The effect of feldspar on quartz-H2O−CO2 dihedral angles at 4 kbar,with consequences for the behaviour of aqueous fluids in migmatites     

Marian B. Holness 《Contributions to Mineralogy and Petrology》1995,118(4):356-364

An investigation was made of the effect of trace amounts of feldspar (Na and/or K) on dihedral angles in the quartz-H₂O-CO₂ system at 4 kbar and 450–1050°C. Quartz-quartz-H₂O dihedral angles in feldspar-bearing quartz aggregates are observed to be the same as those in pure quartz aggregates at temperatures below 500°C. Above this temperature, they decrease with increasing temperature until the solidus. The final angle at the inception of melting is about 65° for microcline-quartz-H₂O and microcline-albite-quartz-H₂O, and much less than 60° (the critical value for formation of grain-edge fluid channels in an isotropic system) for the albite-quartz-H₂O system. CO₂ was observed to produce a constant quartz-quartz-fluid dihedral angle of 97° in feldspar-bearing quartz aggregates at all temperatures studied. Also examined were the dihedral angles for the two co-existing supersolidus fluids in quartz aggregates. In all systems the quartz-volatile fluid angle is greater than 60°, whereas the quartz-melt angle is lower than 60°. Both super-solidus angles decrease with increasing temperature. The transition from nonconnected to connected poro- sity with increasing temperature observed in the quartz-albite-H₂O system some tens of degrees below the solidus (termed a permeability transition), if a common feature of rocks near their melting points, will play an important role in controlling the permeability of high-grade rocks to aqueous fluids. Received: 27 October 1993 / Accepted: 11 July 1994  相似文献   

Bayesian Decision Analysis for Plume Interception Wells     

Hewa A. Wijedasa  Marian W. Kemblowski 《Ground water》1993,31(6):948-952

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Dynamic response of single-span beam bridges to a series of moving loads     

Marian Klasztorny  Jan Langer 《地震工程与结构动力学》1990,19(8):1107-1124

The paper makes a contribution to the problem of a stream of loads crossing a single-span beam bridge. There are considered the basic load models, in the form of a stream of fixed amplitude forces, unsprung masses and viscoelastic oscillators. The matrix equations of motion of the system are formulated and discussed. The problem of dynamic stability and steady-state response of a bridge carrying a periodic stream of inertial loads is formulated and solved. The paper also includes a vibration study of a beam bridge subjected to a uniform stream of moving loads, of a limited or unlimited number of load cycles.  相似文献   

Digital mapping of riverine waterway hydrodynamic and geomorphic features     

A. Hauet  M. Muste  H‐C. Ho 《地球表面变化过程与地形》2009,34(2):242-252

This paper proposes an innovative, non‐intrusive method for mapping waterway characteristics in riverine areas. The technique uses photogrammetry to provide quantitative information about the dry area in the vicinity of the waterways (banks and floodplain) and image processing algorithms to characterize the flow. Riverside images of a riverine area are decomposed into quasi‐planar areas and ortho‐rectified and re‐assembled to obtain a panoramic ortho‐view of the area of interest. Morphological features of interest (such as river bank positions, flood plain edges, mud deposits, vegetation and erosion patterns) are then identified on the ortho‐view and mapped digitally. Image sequences of the river flow are recorded, allowing a surface velocity analysis to be obtained through Large Scale Particle Image Velocimetry (LSPIV). Finally, the mapped elements and the surface velocities are displayed together in a GIS‐like visualization. Through the presentation of a case study of a flood event at a culvert site, this paper demonstrates the capability of the technique to monitor characteristics of waterways over time. The method is inexpen‐sive (a conventional video or digital camera can be used), fast and requires minimum preparation. It can be applied in such important river‐related research areas as morphodynamic and sediment transport studies. It also fosters an improved understand‐ing of the coupling between the river and its banks, which is essential for river restoration and eco‐habitat studies. The present methodology is readily available for implementation in routine bridge inspections, fitted with an easy‐to‐use graphical interface. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Reply to comment by W.U. Reimold, R.L. Gibson, and H. Henkel on Muundjua et al. (2007), “Magnetic imaging of the Vredefort impact crater, South Africa”, EPSL 261, pp 456–468     

Manfriedt Muundjua  Armand Galdeano  Laurent Carporzen  Stuart A. Gilder  Rodger J. Hart  Marco A.G. Andreoli  Marian Tredoux 《Earth and Planetary Science Letters》2008,273(3-4):397-399

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Plasma Resonance Surfaces in the Magnetic Field Reconnection and Radio Fine Structures     

Karlický  Marian 《Solar physics》2003,212(2):389-400

Using a 2-D MHD model, the magnetic field reconnection in the current sheet and corresponding plasma resonance lines (surfaces in 3-D), where the upper-hybrid frequency equals one of harmonics of the electron gyrofrequency, _UH=(_pe ²+_Be ²)^1/2=s_Be (_UH, _pe, and _Be are the upper hybrid, electron plasma, and cyclotron frequencies, respectively, and s is the integer harmonic number) are computed. Then at selected times and positions in the magnetic reconnection the spatial and time spectra of upper hybrid frequencies along the resonance lines are calculated. These spectra are discussed from the point of view of radio fine structures as narrowband dm-spikes, zebras, and lace bursts. It is shown that not only turbulent plasma outflows, suggested in the paper by Bárta and Karlický (2001), but also perturbed zones near the reconnection slow-mode shocks can be locations of the narrowband dm-spikes (and/or continua). Sources of the lace bursts (i.e. bursts with irregular lines) can be located in the reconnection space, too. On the other hand, the zebras (bursts with regular separations of zebra lines) need to be generated out of strongly perturbed reconnection areas.  相似文献   

Transboundary flow modeling: the Zohor depression of Austria and the Slovak Republic     

Fendek M  Fendekova M 《Ground water》2005,43(5):717-721

Estimation of available ground water is a basic aspect of ground water management. Mathematical modeling is one of the methods that can be effectively used to obtain such estimates. A numerical model was used to calculate available ground water in the Zohor depression-an aquifer transcending national boundaries between the Slovak Republic and Austria. The aquifer, formed by Quaternary sediments overlying Neogene sequences, is composed of various clays interbedded with layers of sand, gravel, sandstones, and conglomerates. The AQUA computer model package was used to simulate flow in the aquifer. For model compilation, the following data were used: (1) effective precipitation; (2) surface water levels in surface water gauging profiles; and (3) withdrawal amounts. Hydraulic parameters of the aquifer were estimated based on information from 86 wells located in the area. The model was verified using data on ground water levels from a monitoring network. The simulation of the aquifer system permitted the estimation of the available ground water in the study area, showing that an additional 587 L/s can be abstracted. Ground water inflows to the Morava River, which flows through the region, range from 745 to 3100 L/s.  相似文献   

Textural Maturity of Cumulates: a Record of Chamber Filling, Liquidus Assemblage, Cooling Rate and Large-scale Convection in Mafic Layered Intrusions   总被引：1，自引：0，他引：1  

Holness  Marian B.; Nielsen  Troels F. D.; Tegner  Christian 《Journal of Petrology》2007,48(1):141-157

Textural maturity describes the extent to which a rock has evolvedfrom the initial reaction-controlled texture towards texturalequilibrium controlled by the minimization of interfacial energy.Solidification in a magma chamber results in the formation ofan impingement texture by the random juxtaposition of planar-sidedgrains. Orthocumulates, in which the initial melt-filled poresare pseudomorphed by later-crystallizing phases, have an ophiticor intersertal texture immediately after complete solidification,which then evolves towards solid-state equilibrium by roundingof initially planar grain boundaries and an increase in themedian dihedral angle subtended at the junctions of two primocrysticgrains with the interstitial phase. The bulk of the increasein angle occurs just below the solidus temperature in kilometre-scalemafic plutons. Quantification of textural maturity via measurementof dihedral angle populations in troctolitic and gabbroic cumulatesfrom the Rum Eastern Layered Intrusion and the Skaergaard Intrusiondemonstrates that the rocks preserve a record of thermal eventsrelated to magma chamber replenishment and the onset of chamber-wideconvection. Textural maturity is also a function of the liquidusphase assemblage: for systems in which only olivine and plagioclaseare liquidus (i.e. cumulus) phases in the main magma body abovethe crystal mush, the texture is significantly less mature thanthat in systems in which clinopyroxene is an additional liquidusphase. The difference in textural maturity reflects differencesin the cooling and solidification rate, and demonstrates directlythat the liquidus phase assemblage plays a role in determiningthe thermal history of plutons. KEY WORDS: cumulates; dihedral angles; Rum; Skaergaard; textures  相似文献   

Textures in Partially Solidified Crystalline Nodules: a Window into the Pore Structure of Slowly Cooled Mafic Intrusions   总被引：2，自引：0，他引：2  

Holness  Marian B.; Anderson  Alfred T.; Martin  Victoria M.; Maclennan  John; Passmore  Emma; Schwindinger  Kathleen 《Journal of Petrology》2007,48(7):1243-1264

Abundant glass is present along grain boundaries in coarse-grained,glass-bearing, crystalline gabbroic and peridotitic nodulesentrained and erupted in lavas from Iceland, Santorini and MaunaLoa (Hawaii), even when the total porosity is less than a fewvolume per cent. The glass films vary from a few microns toa few tens of microns thick, and are associated with stringsof small lensoid grain boundary pockets formed by impingementduring crystal growth. Additional porosity occurs as extensiveliquid-filled pockets adjacent to included grains within oikocrystsand as large triangular pockets formed by impingement of planar-sidedgrains. Interstitial material within glass films, and the irregularityof film thickness along a single grain boundary, suggest thatthe present pore structure is representative of the pore structurebefore entrainment and eruption. Pore geometry is consistentwith a dominant control by crystal growth during solidification,with little or no evidence for control by minimization of internalenergies driven by textural equilibration. Similarities betweenliquid distribution in the crystalline nodules and that of late-stage,interstitial phases in fully solidified mafic cumulates fromthe Rum and Skaergaard intrusions demonstrate that the crystallinenodules provide information about the latest stages of solidificationin slowly cooled mafic plutons. The highly permeable networkof intersecting liquid films, lenses and pockets may promotein situ crystallization in the solidifying mush, explainingthe common presence of adcumulates in such intrusions. KEY WORDS: textures; liquid distribution; mafic cumulates; crystalline nodules  相似文献   

The Almahata Sitta polymict breccia and the late accretion of asteroid 2008 TC₃     

Marian Horstmann  Addi Bischoff 《Chemie der Erde / Geochemistry》2014

On October 7, 2008, a small asteroid named 2008 TC₃ was detected in space about 19 h prior to its impact on Earth. Numerous world-wide observations of the object while still in space allowed a very precise determination of its impact area: the Nubian Desert of northern Sudan, Africa. The asteroid had a pre-atmospheric diameter of ∼4 m; its weight is reported with values between ∼8 and 83 t, and the bulk density with ∼2–3 g/cm³, translating into a bulk porosity in the range of ∼20–50%. Several dedicated field campaigns in the predicted strewn field resulted in the recovery of more than 700 (monolithological) meteorite fragments with a total weight of ∼10.5 kg. These meteorites were collectively named “Almahata Sitta”, after the nearby train station 6, and initially classified as an anomalous polymict ureilite. Further work, however, showed that Almahata Sitta is not only a ureilite but a complex polymict breccia containing chemically and texturally highly variable meteorite fragments, including different ureilites, a ureilite-related andesite, metal-sulfide assemblages related to ureilites, and various chondrite classes (enstatite, ordinary, carbonaceous, Rumuruti-like). It was shown that that chondrites and ureilites derive from one parent body, i.e., asteroid 2008 TC₃, making this object, in combination with the remotely sensed physical parameters, a loosely aggregated, rubble-pile-like object. Detailed examinations have been conducted and mineral-chemical data for 110 samples have been collected, but more work on the remaining samples is mandatory.  相似文献