Radiochemical Determination of Gold in Rocks     

Evgeny TASKAEV  Ivan PENEV  Hubert SCHELHORN  Martin GEISLER 《Geostandards and Geoanalytical Research》1987,11(1):103-106

A method developed for radiochemical determination of gold in rock samples has been applied to six Bulgarian, four ZGI (GDR) and one USGS geostandards. The method is based on acid dissolution of the sample, followed by extraction of gold with copper diethyldithiocarbamate solution in CHCl₃. The chemical yield was determined by using ¹⁹⁹Au tracer. The present data are compared with published values for the ZGI and USGS samples.  相似文献   

Kinematics of refracted and reflected waves in inhomogeneous media with non-planar interfaces     

Ivan Pšenčík  Reviewer V. Červený 《Studia Geophysica et Geodaetica》1972,16(2):126-152

Zusammenfassung Es werden die Grundbeziehungen für die Berechnung von Strahlen seismischer Wellen in inhomogenen Milieus abgeleitet, in denen die Geschwindigkeit allgemein von drei krummlinigen Koordinaten abhängt. Die angeführten Beziehungen stellen ein System von gewöhnlichen Differentialgleichungen erster Ordnung dar. Die numerische Lösung dieses Systems bietet eine Möglichkeit, die Strahlendiagramme, Laufzeitkurven und Isochronen für die gegebenen Geschwindigkeitsmodelle zu konstruieren. Aufmerksamkeit wird ebenfalls dem Einfall der Strahlen auf eine unebene Grenzschicht gewidmet. Die Beziehungen für die Berechnung reflektierter und refraktierter Strahlen werden abgeleitet. Anhand der abgeleiteten Beziehungen werden Strahlendiagramme und Laufzeitkurven für eine Geschwindigkeitsverteilung berechnet, die durch die vorläufige Interpretation der Ergebnisse von seismischen Tiefensondierungen am tschechoslowakischen Teil des Profils VI gewonnen wurden.  相似文献   

Metamorphic assemblages and the direction of flow of metamorphic fluids in four instances of serpentinization   总被引：3，自引：0，他引：3  

Ivan Barnes  John B. Rapp  James R. O'Neil  Richard A. Sheppard  Arthur J. Gude III 《Contributions to Mineralogy and Petrology》1972,35(3):263-276

Fluids related to Serpentinization are of at least three types. The first reported (Barnes and O'Neil, 1969) is a fluid of local meteoric origin, the chemical and thermodynamic properties of which are entirely controlled by olivine, orthopyroxene, brucite, and serpentine reactions. It is a Ca⁺²-OH^–1 type and is shown experimentally to be capable of reacting with albite to yield calcium hydroxy silicates. Rodingites may form where the Ca⁺²-OH^–1 type waters flow across the ultramafic contact and react with siliceous country rock.The second type of fluid has its chemical composition largely controlled before it enters the ultramafic rocks, but reactions within the ultramafic rocks fix the thermodynamic properties by reactions of orthopyroxene, olivine, calcite, brucite, and serpentine. The precipitation of brucite from this fluid clearly shows that fluid flow allows reaction products to be deposited at a distance from the point of solution. Thus, textural evidence for volume relations during Serpentinization may not be valid.The third type of fluid has its chemical properties fixed in part before the reactions with ultramafic rocks, in part by the reactions of orthopyroxene, olivine, and serpentine and in part by reactions with siliceous country rock at the contact. The reactions of the ultramafic rock and country rock with the fluid must be contemporaneous and require flow to be along the contact. This third type of fluid is grossly supersaturated with talc and tremolite, both found along the contact. The occurrence of magadiite, kenyaite, mountainite, and rhodesite along the contact is probably due to a late stage low-temperature reaction of fluids of the same thermodynamic properties as those that formed the talc and tremolite at higher temperatures. Oxygen isotope analyses of some of these minerals supports this conclusion.Rodingites form from Ca⁺²-rich fluids flowing across the contact; talc and tremolite form from silica-rich fluids flowing along the contact.Isotopic analyses of the fluids indicate varied origins including unaltered local meteoric water and connate water. Complexion Spring water may be a sample of only slightly altered Jurassic or Cretaceous sea water.Publication authorized by the Director, U.S. Geological Survey.  相似文献   

Mortar Upscaling for Multiphase Flow in Porous Media   总被引：1，自引：0，他引：1  

Małgorzata Peszyńska  Mary F. Wheeler  Ivan Yotov 《Computational Geosciences》2002,6(1):73-100

In mortar space upscaling methods, a reservoir is decomposed into a series of subdomains (blocks) in which independently constructed numerical grids and possibly different physical models and discretization techniques can be employed in each block. Physically meaningful matching conditions are imposed on block interfaces in a numerically stable and accurate way using mortar finite element spaces. Coarse mortar grids and fine subdomain grids provide two-scale approximations. In the resulting effective solution flow is computed in subdomains on the fine scale while fluxes are matched on the coarse scale. In addition the flexibility to vary adaptively the number of interface degrees of freedom leads to more accurate multiscale approximations. This methodology has been implemented in the Center for Subsurface Modeling's multiphysics multiblock simulator IPARS (Integrated Parallel Accurate reservoir Simulator). Computational experiments demonstrate that this approach is scalable in parallel and it can be applied to non-matching grids across the interface, multinumerics and multiphysics models, and mortar adaptivity. Moreover unlike most upscaling approaches the underlying systems can be treated fully implicitly.  相似文献   

Water quality model of the Danube in its Bulgarian part     

Ivan Diadovski  Veska Kazantzeva 《Aquatic Sciences - Research Across Boundaries》1996,58(3):269-279

Models for predicting river water quality could assist protection and utilization of water resources under alternative management strategies. The model of the water quality characteristics of the Danube is based on an ecosystem approach. Considered are all waste water discharges and inflow of tributaries among the catchment area. The identification of model parameters is realized according to the method of integral transformation. For the performance of the model a computer program was elaborated. It is applied in predicting the water quality of the Danube considering almost 20 indicators for the abiotic and biotic parameters of river ecosystem.  相似文献   

Some properties of unstable slip on rough surfaces     

Hartmut Spetzler  Guennadi Sobolev  Anatoli Koltsov  Arno Zang  Ivan C. Getting 《Pure and Applied Geophysics》1991,137(1-2):95-112

In this paper we report results obtained from various friction experiments under direct and oblique shear loading conditions. We used four rock types of varying brittleness (quartzite, anhydrite, limestone, pyrophyllite) with different surface roughness. The observations concentrate on the time span several milliseconds before dynamic failure occurs. During this period a premonitory, unstable phase of slip (slip 2) occurs. This differs importantly from a premonitory, stable process (slip 1) with durations of hundreds of seconds. On smooth surfaces slip 2 is usually observed with ductile rocks and less reliably with brittle rocks. Slip 2 is mostly accompanied by acoustic emissions, which increase in rate of occurrence and in magnitude until the stick-slip event. Foreshocks are observed during approximately 50% of the slip 2 events on rough surfaces. Foreshocks far exceed the acoustic noise level, which is also prevalent before stick-slip events on rough surfaces. In the direct shear experiment, where two faults are being loaded simultaneously, in about 20% of the cases precursory slip 2 was observed on the opposite side on which the final stick-slip event occurred.  相似文献   

Computation of additional components of the first-order ray approximation in isotropic media     

Leo Eisner  Ivan Pšenčík 《Pure and Applied Geophysics》1996,148(1-2):227-253

This study shows that the use of the first-order additional components of the ray method in the seismic wave field modeling is easy and that it can bring a substantial improvement of the standard ray results obtained with the zero-order ray approximation only. For the calculation of a first-order additional component, spatial derivatives of the parameters of the medium and spatial derivatives of the zero-order ray amplitude term are necessary. The evaluation of the former derivatives is straightforward; the latter derivatives can be calculated approximately from neighboring rays by substituting the derivatives by finite differences. This allows an effective calculation of the first-order additional terms in arbitrary laterally varying layered media.The importance of the first-order additional terms is demonstrated by the study of individual higher-order terms of the ray series representing elementaryP andS elastodynamic Green functions for a homogeneous isotropic medium. The study shows clearly that the consideration of the first-order additional terms leads to a more substantial decrease of the difference between approximate and exact elementary Green functions than any other higher-order term. With this in mind, effects of the first-order additional terms on the ray synthetic seismograms for aVSP configuration are studied. It is shown that the use of the additional terms leads to such phenomena, unknown in the zero-order approximation of the ray method, like quasi-elliptical and transverse polarization of a singleP wave or longitudinal polarization of a singleS wave.  相似文献   

Hyperboloidal precession of a dynamically symmetric satellite. Construction of normal forms of the Hamiltonian     

Ivan I. Shevchenko  Andrej G. Sokolsky 《Celestial Mechanics and Dynamical Astronomy》1995,62(4):289-304

The Norma specialized program package, intended for normalization of autonomous Hamiltonian systems by means of computer algebra, is used in studies of small-amplitude periodic motions in the neighbourhood of regular precessions of a dynamically symmetric satellite on a circular orbit. The case of hyperboloidal precession is considered. Analytical expressions for normal forms and generating functions depending on frequencies of the system as on parameters are derived. Possible resonances are considered in particular. The 6th order of normalization is achieved. Though the intermediate analytical expressions occupy megabytes of computer's main memory, final ones are quite compact. Obtained analytical expressions are applied to the analysis of stability of small-amplitude periodic motions in the neighbourhood of hyperboloidal precession.  相似文献   

Fecundity and spawning of the Atlantic horseshoe crab, Limulus polyphemus, in Pleasant Bay, Cape Cod, Massachusetts, USA     

Alison S. Leschen  Sara P. Grady  & Ivan Valiela 《Marine Ecology》2006,27(1):54-65

This study provided the first comprehensive analysis of Atlantic horseshoe crab (Limulus polyphemus) fecundity. Limulus appear to be a determinate spawner, maturing all eggs for the breeding season before spawning begins. On average, larger females held a larger number of eggs (63,500) than smaller females (14,500). By the end of the breeding season there was an average of 11,600 mature eggs per female left undeposited, regardless of female size. Larger females laid a higher percentage of the eggs they contained. Thus they not only contain more eggs, but are more effective at laying them as well. Size of spawning females ranged from about 185–300 mm prosomal width, with by far the highest concentration in the mid‐size ranges. Although on an individual basis large females carry and lay the greatest number of eggs, mid‐size crabs as a group contributed more to the horseshoe crab population in Pleasant Bay because they were more plentiful (net fecundity was highest for mid‐size crabs). These results have implications for the management of this important species, which is harvested for bait, scientific, and biomedical uses. Incorporation of these results into models and other management tools can help predict growth rates, effects of size‐selective harvest, reproductive value, and stable stage distribution of populations.  相似文献   

Airborne Laser Sensing of Scottish Coastal Waters     

Grigorii Kokhanenko  Geoff Ludbrook  Ivan Penner  Vitalii Shamanaev 《Marine Geodesy》2001,24(4):195-207

An Nd:YAG-based airborne lidar system has been used to measure the optical properties of littoral waters off the northwest Scottish coast. The small-scale structure of subsurface scattering layers was also investigated. Methods of solving the Lidar Sensing Equation in the single scattering approximation are described and the values of the derived extinction indices presented. The extinction index averaged over a series of five flights to the northeast of the Gulf Stream was ε= 0.224 m -1 with a standard deviation of 0.212 m -1 . Further, it was demonstrated that, in coastal waters, optical inhomogeneities with dimensions between 50 m and 200 km obey the power law Sp ε ~ k -P with the parameter P close to two. In turbid or transparent areas, the water extinction index can change by several tenths of a percent with respect to the surrounding water mass. This suggests that the observed nonmonotonic behavior of the power spectra of the water extinction index fluctuations is caused by the outer scale of turbulence, in particular, by the bottom depth at the measurement site.  相似文献