsit. Die Lamellen können lokal deformiert sein. Analytische Daten zeigen, daß die Zusammensetzung von natürlichem Hausmannit und Jakobsit in Verwachsungen nicht, wie bisher angenommen, in dem System Fe₃O₄-Mn₃O₄ dargestellt werden kann. Diese Verwachsungen gehören vielmehr in das Fe₂O₃-Mn₃O₄ System. In höher-gradigen metamorphen Gesteinen ist Fe in zwei-phasigen Verwachsungen im Hausmannit ab- und im Jakobsit angereichert. Die Mineralzusammensetzung und petrographische Gesichtspunkte lassen darauf schließen, daß die Jakobsit/Hausmannit Verwachsung durch prograde Dekarbonatisierung/Oxydationsreaktion eines karbonatischen Vorläufers in einem nicht gepufferten X CO₂ Milieu entstanden ist. F O₂ wurde durch Hämatit-Magnetit und Bixbyit-Hausmannit Puffer unter den gegebenen physikalischen Bedingungen der Metamorphose stabil gehalten. Eine nachfolgende Oxydation führte zu einer starken Sauerstoff-puffernden Assoziation von Jakobsit, Hausmannit, Braunit, Hämatit und Quarz. Diese Untersuchungen widerlegen die allgemein verbreitete Ansicht, daß die kristallographische Verwachsung von Hausmannit und Jakobsit (Vredenburgit) durch Entmischung eines Hochtemperatur-Spinells während der Abkühlung entstanden ist.

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With 1 figure  相似文献   

Representativeness of total ozone trends as derived from satellite BUV and ground-based measurements     

Christos S. Zerefos  Christos C. Repapis  Roy L. Jenne 《Pure and Applied Geophysics》1982,120(1):29-53

The information content of the 7-year BUV data set has been reexamined by a comparison with a fairly large set of ground Dobson and M-83 instruments. The satellite-ground intercomparison of total ozone was done under different types of ground observation techniques (observation code) and different instrument exposure (exposure code) and for various distances of the subsatellite point from the station. Because of the existing latitudinal gradient in total ozone, at a given station the bias ground-BUV tends to be smaller when the subsatellite point is at a latitude higher than the station's latitude. Knowing the total ozone gradient at a given station, the BUV total ozone has been corrected to account for the ozone gradient and the correlation was calculated with the corresponding ground observations. These correlations seem to offer no improvement when compared with the correlations between the ground ozone and the actual BUV ozone at distances of the subsatellite point from the station within 200 km from the station used in previous studies. The seasonal variation of the BUV-ground correlation reveals information on the noise level of the measurements and the geographical distribution of the percentage mean bias: (Ground-BUV)×100/(Ground) is discussed. Both on short and on longer time scales it appears that the BUV derived recommended total ozone data set is reasonably good and possible instrumental drifts are not large. The analysis includes an extension through April 1977 of the BUV and contour-derived total ozone trends byLondon andLing (1980). Over the northern hemisphere both data sets (contour and BUV) show comparable trends over middle and high latitudes which range from –3 D.U./year to –5 D.U./year during the 7-year period April 1970–April 1977. In the southern hemisphere, however, long-term variation in total ozone cannot be determined from ground observations alone. It is concluded that for unknown reasons during the 7-year period of study, total ozone has been decreasing over most of the globe. The negative growth rates at high latitudes of the northern hemisphere are highly significant.  相似文献   

Paleomagnetic results from Mio-Pliocene marine sedimentary series in Crete     

J.-P. Valente  C. Laj  D. Sorel  S. Roy  J.-P. Valet 《Earth and Planetary Science Letters》1982,57(1):159-172

Paleomagnetic measurements have been conducted on Mio-Pliocene marine sedimentary series from Crete in order to detect any eventual rotation of this island. The results obtained from 14 stable sites of Tortonian age (～ 7 m.y.) yield a paleomagnetic pole not significantly different from either the European or the African ones, showing that Crete has not undergone any significant rotation since that epoch.  相似文献   

The structure of two South Carolina estuarine tide pool fish assemblages     

Roy E. Crabtree  John Mark Dean 《Estuaries and Coasts》1982,5(1):2-9

The fish assemblages of two South Carolina estuarine tide pools located in the North Edisto River were sampled from June to October 1977, and during June and July 1978, by haul seine, lift net and channel net. The nekton was dominated numerically byFundulus heteroclitus, Leiostomus xanthurus, Menidia menidia andAnchoa mitchilli. Oyster reef areas were dominated numerically byGobiosoma bosci andF. heteroclitus. The relative abundance of tide pool fishes differs from deep water areas of the North Edisto River as described from otter trawls, but is similar to that described by others for South Carolina tidal creeks.  相似文献   

Sorption of noble gases by solids,with reference to meteorites. I. Magnetite and carbon     

Jongmann Yang  Roy S. Lewis  Edward Anders 《Geochimica et cosmochimica acta》1982,46(6):841-860

To simulate trapping of meteoritic noble gases by solids, 18 samples of Fe₃O₄ were synthesized in a noble gas atmosphere at 350–720 K by the reactions: 3Fe + 4H₂O → Fe₃O₄ + 4H₂ (Ne, Ar, Kr, Xe) 3Fe + 4CO → Fe₃O₃ + 4C + carbides (Xe only) Phases were separated by selective solvents (HgCl₂, HCl). Noble gas contents were analyzed by mass spectrometry, or, in runs where 36 d Xe¹²⁷ tracer was used, by γ-counting. Surface areas, as measured by the BET method, ranged from 1 to 400 m²/g. Isotopic fractionations were below the detection limit of 0.5%/m.u.Sorption of Xe on Fe₃O₄ and C obeys Henry's Law between $\text{1 × 10}{}^{\mathrm{?8}}$ and $\text{4 × 10}{}^{\mathrm{?5}}$ atm, but shows only a slight temperature dependence between 650 and 720 K ($\text{ΔH}{}_{\mathrm{sol}}\text{= ?4 ± 2}\text{kcal/mole}$). The mean distribution coefficient K_Xe is $\text{0.28 ± 0.09}$ cc STP/g atm for Fe₃O₄ and only a factor of $\text{1.2 ± 0.4}$ greater for C; such similarity for two cogenetic phases was predicted by Lewis et al. (1977). Stepped heating and etching experiments show that 20–50% of the total Xe is physically adsorbed and about 20% is trapped in the solid. The rest is chemisorbed with $\text{ΔH}{}_{\mathrm{s}}\text{? ?13}\text{kcal/mole}$. The desorption or exchange half-time for the last two components is >10² yr at room temperature.Etching experiments showed a possible analogy to “Phase $\text{Q}$” in meteorites. A typical carbon + carbide sample, when etched with HNO₃, lost 47% of its Xe but only 0.9% of its mass, corresponding to a ~0.6 Å layer. Though this etchable, surficial gas component was more thermolabile than $\text{Q}$ (release $\text{T}$ below 1000°C, compared to 1200–1600°C), another experiment shows that the proportion of chemisorbed Xe increases upon moderate heating (1 hr at 450°C). Apparently adsorbed gases can become “fixed” to the crystal, by processes not involving volume diffusion (recrystallization, chemical reaction, migration to traps, etc.). Such mechanisms may have acted in the solar nebula, to strengthen the binding of adsorbed gases.Adsorbed atmospheric noble gases are present in all samples, and dominate whenever the noble gas partial pressure in the atmosphere is greater than that in the synthesis. Many of the results of Lancet and Anders (1973) seem to have been dominated by such an atmospheric component; others are suspect for other reasons, whereas still others seem reliable. When the doubtful samples of Lancet and Anders are eliminated or corrected, the fractionation pattern—as in our samples—no longer peaks at Ar, but rises monotonically from Ne to Xe. No clear evidence remains for the strong temperature dependence claimed by these authors.  相似文献   

Polycyclic aromatic hydrocarbon (PAH)-phase associations in Washington coastal sediment     

Fredrick G Prahl  Roy Carpenter 《Geochimica et cosmochimica acta》1983,47(6):1013-1023

Polycyclic aromatic (PAH) and aliphatic hydrocarbon compositions, organic carbon, nitrogen and lignin contents were determined in whole, unfractionated sediment from the Washington continental shelf and in discrete sediment fractions separated by particle size and density. At least 20 to 25% of perylene and PAH derived from pyrolytic processes and 50% of the retene measured in whole sediment are contained within organic C- and lignin-rich panicles of density ≤ 1.9 g/cc. These particles, which include primarily vascular plant remains and bits of charcoal, comprise less than 1% of the total sediment weight. In contrast, a series of methylated phenanthrene homologs, possibly of fossil origin, are concentrated in some component of the more dense, lithic matrix of the sediment. Equilibrium models of PAH sorption/desorption from aqueous phase onto small particles of high surface area do not appear applicable to the behavior of the major PAH types identified in this aquatic environment.  相似文献   

Understanding confluence dynamics in the alluvial Ganga–Ramganga valley, India: An integrated approach using geomorphology and hydrology     

Nanigopal Roy  Rajiv Sinha   《Geomorphology》2007,92(3-4):182

Confluence dynamics in the Ganga–Ramganga valley in the western Ganga plains of India has been studied through systematic mapping of channel configuration using multi-date remote sensing images and topographic sheets for a period spanning nearly 100 years (1911–2000). The study has been supplemented with a detailed analysis of the channel morphology, hydrology and sediment transport characteristics of the different rivers. Our study indicates that new confluences have been created during this period and that the confluence points have moved both upstream and downstream on a historical time scale. Apart from major avulsions, other processes that have controlled the confluence movements include river capture, cut-offs and aggradation in the confluence area. River capture occurs through lateral bank erosion and migration, encroachment by the master stream and beheading of smaller rivers resulting in upstream movement of the confluence point. Another process which influences the upstream migration of the confluence is an increase in sinuosity of one of the channels near the confluence and then a cut-off. Aggradation in the confluence area and local avulsions of the primary channel in a multi-channel system seem to be the major process controlling the downstream movement of the confluence point. Analysis of channel morphology, hydrology and sediment budget for the study period supports our interpretations.  相似文献