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381.
Summary Boron-doped mullites were synthesized using aluminium nitrate-nonahydrate, tetraethoxysilane and boric acid in a sol–gel process
with subsequent annealing at 950 and 1300 °C for five hours. Two different bulk compositions with constant Al2O3 contents (60 and 70 mol%, respectively) and varying SiO2 plus B2O3 contents were investigated. X-ray powder diffraction analyses yielded a linear decrease of the lattice parameters with increasing
bulk B2O3 content, which was interpreted as to be due to boron incorporation. Related to the increasing boron content, corresponding
infrared spectra revealed a slight and continuous shift for most of the absorption bands. These data show that mullite is
able to incorporate large amounts of boron into its structure (up to about 20 mol% B2O3 depending on the bulk composition of the starting materials). Infrared analyses suggest that boron is incorporated into the
mullite structure in form of planar three-fold coordinated BO3 groups.
Author’s address: A. Beran, Institut für Mineralogie und Kristallographie, Universit?t Wien-Geozentrum, Althanstra?e 14, 1090 Wien, Austria 相似文献
382.
M. Mejías J. Garcia-Orellana J. L. Plata M. Marina E. Garcia-Solsona B. Ballesteros P. Masqué J. López C. Fernández-Arrojo 《Environmental Geology》2008,54(3):521-536
A methodology for the characterization of deep carbonate aquifers has been developed and applied to El Maestrazgo Jurassic
aquifer in Castellón, Spain. Characterization of these aquifer formations, located at more than 300 m deep, consisted of a
previous phase of compilation, analysis and synthesis of the existing information about the area, followed by a coordinated
combination of different speciality studies: geology, stratigraphy, structural analysis, hydrogeology, hydrochemistry, geophysics
and remote sensing. Geological studies included geological mapping, definition of stratigraphical units and facies and structural
analysis. The aim of the hydrogeology study was to define aquifer formations, recharge area, aquifer points inventory and
groundwater flow directions for the establishment of piezometric and water quality observation nets. Special techniques were
applied, like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium
isotopes. Hydrochemical techniques, including majority elements characterization and stable isotopes (18O, 2H and 3H) determination, allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system.
Geophysics was useful in determining the aquifer geometry, the features of the basement and the petrophysical characteristics
of the geological formations. Preliminary results show an important tectonic complexity and the possibilities for groundwater
uses in the area of study. 相似文献
383.
384.
J. W. Norman 《The Photogrammetric Record》1968,6(32):133-149
The geologist's use of air photographs and the characteristics studied by photogeologists are briefly described. The influence of photographic factors such as scale, season, time of day, film type, processing, overlap and dimensional accuracy are considered from the geologist's viewpoint. 相似文献
385.
Photogrammetric methods using sequential aerial photography can provide the geomorphologist with comparative measurements of rapidly changing glacial landforms. Examples are given of eskers, kame and kettle areas, an ice-dammed lake and coastal features in south-east Iceland. 相似文献
386.
387.
The historical development of analytical aerial triangulation block adjustment is mentioned by way of introduction. The advantages of separating the plan and height adjustments are given and the observation equations of a typical adjustment section are analysed to show that this convenient practice is justified in normal circumstances. The principles of a direct solution of the normal equations suitable for a moderate-sized computer, are explained and developed in detail for the height adjustment. The advantages of tie-strips in the height adjustment are demonstrated and the difficulties which then arise are discussed. An approximate method which overcomes these difficulties is developed. Details of the computer programmes used are given in Appendix B. 相似文献
388.
This study of a part of the lower Critical Zone, Farm Ruighoek,Western Bushveld, is based mainly on selected drill core samplesfrom two sections approximately 1.2 miles apart. The 1300-ftsequence investigated consists of pyroxenites with two harzburgitebands and sixteen chromitite seams. Results obtained are consistent with the hypothesis that evolutionof the sequence was a cyclic process in which cumulate mineralscrystallized in a zone near the floor of accumulation undergenerally quiescent conditions. Compositional changes of cumulateminerals reflect the influence of a separate intrusion of undifferentiatedparent magma or refusion at depth of crystals formed near thetop of the magma chamber. Interstitial mineral content and plagioclasecomposition reflect changing rates of crystal accumulation.Orthopyroxene grain size and sorting coefficient reflect, inpart, the vertical distance over which crystallization occurred.Textural features and contact relations of chromitite seamsare consistent with the hypothesis that most chromite crystallizedfrom the silicate magma and accumulated during a period of littleor no crystallization of silicate minerals. It is postulatedthat this loose crystal assemblage was enriched by co-accumulationand partial in situ crystallization of chromite-rich immiscibleliquid. Textural, mineralogical, and compositional changes infootwalls and hanging walls of chromitite seams are thoughtto reflect in situ reactions. 相似文献
389.
The Strathcona iron-nickel-copper sulfide ore deposit lies atthe base of the Sudbury Nickel Irruptive along the north rimof the Sudbury basin. In the vicinity of the deposit the mainbody of the Nickel Irruptive consists of an upper unit of 3700ft (1200 m) of granophyre (the micropegmatite)and a lower unit of 1500 ft (500 m) of augite norite (the felsicnorite) separated by 300 ft (100 m) of transitional rock(the transition zone). Two augite norite intrusions(the mafic norite and the xenolithic norite)that are younger than the felsic norite occur along its lowercontact. The xenolithic norite is relatively rich in xenolithsand grades downwards into a unit known as the hanging-wallbreccia. The breccia resembles the xenolithic noritebut contains a higher proportion of xenoliths. A quartz-plagioclase-augite gneiss (the footwall gneiss)underlies all units of the Nickel Irruptive. A cataclastic breccia(the footwall breccia) which formed as a resultof comminution of both gneiss and overlying Irruptive rocksis present in most areas between the gneiss and the Nickel Irruptive.The ore body occurs partly as a dissemination of sulfides inthe matrix of the hanging-wall breccia (hanging-wallore), partly as a fine dissemination and massive stringersof sulfide in the footwall breccia matrix (main-zoneore), and partly as massive stringers of sulfide in thefootwall gneiss (deep-zone ore). Xenoliths in the xenolithic norite and hanging-wall brecciarange from dunite to olivine gabbro. Olivine in the xenoliths(composition estimated by an X-ray method) varies from Fo73to Fo85, and hypersthene and augite (composition estimated byelectron microprobe analysis) vary from Fs25 to Fsi3, and Fsi3to Fs5, respectively. The iron content of the mafic mineralsshows a positive correlation with the proportion of felsic mineralsin the xenoliths, suggesting that the xenoliths have been derivedfrom a cryptically layered body of mafic and ultramafic rock.The wide distribution of xenoliths around the margin of theNickel Irruptive coupled with the absence of any obvious externalsource is strong evidence that the xenoliths are cognate, supportingWilson's (1956) proposal that the Irruptive is a funnel-shapedintrusion with a zone of ultramafic rocks towards its base. Hypersthene ranges from Fs33 to Fs28 in the felsic norite, fromFs28 to Fs22 in the mafic norite, and from Fs28 to Fs20 in thexenolithic norite. Augite ranges from Fsl6 to Fs14 in the felsicnorite and from Fs14 to Fsn in both the mafic and xenolithicnorites. The distribution coefficient for iron and magnesiumbetween coexisting augite and hypersthene ranges from 1-0 insome of the xenoliths to 1-5 in some samples of felsic norite,indicating that the two pyroxenes equilibrated at, or near,magmatic temperature. The composition of plagioclase in thefelsic norite, mafic norite, and xenolithic norite is aroundAn65-70 but decreases to An44 in those Irruptive rocks closestto the footwall breccia. The composition of plagioclase withinthe breccia varies between An32 and An43. Sodium metasomatismappears to have affected the breccia and to have spread outto affect adjacent rocks. The concentration of nickel and copper in the sulfides variessystematically across the ore deposit. The nickel content ofiron-nickel sulfides varies between 2-5 and 3 per cent in thehanging-wall ore but increases regularly from 3 per cent to5 or 5-5 per cent from hanging wall to footwall across the main-zoneore. Copper concentration shows a similar but more erratic variation.The variation is attributed to thermal diffusion of nickel andcopper within the main-zone ore along a gradient induced bythe overlying, hot, Nickel Irruptive. The principal opaque minerals in the ore body are, in the orderof their abundance, pyrrho-tite of at least two types, magnetite,pentlandite, chalcopyrite, and pyrite. All of the sulfides inthe hanging-wall ore are the result of exsolution from a high-temperature,pyrrhotite solid solution. Pyrite started to exsolve below 700C, chalcopyrite below 450 C, and pentlandite below 300 C.Monoclinic pyrrhotite formed from the host hexagonal pyrrhotiteprobably between 300 and 250 C. The temperature of formationof the sulfides in the main-zone ore has been obscured by reworkingof the ore after its first emplacement. The principal ore sulfides, pyrrhotite and pentlandite, arecommon throughout the mafic norite, xenolithic norite, and hanging-wallbreccia, occurring in amounts around 5 per cent in most samples.Pyrrhotite and pentlandite are extremely rare in the overlyingfelsic norite where pyrite is the most common sulfide. It occursin amounts between 01 and 0-5 per cent, commonly together withsecondary amphibole after pyroxene. The sulfides in the maficand xenolithic norites and in the hanging-wall breccia occupyspaces interstitial to the silicates, and little or no replacementof silicates by sulfides has occurred. In the main-zone ore,evidence of small-scale replacement of silicates by sulfidesis common. The high percentage of pyrrhotite and pentlandite in the maficand xenolithic norites in contrast to the felsic norite, texturalrelations between sulfides and silicates, and the high temperaturesindicated by the pyroxene distribution coefficients lead tothe conclusion that the hanging-wall sulfides (including thehanging-wall ore) at Strathcona were introduced with these youngernoritic intrusions. Data on the solubility of sulfides in silicatemagmas rule out the possibility that the bulk of the sulfideswere in solution in the noritic magmas; the data support thehypothesis that during intrusion the sulfides were held in suspensionin the in the magmas as droplets of immiscible sulfide-oxideliquid. Calculations on the rate of settling to be expectedfor such sulfide droplets are consistent with this hypothesis.The manner of emplacement of the main-zone ore is less certain;our explanation is that this ore consists of sulfides that originallysettled out of, or collected along, the base of the hanging-wallbreccia zone and were subsequently incorporated in the brecciationthat gave rise to the footwall breccia. The origin of the sulfides at Strathcona is clearly connectedclosely with the origin of the younger noritic intrusions. Asimilar connexion exists between sulfides and young marginalintrusions at many other Sudbury deposits. Jt is possible thatboth sulfides and intrusions are portions of the Nickel Irruptivemagma that lagged behind the main body of magma and were intrudedat a later stage. Alternatively, the young intrusions may haveassimilated sulfides from a sulfide-rich zone within or at themargin of the deeper layers of the Irruptive. 相似文献
390.
J. Bhattacharya 《Pure and Applied Geophysics》1962,52(1):1-6
Summary
Kisslinger and others have observed that there is strongSH-motion in clay resulting in fracture of the surface when a strong shot is made inside. To explain this phenomenon, it has been assumed that the thickness of this visco-elastic clay above the comparatively harder elastic medium is not uniform. This non-uniformity of thickness contributes to a term in the displacement which becomes theoretically very large for certain wave-lengths. 相似文献