57Fe-Moessbauer spectra,electronic and crystal structure of members of the CuS2-FeS2 solid solution series     

Peter Schmid-Beurmann  Werner Lottermoser 《Physics and Chemistry of Minerals》1993,19(8):571-577

Members of the (Cu, Fe)S₂ solid solution crystallize in the pyrite structure type, space group Pa 3, Cu and Fe being statistically distributed on the metal sites. Within this series, a semiconductor to metal transition can be detected between 25 and 38 mole% CuS₂. Compositional dependent ⁵⁷Fe-Moessbauer spectra reveal Fe²⁺ in low-spin configuration. A minimum of the quadrupole splitting and the slope in the ⁵⁷Fe-isomer shift in the intermediate part of the system, near 30 mole% CuS₂, can be correlated with the onset of metallic conductivity, whereas the structural parameters are not influenced by this transition. The analysis of the compositional dependency of the quadrupole splitting, in comparison to the isotypic system (Co, Fe)S₂, leads to the conclusion that Cu in solid (Cu, Fe)S₂ compounds is Cu⁺ with an Ar -3 d¹⁰ electronic configuration.  相似文献   

Explorations into the formal structure of drainage basins     

Christian Werner 《地球表面变化过程与地形》1994,19(8):747-762

Every basin of higher than first order is drained by a channel network composed of two subnetworks. Their basins are separated by a drainage divide line, called the basin divider, which is the primary organizing feature of the main basin. Each basin of magnitude n contains n – 1 subnetworks of higher order, and is therefore organized by a set of n – 1 dividers. The dividers and the basin boundary are interconnected in a graph called the divider network of the basin; in graph-theoretic terms this network forms a tree and has the same magnitude and link numbers as the channel network draining the basin. While the subbasins and subnetworks of a drainage basin form a nesting hierarchy, the corresponding dividers do not; indeed, any two dividers share at most one node in common, and whether they do so is independent of whether the corresponding subbasins are nesting or disjoint. However, the dividers of nesting basins are linked by recursive relationships which permit the derivation of a set of algebraic equations; these equations relate the dividers of a basin to other basin components; for example, their combined length is equal to half the length of all first-order basin boundaries minus the length of the main basin boundary. The second part of the paper explores the dependence of the divider length on other basin parameters. The expected length, as predicted by the assumption of topological randomness, is clearly rejected by the data. An alternative approach (regression) is based on the observed magnitudes of the subbasins separated by each divider, and is reasonably successful in estimating divider length. The last section introduces the concept of the standardized basin defined by a boundary length of unity; the estimated lengths of the basin divider and the basin boundary permit an approximate reconstruction of the idealized basin shape and the location of the divider in it.  相似文献   

4He diffusion in specular hematite     

Hans J. Lippolt  Rolf S. Wernicke  Werner Boschmann 《Physics and Chemistry of Minerals》1993,20(6):415-418

In order to test the chronometer qualities of speculante for the (U + Th)/He dating method, ⁴He release experiments by stepwise heating of two specularites from the Rimbach mineralization locality in the southern Vosgues (France) have been carried out. The diffusion coefficients define linear Arrhenius plots within a temperature interval of 250 to 830 °C, which is suggestive of volume diffusion. Extrapolation of the diffusion behavior to 20° C yields diffusion coefficients (D₂₀ values) smaller than 10^?26 [cm² s^?1] for both hematites with activation energies at 116 [kJ/mole]. The results of our study suggest that specularite is a very helium retentive hematite variety which is capable of quantitatively retaining radiogenic helium over geologic periods of time.  相似文献   

Problems resulting from misinterpretations of natural resources and natural hazards in tropical countries. The example of Peru     

Werner Mikus 《GeoJournal》1985,11(1):103-109

Natural resources in a tropical country like Peru are often overestimated. Peru is characterized by a wide range of regional differences, varied physical settings, and numerous natural hazards. Some climatical and hydrological conditions are examined and the factors causing instability in agricultural and nonagricultural production are discussed. Natural resources must be evaluated in the framework of internal political, social, and economic circumstances. Several points are recommended to foster economic development when considering the constraints of the physical environment.  相似文献   

A method for quantitatively analysing dynamic recrystallization in deformed quartzitic rocks     

Brett Freeman 《Journal of Structural Geology》1984,6(6):655-661

Quantification of the microstructural changes brought about by dynamic recrystallization is essential for the interpretation of deformation mechanism histories and for the understanding of recrystallization as a syn-kinematic process. A method is presented for analysing the degree of dynamic recrystallization and for reconstructing the original grain-size distribution from that measured in the deformed specimen. This is based on size distribution measurements and comparative volume calculations between subsets of grains which contain rutile inclusions and subsets which do not. Application of the method to some quartzites from the Kilmory Bay Syncline, S. W. Highlands, Scotland, demonstrates that up to 25% of the apparent matrix grains are new grains produced by the dynamic recrystallization of porphyroclasts, and that the new grains alone compose more than 12% of the total rock volume. These figures are 2–3 times larger than estimates made by normal petrographic inspection. It is also shown that grain-size distributions alone convey little information about the microstructural changes and that grain-size vs volume fraction graphs are more meaningful.  相似文献   

Chemical equilibration of the Earth's core and upper mantle     

Robin Brett 《Geochimica et cosmochimica acta》1984,48(6):1183-1188

The oxygen fugacity (fO₂) of the Earth's upper mantle appears to lie somewhat above that of the iron-wüstite buffer, its fO₂ is assumed to have been similar to the present value at the time of core formation. In the upper mantle, the Fe-rich liquid protocore that would form under such conditions of fO₂ at elevated temperatures would lie predominantly in the system Fe-S-O. Distribution coefficients for Co, Cu, Ni, Ir, Au, Ir, W, Re, Mo, Ag and Ga between such liquids and basalt are known and minimum values are known for Ge. From these coefficients, upper mantle abundances for the above elements can be calculated by assuming cosmic abundances for the whole Earth and equilibrium between the Fe-S-O protocore and upper mantle. These calculated abundances are surprisingly close to presently known upper mantle abundances; agreements are within a factor of 5, except for Cu, W, and Mo. Therefore, siderophile element abundances in the upper mantle based on known distribution coefficients do not demand a late-stage meteoritic bombardment, and a protocore formed from the upper mantle containing S and O seems likely.As upper mantle abundances fit a local equilibrium model, then either the upper mantle has not been mixed with the rest of the mantle since core formation, or else partition coefficients between protocore and mantle were similar for the whole mantle regardless of $\text{P}$, $\text{T}$, and fO₂. The latter possibility seems unlikely over such a $\text{P-T}$ range.  相似文献   

Rates of sulfur dioxide and particle emissions from White Island volcano,New Zealand,and an estimate of the total flux of major gaseous species     

William I. Rose  Raymond L. Chuan  Werner F. Giggenbach  Philip R. Kyle  Robert B. Symonds 《Bulletin of Volcanology》1986,48(4):181-188

Airborne correlation spectrometry (COSPEC) was used to measure the rate of SO₂ emission at White Island on three dates, i.e., November 1983, 1230 ± 300 t/d; November 1984, 320 ± 120 t/d; and January 1985, 350 ± 150 t/d (t = metric tons). The lower emission rates are likely to reflect the long-term emission rates, whereas the November 1983 rate probably reflects conditions prior to the eruption of December 1983. The particle flux in the White Island plume, as determined with a quartz crystal microbalance/cascade in November 1983, was 1.3 t/d, unusually low for volcanic plumes. The observed plume particles, as shown from scanning electron microscopy, include halite, native sulfur, and silicates and are broadly similar to other volcanic plumes.Gas analyses from high-temperature volcanic fumaroles collected from June 1982 through November 1984 werde used together with the COSPEC data to estimate the flux of other gas species from White Island. The rates estimated are indicative of the long-term volcanic emission, i.e., 8000–9000 t/d H₂O, 900–1000 t/d CO₂, 70–80 t/d HCl, 1.5–2 t/d HF, and about 0.2 t/d NH₃. The long-term thermal power output at White Island is estimated at about 400 MW.  相似文献   

Dynamic behaviour of rigid foundations of arbitrary shape on a halfspace     

Werner Rüucker 《地震工程与结构动力学》1982,10(5):675-690

An approximate method for computation of the compliance functions of rigid plates resting on an elastic or visco-elastic halfspace excited by forces and moments in all degrees of freedon is presented. The method is based on a Green's function approach. These functions are given for all degrees of freedom in form of well-behaved integrals. The numerical procedure is described and is used to evaluate the vertical, horizontal, rocking and torsion compliance functions of rectangular plates with side ratios 1 ≤ b/a ≤ 10 and non-dimensional frequency 0≤a₀≤10. It is shown how this method can be extended to problems concerning a linear visco-elastic halfspace and a halfspace with variable stiffness.  相似文献   

Behavior of diorite under impact by variously-shaped projectiles   总被引：1，自引：0，他引：1  

Akihiko Kumano  Werner Goldsmith 《Rock Mechanics and Rock Engineering》1982,15(1):25-40

SummaryBehavior of Diorite Under Impact by Variously-Shaped Projectiles The effects of striker diameter and tip geometry on the crater and crack network produced in diorite by normal projectile impact in the energy range from 4–30 J was investigated. Ejecta kinematics were determined by high-speed photography; elastic strain wave propagation was measured by embedded gages in a composite specimen; and the damage pattern was ascertained from an examination of the sectioned specimen. It was found that the projectile nose shape exerts a strong influence on the shape of the elastic transient, on the crater geometry, on the extent of the crack network and on the average size of the ejecta. The crater depth was found to be the most repeatable parameter in identical tests using the same striker and initial kinetic energy.With 7 Figures  相似文献   

Carbon-13 exchange between CO₂ and CH₄ under geothermal conditions     

Werner F. Giggenbach 《Geochimica et cosmochimica acta》1982,46(2):159-165

On the basis of recently reported data on the kinetics of carbon-13 exchange between CO₂ and CH₄ at temperatures above 500°C, first order rate constants $\text{log k = 11.16?10,190/T}$ were derived allowing variations in Δ, the difference in the isotopic composition of coexisting CO₂ and CH₄, to be evaluated as a function of initial composition and cooling rate of the rising geothermal fluid. Observed Δ-values in geothermal discharges are likely to represent frozen in compositions attained after minimum residence times of 20 ka at 400°C or 10 Ma at 300°C. The carbon-13 contents of any biogenic gases are unlikely to have been affected by thermal re-equilibration at temperatures below 200°C. The chemical equilibrium involving CO₂ and CH₄ can be expected to proceed about a hundred times faster than isotopic equilibration.  相似文献