Hydrogen and oxygen isotope exchange reactions between clay minerals and water   总被引：1，自引：0，他引：1  

James R O&#x;Neil  Yousif K Kharaka 《Geochimica et cosmochimica acta》1976,40(2):241-246

The extent of hydrogen and oxygen isotope exchange between clay minerals and water has been measured in the temperature range 100–350° for bomb runs of up to almost 2 years. Hydrogen isotope exchange between water and the clays was demonstrable at 100°. Exchange rates were 3–5 times greater for montmorillonite than for kaolinite or illite and this is attributed to the presence of interlayer water in the montmorillonite structure.Negligible oxygen isotope exchange occurred at these low temperatures. The great disparity in D and O¹⁸ exchange rates observed in every experiment demonstrates that hydrogen isotope exchange occurred by a mechanism of proton exchange independent of the slower process of O¹⁸ exchange.At 350° kaolinite reacted to form pyrophyllite and diaspore. This was accompanied by essentially complete D exchange but minor O¹⁸ exchange and implies that intact structural units in the pyrophyllite were inherited from the kaolinite precursor.  相似文献   

Metallogenese im Paläozoikum der Ostalpen     

Prof. Dr. Oskar Schulz 《International Journal of Earth Sciences》1974,63(1):93-104

Zusammenfassung Nach der herkömmlichen, seit vier Jahrzehnten vertretenen und seither verschieden abgewandelten Auffassung über die Ostalpenvererzungen spielen paläozoisch entstandene Lagerstätten nur eine bescheidene Rolle. In den vergangenen fünf Jahren meldeten Kollegen aus Deutschland, Italien und österreich Bedenken gegen diese Auffassung an und berichteten von zahlreichen Metallanreicherungen, deren Ursprung paläozoisch gedeutet wird. Der Rahmen ist somit schon nach dem derzeitigen Stand der Kenntnisse beträchtlich größer und geht weit über das hinaus, was bisher als vorvariszische und variszische Lagerstätten bezeichnet wurde. Das gilt nicht nur für die Anzahl der Vorkommen und Lagerstätten, sondern auch für die Vielzahl der Paragenesen. Die Neuergebnisse beziehen sich auf Erzanreicherungen hauptsächlich mit den Metallen Fe, Cu, Mg, Sb, W, Hg und U. Diese Anreicherungen sind in mehreren zeitlichen Zyklen vom Altpaläozoikum bis Perm entstanden und wurden großteils gemeinsam mit dem Nebengestein unterschiedlich metamorphosiert.

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Deposits of paleozoic origin have been considered to be only of minor importance to the conventional concepts of mineralization in the Eastern Alps. During the past five years, however, scientists from Germany, Italy and Austria raised doubts as to the correctness of these concepts describing numerous metal enrichments presumably of paleozoic origin. Hence the number of deposits and the variety of parageneses is much greater than has hitherto been assumed. The new results refer to ores enriched mainly with the following metals: Fe, Cu, Mg, Sb, W, Hg and U. The origin of these enrichments has to be attributed to several cycles from the old Paleozoic through the Permian. They were subject to different metamorphic changes together with the accessory rock.

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Résumé Suivant l'interprétation traditionelle, soutenue et différement changée durant une période de 40 ans, parmi les minéralisations métalliques des Alpes Orientales les gisements d'âge paléozoÏque ne jouent qu'un rÔle subordonné. Dans les cinq dernières années des collègues allemands, italiens et autrichiens ont presenté des objections á cette interprétation et ont fait état des nombreuses concentrations métallifères, dont l'origine doit Être placée au PaléozoÏque. La cadre est donc dévenu, déjà dans l'état actuel des connaissances, plus large et bien plus nombreux sont les gisements qui peuvent Être considérés d'âge pré-hercynien ou hercynien. Cette conclusion est valable non seulement pour le nombre des manifestations et des gisements, mais aussi pour la multiplicité des paragenèses. Les nouveaux résultats concernent surtout les concentrations des métaux Fe, Cu, Mg, Sb, W, Hg et U. Ces concentrations ont été engendrées chronologiquement durants de nombreux cycles, du PaléozoÏque ancien au Permien, et ont été pour la plupart métamorphisées, parallèlement avec leurs roches encaissantes, à divers degrés d'intensité.

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The decay of the mean solar magnetic field     

Neil R. Sheeley Jr.  C. Richard DeVore 《Solar physics》1986,103(2):203-224

We have analyzed the effects that differential rotation and a hypothetical meridional flow would have on the evolution of the Sun's mean line-of-sight magnetic field as seen from Earth. By winding the large-scale field into strips of alternating positive and negative polarity, differential rotation causes the mean-field amplitude to decay and the mean-field rotation period to acquire the value corresponding to the latitude of the surviving unwound magnetic flux. For a latitudinally broad two-sector initial field such as a horizontal dipole, the decay is rapid for about 5 rotations and slow with a t ^–1/2 dependence thereafter. If a poleward meridional flow is present, it will accelerate the decay by carrying the residual flux to high latitudes where the line-of-sight components are small. The resulting decay is exponential with an e-folding time of 0.75 yr (10 rotations) for an assumed 15 m s^–1 peak meridional flow speed.E.O. Hulburt Center for Space Research.Laboratory for Computational Physics.  相似文献   

Vegetation history and environmental development since ca 6000 cal yr BP in and around Ispani 2 (Kolkheti lowlands,Georgia)     

Pim de Klerk  Andreas Haberl  Andreas Kaffke  Matthias Krebs  Izolda Matchutadze  Merten Minke  Jenny Schulz  Hans Joosten 《Quaternary Science Reviews》2009,28(9-10):890-910

The Kolkheti lowlands of western Georgia have a unique vegetation and a rich cultural history. Palynological and macrofossil analysis accompanied by AMS ¹⁴C-dates of the deposits of the Ispani 2 mire near Kobuleti allow the reconstruction of regional vegetation, environmental history and local peatland development within the context of Black Sea level and cultural changes. Comparison of two adjacent peatland cores confirms spatial differences in wetland development. Prior to 5400 cal yr BP, the Ispani basin was a floodplain of an active river system where overbank deposits with fluvially transported Castanea pollen were deposited. Subsequently, a lake or lagoon developed in which reeds expanded. These were succeeded by herb-rich open alder carrs. After 1900 cal yr BP, Carpinus and Fagus expanded on the dry grounds, where formerly Quercus was more abundant. Also Castanea declined. Local reedbeds, that burned regularly, succeeded the alder carr. After 1000 cal yr BP, a percolation bog developed resulting in the formation of 4 m of loose, porous, and largely undecomposed Sphagnum austinii peat with Molinia roots. The upper 50 cm of the analysed section show extensive human impact on the landscape during the 20th century.  相似文献   

Sedimentological,geomorphological and dynamic context of debris-mantled glaciers,Mount Everest (Sagarmatha) region,Nepal     

Michael J. Hambrey  Duncan J. Quincey  Neil F. Glasser  John M. Reynolds  Shaun J. Richardson  Samuel Clemmens 《Quaternary Science Reviews》2009,28(11-12):1084

This paper presents the sediment, landform and dynamic context of four avalanche-fed valley glaciers (Khumbu, Imja, Lhotse and Chukhung) in the Mount Everest (Sagarmatha) region of Nepal. All four glaciers have a mantle of debris dominated by sandy boulder-gravel that suppresses melting to an increasing degree towards the snout, leading to a progressive reduction in the overall slope of their longitudinal profile. Prominent lateral–terminal moraine complexes, also comprising sandy bouldergravel, enclose the glaciers. These terminal moraines originally grew by accretion of multiple sedimentary facies of basal glacial and supraglacial origin, probably by folding and thrusting when the glaciers were more dynamic during the Little Ice Age. The four glaciers are in various stages of recession, and demonstrate a range of scenarios from down-wasting of the glacier tongue, through morainedammed lake development, to post-moraine-dam breaching. Khumbu Glacier is at the earliest stage of supraglacial pond formation and shows no sign yet of developing a major lake, although one is likely to develop behind its >250 m high composite terminal moraine. Imja Glacier terminates in a substantial body of water behind a partially ice-cored moraine dam (as determined from geophysical surveys), but morphologically appears unlikely to be an immediate threat. Chukhung Glacier already has a breached moraine and a connected debris fan, and therefore no longer poses a threat. Lhotse Glacier has an inclined, free-draining tongue that precludes hazardous lake development. From the data assembled, a conceptual model, applicable to other Himalayan glaciers, is proposed to explain the development of large, lateral-terminal moraine complexes and associated potentially hazardous moraine dams. – 2008 Elsevier Ltd. All rights reserved.  相似文献   

The origin of the 28- to 29-day recurrent patterns of the solar magnetic field     

Neil R. Sheeley Jr.  C. Richard DeVore 《Solar physics》1986,104(2):425-429

Numerical simulations of the Sun's mean line-of-sight magnetic field suggest an origin for the 28-to 29-day recurrent patterns of the field and its associated interplanetary phenomena. The patterns are caused by longitudinal fluctuations in the eruption of new magnetic flux, the transport of this flux to mid latitudes by supergranular diffusion and meridional flow, and the slow rotation of the resulting flux distributions at the 28- to 29-day periods characteristic of those latitudes.E. O. Hulburt Center for Space Research.Laboratory for Computational Physics.  相似文献   

Simulations of baryon oscillations     

Eric Huff  A.E. Schulz  Martin White  David J. Schlegel  Michael S. Warren   《Astroparticle Physics》2007,26(6):351-366

The coupling of photons and baryons by Thomson scattering in the early universe imprints features in both the cosmic microwave background (CMB) and matter power spectra. The former have been used to constrain a host of cosmological parameters, the latter have the potential to strongly constrain the expansion history of the universe and dark energy. Key to this program is the means to localize the primordial features in observations of galaxy spectra which necessarily involve galaxy bias, non-linear evolution and redshift space distortions. We present calculations, based on mock catalogs produced from high-resolution N-body simulations, which show the range of behaviors we might expect of galaxies in the real universe. We investigate physically motivated fitting forms which include the effects of non-linearity, galaxy bias and redshift space distortions and discuss methods for analysis of upcoming data. In agreement with earlier work, we find that a survey of several Gpc³ would constrain the sound horizon at z  1 to about 1%.  相似文献   

Comments on “Japan's Direct Manufacturing Investment”     

Neil Reid 《The Professional geographer》1990,42(2):223-226

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Similarity of new palaeomagnetic data from the Santa Rosa Mountains with those from Steens Mountain gives wide regional evidence for a two-stage process of geomagnetic field reversal     

Neil Roberts  Mike Fuller 《Geophysical Journal International》1990,100(3):521-526

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Dynamically Induced Displacements of a Persistent Cold-Air Pool     

Neil P. Lareau  John D. Horel 《Boundary-Layer Meteorology》2015,154(2):291-316

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