Preliminary results obtained with a vertical strainmeter at the underground laboratory of geodynamics at walferdange (grand-duchy of Luxembourg)     

P. Melchior  B. Ducarme  J.M. Van Gils  J. Flick  C. Denis 《Physics of the Earth and Planetary Interiors》1974,9(2):97-100

A new vertical strainmeter is described. An harmonic analysis of earth tides measured with that instrument has been performed. It yields a numerical estimation of the first Love number derivative which seems to be compatible with the Poisson coefficient of the local rocks of approximately 0.4.  相似文献   

Quantitative Imaging of Stable Isotopes by Ion Microprobe     

Jérôme Aléon  Marc Chaussidon  Michel Champenois  Denis Mangin 《Geostandards and Geoanalytical Research》2001,25(2-3):417-429

A new analytical procedure has been developed to measure oxygen isotopic ratios and, more generally, stable isotopic ratios in microparticles with a few % precision. This procedure uses ion microprobe quantitative imaging with a scanning microbeam. In this mode, ion images are acquired on the electron multiplier. Image processing allows extraction of areas of interest from the whole image and computation of isotopic ratios in the selected areas. The accuracy of this method has been tested for the analysis of the 18O/16O ratio in quartz and magnetite reference samples powdered to a grain size of 2-5 μm. A detailed study of the instrumental mass fractionation allowed an understanding of differences between classical spot analysis and scanning ion imaging, and showed that fractionation effects were related to grain topography for microparticle analysis, and to image processing or to secondary optical settings for ion imaging. The precision obtained for the measurement of ä18O was 3% for grains having a diameter of 2 μm.  相似文献   

The origin of laminated and massive anorthosite,Sept Iles layered intrusion,Québec,Canada     

Michael Denis Higgins 《Contributions to Mineralogy and Petrology》1991,106(3):340-354

Well-laminated plagioclase-rich rocks (‘anorthosite’) occur as layers in mineralogically similar but massive rocks in the Sept Iles intrusion. Several phases of crystallization of poikilitic clinopyroxene have preserved the intermediate stages in the production of these rocks. Plagioclase nucleated and initially grew in random orientations in the stationary part of the boundary layer. There, in the absence of other events, crystallization produced the massive anorthosite. The laminated anorthosite may have been produced by episodic increases in the velocity of the magma adjacent to the boundarylayer induced by magmatic density-currents. Such currents would have caused the zone of simple shear of the boundary-layer to migrate outwards into the previously stationary part. This simple shear would then have rotated the existing plagioclase crystals, as well as crystals that nucleated at that time, towards the shear-plane. Some rocks show evidence of several periods of enhanced flow-velocities. The production of the lamination may have weakened the crystal-mush and enabled slumping to occur, producing folds and contorted layers. Finally, compaction liberated large quantities of intercumulus magma of which some was trapped as granophyric segregations and some escaped by overturing and churning the crystal-pile. Earlier-formed granophyric segregations and laminated layers were disrupted during this process to produce a range of more-complex rocks including igneous breccias.  相似文献   

Variations in geometric measures of topographic surfaces underlain by fractured granitic plutons     

Denis Norton  Steve Sorenson 《Pure and Applied Geophysics》1989,131(1-2):77-97

Silicate melts impose systematic fracture patterns on their hosts and their own subsolidus portions as they crystallize and cool to ambient conditions. Weathering of these plutonic bodies accentuates the fractures and produces fragmented topographic surfaces whose geometric measures exceed those of a Euclidean surface. Because geometric measures of these surfaces are potentially indicative of the percolation properties of the fracture network, contours and vertical sections were digitized from 1250000 and 1240000 scale maps, and their statistical fractal dimensions,D, were computed. Regions underlain by granitic plutons with similar fragmentation patterns were found to haveD values ranging from 1.15 to 1.28 within a single pluton. This range of values is caused by noise and several geologic factors. The values contain noise introduced by the map-making and digitizing procedures that amounts toD1.05. However all values lie well above this threshold, and they correlate closely with local differences in weathering. SmallerD values derive from contours where accumulation of screen or glacial erosion has smoothed the surface, whereas largerD values derive from contours along aretes and in unglaciated terrains. In each of these regions, largerD values occur locally where fractures are most frequent and/or continuous. LargeD values were also derived from regions underlain by host rocks that lie in the near-field region of the stress field caused by the pluton. The fractral values derived are apparently related to the magma-hydrothermal event, they can potentially be used to derive properties of the percolation networks that were active during the hydrothermal events.  相似文献   

Lunar magnetic variations     

Denis E. Winch 《Pure and Applied Geophysics》1989,131(3):533-549

Displayed daygraphs of magnetic observatory hourly mean values and of lunar magnetic variations reconstructed from spherical harmonic coefficients are used to illustrate the difficulties that arise in separating lunar magnetic effects from those associated with the 27 day recurrence tendency in magnetic activity.  相似文献   

Comment on “Applications of spatial filter theory to kriging” by James R. Carr     

Denis Marcotte 《Mathematical Geosciences》1992,24(5):567-571

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Melting and premelting of silicates: Raman spectroscopy and X-ray diffraction of Li2SiO3 and Na2SiO3     

Pascal Richet  Bjorn O. Mysen  Denis Andrault 《Physics and Chemistry of Minerals》1996,23(3):157-172

The isostructural lithium (Li₂SiO₃) and sodium (Na₂SiO₃) metasilicates have been investigated from room temperature up to the melting point by single-crystal Raman spectroscopy and energy-dispersive X-ray powder diffraction. The unit-cell parameters and Raman frequencies of Li₂SiO₃ vary regularly with temperature up to the melting point, which is consistent with the lack of premelting effects in calorimetric measurements. In contrast, Na₂SiO₃ undergoes a transition at about 850 K from orthorhombic Cmc 2₁ symmetry, to a lower symmetry (possibly Pmc 2₁), and shows near 1200 K changes in the Raman spectra that correlate well with the premelting effects as determined from calorimetry observations. In both compounds, a high alkali mobility likely sets in several hundreds of degrees below the melting point. Premelting in Na₂SiO₃ is associated with extensive deformation of the silicate chains as evidenced near the melting point by similarities in the Raman spectra of the crystalline and liquid phases.  相似文献   

Trace element behaviour during anatexis in the presence of a fluid phase     

Denis M. Shaw 《Geochimica et cosmochimica acta》1978,42(6):933-943

If anatexis takes place in the presence of an immiscible volatile-rich fluid phase, the behaviour of a trace element depends not only on partition coefficients D^{i ?} between mineral i and silicate liquid, but also on coefficients D^{i f} between mineral i and fluid. The limited experimental data available, as well as theoretical arguments, suggest that for common minerals these coefficients differ, in some cases (REE) notably.Theory has been developed to permit calculation of concentration variations with the fraction F of rock melted, if D-values are known. In its present state this theory neglects the influence of T, P and composition variations in liquid and fluid on the D-values: if such variations can be expressed as functions of F, appropriate modifications can be made. The theory also neglects the effects of T and P on the solubility of fluid in liquid and the resulting modifications to phase petrology, by assuming simply that a given mass of rock melts in the presence of a mass proportion v of fluid. By choosing different values of v, from 0 (dry melting) to 100 (large fluid excess), the response of the trace element concentrations can be followed, beginning with concentration c_o in the unmelted rock. Such treatment is highly idealised, but serves to indicate some limits on what can occur.  相似文献   

Geomagnetic multipoles, 1965.0     

Denis E. Winch  Leonidas Slaucitajs 《Pure and Applied Geophysics》1966,65(1):95-101

Summary Following the recent appearance of spherical harmonic coefficients for the potential of the geomagnetic field for epoch 1965.0, the strengths and axes for a dipole, quadrupole and octupole have been computed from first, second and third order spherical harmonic coefficients respectively. An interesting relation existing between the parameters of the dipole, quadrupole and geomagnetic eccentric dipole is also indicated.  相似文献   

Wave energy losses in intermediate depths     

Denis Mollison 《Applied Ocean Research》1983,5(4):234-237

Recent work on wave power devices has encouraged interest in the processes whereby waves lose energy and change direction in shoaling water, and especially in detailed calculations of their effects.^1,2 Here one of the most comprehensive sets of measurements available is examined, for four sites in depths of 15 to 100 m off South Uist in the Hebrides. The mean directional spectrum is recalculated for each site, and a proper allowance found for refraction which raises the estimates of net energy flux in intermediate depths by up to 10%. Indeed, the pattern of losses between 100 m and 23 m depths fits well with that expected from bottom friction. The estimated friction coefficient is quite high, as might be expected in view of the very rough sea bottom in the area.³  相似文献